October 18, 2025 • 32 mins
What are these little bundles of DNA we call genes and how does a bunch of genes work together to make a whole plant? In this episode we’ll take a journey through plant genetics and see why scientists have been so keen to unlock these secrets and ultimately to shape them to human ends.
References: On the history of Japanese rice research in Taiwan:
- Tracing the Roots of Taiwanese Rice. Cathy Teng, photos Chuang Kung-ju, tr. by Scott Williams July 2016
- Leow, W.Y. (2020). Horai Rice in the Making of Japanese Colonial Taiwan. Cross-Currents: East Asian History and Culture Review 9(1), 40-66.
- Wikipedia: Taiwan Under Japanese Rule
- Hedden, P., Sponsel, V. A Century of Gibberellin Research. J Plant Growth Regul 34, 740–760 (2015). https://doi.org/10.1007/s00344-015-9546-1
- RADLEY, M. Occurrence of Substances Similar to Gibberellic Acid in Higher Plants. Nature 178, 1070–1071 (1956). https://doi.org/10.1038/1781070a0
- Bernard O Phinney. By Ann Hirsch. UCLA Department of Ecology and Evolutionary Biology.
Mark as Played
Transcript
Episode Transcript
Available transcripts are automatically generated. Complete accuracy is not guaranteed.
(00:00):
Question.
(00:03):
How do you like to eat a peanut?
Before I go further, big apology to all those out there with peanut allergies.
I am truly very sorry because I love peanuts and so do most of the planet as far as I can
tell.
Optimus and Elenia of being enjoyed in South America, peanuts got the colonial treatment
and were very rapidly spread around their whole world and enjoyed everywhere.
(00:23):
The colonial connections are particularly strong in that it was enslaved Africans who
brought the peanuts to the United States.
Ask Americans today who they associate with peanuts and you'll probably get either
late President Jimmy Carter who was a peanut farmer before launching his political career
or you'll get George Washington Carver who does have a very strong claim to peanut fame
(00:44):
but country but topopular belief did not invent peanut butter.
In fact Carver was an agronomist, part of the very 20th century American project used
scientific principles to improve agriculture generally by boosting productivity with automation,
fertilization and irrigation.
Carver himself was more focused on techniques that could improve soils, particularly crop
(01:06):
rotation and in supporting black farmers to improve profits by growing crops such as peanuts
they can maybe process in a variety of ways to add value and he pursued his applied research
in community education from his position as head of agriculture at Tuskegee University
in Alabama for the first few decades of the 20th century.
Anyway, back to peanuts and eating them.
(01:29):
Maybe like me you get a little kick out of taking the peanut, sliding your nails around
until you find the place where the two halves meet and then sliding your nail into the
tiny slit as you definitely pull it apart.
Inside, tucked between the two halves is a little nodule.
It doesn't look like much just a little lump of peanut colored material.
(01:50):
If I'm eating peanuts it's likely they're roasted and salted which means they're dead.
But if you had raw peanuts you're dealing with something else, not a dead thing but a living
breathing thing, a seed that is not just full of potential life but is currently alive.
While it's just a seed at this point it's not doing anything too exciting it has very
low moisture content and the breathing already we should say molecular respiration is happening
(02:15):
at a very low rate.
A living peanut is not photosynthesizing meaning it doesn't have any green leaves to harvest
sunlight with.
But it is at a very low rate using chemical reactions to break apart sugars to produce
energy to power a baseline level of cellular processes including gene expression.
And if you were to take that peanut and put it in some damp soil with some overhead light
(02:39):
those dormant biological processes will very quickly ramp up within a few hours and then
within a few days all that hard molecular work will be easily visible to the naked eye.
The changes begin like I mentioned long before you can see them and well within a day.
The seed begins to swell and the cells and the seed coat that's the thin brown wrapping
(02:59):
around the peanut soften begin to fall away.
Not so much fall away is get ripped apart as something begins to stir from within the
peanut.
A tiny little nodule that looks like nothing very much begins to swell and grow.
A tiny protrusion just a millimeter long in the dry nut forces its way downward into
(03:21):
the soil expanding to ten times its original size over the space of a day.
This is the radical spell RADICLE.
The original root already preformed and hidden inside the embryo at the center of the
seed and at the same time as the radical is pushing downwards those two huge halves of
the peanut that surround it are undergoing some dramatic changes.
(03:45):
They're pushing outwards separating the soil around the embryo and turning light green.
Because you see what I've been calling the halves of the peanut are the cotterledans.
Often called seed leaves and yes the main body of what we consider a peanut is a set of dormant
seed leaves.
These are different from standard peanut leaves of a peanut plant and they play a specific
(04:09):
role in germination that's the process of the seed transforming into a plant.
In many plants the cotterledans push upwards after the soil and spread out to form fully
functional leaves the first leaves of the emerging plant.
But for peanuts like most plants with large seeds the cotterledans remain below ground, mostly
(04:29):
serving as a store of nutrition for the radical pushing down into the earth and for the
final crucial part of the embryo the plumeul.
The plumeul is inside the little nodule between the cotterledans just where the radical was
and it's a set of a few tiny true leaves and a stem that pushed their way up into the
light and at the top of the stem is the engine of plant growth to come the shoot apical
(04:55):
meristem.
The seed of a plant is similar to an animal embryo it has a bunch of parts in miniature
that grow but unlike an animal embryo there is no blueprint for what the final adult version
will look like.
Animals can develop totally new organs during development that is true that are not in the
original embryo but that will all happen according to a specific predetermined plan encoded in
(05:19):
the genes of the embryo cells.
A plant doesn't develop according to a predetermined plan in the same way.
We say that they have indeterminate development, they have a kit of parts leaves roots branches
flowers and the exact number size and relationship between all these will develop in response
to the environment and can continue to change over the whole lifetime lifespan of the plants.
(05:44):
Well that does differ a bit from plant to plant some oversimplifying a little.
Some plants do tend to reach a particular end size before reproducing and dying but still
there will be lots of variation in how they get to that end point the exact number and
arrangement of organs they produce along the way.
And facilitating that indeterminate dynamic development are a special pair of organs the
(06:05):
shoot apical meristem above and root apical meristem below.
These organs are patches of dynamic dividing cells and not just dividing but differentiating
as they do so.
The meristem always remains through the life of the plant always as a sensor of dividing
cells being carried higher and higher or deeper and deeper down as it leaves behind it a trail
(06:27):
of differentiated plant organs.
We animals don't have this sort of developmental dynamism.
We do have some pools of constantly dividing and differentiating cells.
In humans the most obvious example is that for our whole lives we have pockets of what are
called stem cells in our bone marrow, constantly dividing with the daughter cells they produce
differentiating into all the different types of blood cells.
(06:51):
How can one stem cell in our bone marrow produce all the different types of blood cells?
And how can the apical meristem cells in a grown plant produce every possible organ of the
adult plant?
It's possible because every cell in an organism contains the whole genome.
So within each cell is the full complement of genes accessible within the nucleus to an
army of proteins that can process information from the outside and use that information
(07:15):
to select the most advantageous genes to turn on and off and in doing so trigger a few
of the cells from the meristem to form a new branch here or a new root there or if the timing
is perfect to produce a flower.
Inside the meristem cells the genes are very busy indeed.
The nucleus is thrombing with life, the DNA is feld and unfurled, proteins called transcription
(07:38):
factors are searching along the DNA without hands, without eyes, but guided by the laws of
thermodynamics till they find the right DNA sequence.
Once they found the right DNA sequence they stop moving around and stay in place long enough
to recruit the master of ceremonies RNA polymerase.
That's the mega protein complex that runs along the DNA, scanning it and using it to create
(08:00):
messenger copies of the sequence made of RNA, the nimble sister of DNA.
RNA can leave the nucleus and head off into the cytoplasm of the cell, waiting in the cytoplasm
is another type of mega complex, the ribosome.
In order to make sure the protein is specialized RNA molecules the ribosome has a cavity
in the side that accepts the messenger RNA molecule freshly arrived from the nucleus.
(08:24):
The messenger RNA is fed through the ribosome with the codenance RNA red to produce a protein
with a specific amino acid sequence.
When we talk about genetic code being read in a cell this is really what we mean.
The RNA polymerase creates an RNA version of the gene and the ribosome reads the RNA version
of the original DNA code without a brain it understands the message overseeing the assembly
(08:49):
of a new protein molecule following the precise instructions that lay within the RNA molecule
which come directly from the original DNA master copy.
Once the ribosome has done its thing the new protein molecule is ready to begin its life.
It may live for just a few minutes or it may live for years.
It may be a piece of a fibosel that will form the internal structure for the cell.
(09:11):
It may be one of the hundreds of proteins that facilitate the harvesting of sunlight to
produce energy.
It may be an aquaporin, a type of protein that sits in the cell membrane, the fatty barrier
that separates the inside from the outside of the cell.
Given the right cues it lets water rush in forcing the cell to expand, a crucial part
of all the growth processes we've described.
(09:33):
It could itself be a transcription factor destined to head back into the nucleus to join
the dance of DNA, firling and unfirling, scanning and reading.
None of this could happen outside the context or the environment the seed finds itself in,
the water, the sunlight, the minerals in the soil, the bacteria and fungi that surround
(09:54):
the seed.
In the case of our thought experiment, you the human who placed it in the soil are a
crucial environmental factor.
These environmental factors are actively sensed and responded to by the cells in the growing
plant with corresponding changes in gene expression.
In a sense the genes are the locus of information processing, with all this complex information
(10:17):
about the external environment, the internal condition and position of the cell all processed
into changes to the expression of the several thousand genes in the nucleus.
Genes are a physical scaffold within the cell, on which information processing can happen.
They allow for computation, they are a physical embodiment of billions of years of unconscious
generational learning, for the painstaking trial and error of evolution.
(10:42):
But at their simplest level, genes are pieces of DNA that make the little machines called
proteins that make a plant possible.
And in this episode, we'll explore just a few examples of specific genes and the proteins
they produce and will draw an example of proteins that are central to plant growth and development.
I'll be summarizing the products of research that now spans more than a century, connecting
(11:04):
up plant physiology to genetics and hopefully by the end it will be clear why genes are
an ideal target for anyone who wants to make new crop varieties.
Welcome to Modified.
I'm your host Dr. Orlando D'Alange, Explancientist and Current Science teacher.
This podcast is my attempt to guide you through the science of GMOs and hopefully just enough
(11:26):
of the history and the social context to give you a passport in your own thinking.
And if all else fails, I hope you'll enjoy some of the surprising stories and fascinating
facts in the world of genetically modified plants.
This is episode 4, How Genes Make Plants.
If you're tuning in for the first time, I recommend heading back to episode 1 and starting
there.
(11:46):
Otherwise, let's proceed.
Industry for Japan, Agriculture for Taiwan.
So went an official imperial slogan in the 1920s.
This was already decades into the occupational rule of Taiwan by Japan after a military
conquest at the end of the 19th century.
(12:06):
The Japanese imperial government was determined to show how successfully they could operate
Taiwan as a colony.
That meant, among other things, investing an agricultural research to turn Taiwan into
the bread basket of the Japanese Empire.
So it is perhaps no surprise that one of the greatest discoveries of agricultural science
was made in Taiwan by a Japanese scientist in the 1920s.
(12:29):
That is the discovery of gibberalans.
If you are not an agricultural or plant scientist, I think it's unlikely that you'll have heard
of gibberalans, and yet they are at the heart of one of the most dramatic episodes of
the 20th century, the Green Revolution.
Depending on who you ask, the Green Revolution could be described as one of the greatest
(12:49):
humanitarian projects of all time, or a colonial plot to destroy the economies and
culture developing countries.
The Green Revolution was a decades-long concerted push to breed new, higher yield varieties
of staple crops, starting with wheat in Mexico and a project led by an American scientist,
Norman Borlaug.
(13:11):
His work involved applying advances in genetics and plant science with one of the key methods
being to find mutations in genes related to gibberalans.
The Green Revolution did boost yields of staple crops, in that process it also exported
American approaches to agricultural production around the world.
We'll learn more about the Green Revolution in a later episode, but for now let's get
(13:32):
back to early 20th century Taiwan.
Researchers using cutting edge techniques in plant physiology and genetics were hard at
work to adapt Japanese or high varieties to the tropical climate of Taiwan, as well
as researching the various diseases and ailments encountered that were limiting yields.
Among those Japanese researchers studying rice and Taipei was a Ichi-Kurasawa.
(13:56):
Like many other researchers, he studied the diseases that afflicted rice varieties in
this tropical climate of Taiwan.
Dr. Kurosawa had taken an interest in a specific disease called foolish seedling disease in
English.
Rice plants with this disease grew very tall, very quickly, and then would bend over on
rot in the mud because they had very weak stems.
(14:17):
From studying samples carefully under a microscope, he established the diseases caused by a fungus,
Jibarilla Fujikuroi.
But how?
Following an experimental design approach going back to Libby Pastur, he took some of
the fungus, grounded up, and then sterilized it so that he could be sure that none of
the fungus cells were alive and active, but that the chemicals they produced would still
(14:39):
be present in the extract.
Basically he made sterile fungus soup.
No living cells, but all the biochemicals would still be in the soup.
And then he applied this fungus soup to rice seedlings.
To his satisfaction, they grew very tall, very quickly, and had very weak stems.
He showed that there was some chemical that the fungus made that had this effect on the
(15:03):
plants.
And he named it "jibarilla" after the fungus, Jibarilla.
The discovery was not put in a drawer and forgotten.
With the excited agricultural scientists across Japan, and by the end of the 1930s, the chemical
had been purified in its molecular composition studied, and the interest was not limited
to the Japanese Empire.
Science had been an interconnected global field since the mid-19th century, facilitated
(15:27):
by improvements in communication technology.
And so, before long, researchers in Europe and United States were also researching these
fascinating compounds.
Marguerat Radley, a British agricultural scientist working in the UK in the 1950s, was the first
to report what had been suspected, but not proven to them.
The Jibarillans are naturally produced by plants themselves.
(15:50):
She did this using a similar approach to a chikourousau, a decades previously.
She prepared an extract from normal beam plants, and applied them to short beam plants from
a variety that were consistently much shorter than normal.
She found that this allowed the plants from the short variety to grow to a normal height.
Essentially, she showed that the dwarf beams were missing some chemical produced in wild-type
(16:11):
beams.
Studying further, found that this was indeed the Jibarillans, the same chemical structure,
produced by the fungus discovered about 20 years earlier.
The fungus was just hijacking an existing system that plants used to regulate their own growth,
controlling the production of the amounts of Jibarillans produced in plants to promote
or reduce growth rates.
(16:33):
Specifically, what Jibarillans promote is cell expansion.
The meristems we met at the beginning of the episodes are sites of cell division.
However, even though the meristemal has followed thousands of cells, the cells and the meristem
are tiny.
Generally, the whole organ is only visible as a tiny bump on the side of the stem or root.
Apply some Jibarillan, and those cells will expand dramatically, and the new branch,
(16:55):
root leaf or flower, will begin to grow in form over a period of days.
The discovery that Jibarillans are produced in side plants themselves wasn't totally
surprising in itself.
It was already known that another group of chemicals, orksins, could have dramatic effects
on plant growth and physiology.
In fact, Charles Darwin, a evolution fame, carried out important early research in orksins.
(17:17):
Orksins accumulate in the meristems and are the signal to be a meristem and continue
to be a meristem.
Remember that the meristem is that cluster of continually dividing cells that can
be a site for new tissue and organ formation.
With Jibarillans added to the mix, it was clear that there are multiple different signals
called plant hormones that behave like master regulators of plant growth and physiology.
(17:40):
First, orksins and Jibarillans, and then as the 20th century war on, more and more were
discovered, cytokinins, abcyzic acid, ethylene, brusinosteroid, cilic acid and more.
They all have a unique set of effects, though there is some overlap between them.
Cylicinins encourage cells to stop dividing and to differentiate into a specific organ
type.
(18:01):
Ethylene causes fruit to ripen, which is a complex set of changes to cell structure and
biochemistry that have to be coordinated to all occur at the same time.
Cylic acid triggers a whole suite of changes that allow the plant to better resist pathogenic
microbes, things like churning out toxic compounds to kill the microbes.
(18:22):
There are about 10 major groups of plant hormone depending on how you define them.
Plant hormones are themselves just one subset of the much larger suite of signaling molecules,
chemicals that transmit a signal, a piece of information.
All cells and all organisms rely on signaling molecules of some kind.
That signal can then be interpreted in the same cell, or in the case of a plant the signaling
(18:44):
molecule can also get moved through the plant in the xylomorphic system, or get released
as gases from the leaves, to be absorbed by nearby leaves on the same or neighboring plants.
Churning molecules are how different cells in the same plant talk to each other, and how
neighboring plants or even organisms from different species can talk to each other.
(19:04):
Plant hormones are small organic molecules.
The atoms in a plant hormone do still form quite complex structures, with oxygen and hydrogen
atoms as well as some other elements like nitrogen, and of course carbon.
But they are small and they are made of 10 to 100 carbon atoms linked into a molecule,
as opposed to the tens of thousands of carbon atoms that might be in a single protein.
(19:27):
Proteins like DNA remember are polymers.
And with polymers as our hook, let's recap quickly on DNA proteins and genes.
Pretty important stuff is worth going back over.
DNA is a polymer made of units called bases.
Proteins are polymers made of units called amino acids.
There are four different types of bases that are all similar to each other, with subtle
(19:49):
but important differences.
And without those differences, you wouldn't be able to have information encoded in DNA,
through the precise order of the bases, A, G, C, and T, along the DNA polymer.
The 20 different amino acid types that make up proteins have a common core unit and then
dramatically different side chains, meaning the variable section of the amino acid that
(20:11):
literally sticks out of the side of the chain of amino acids.
In proteins, these amino acid differences are crucial.
The other magic ingredient that lets proteins do what they do.
The different side chains of amino acids have different physical structures, allowing
them to interact in different ways of other molecules, and they have different chemical
and electrostatic properties, allowing them to facilitate different kinds of chemical reactions.
(20:36):
The different properties of each amino acid type, not only change how that specific amino
acid within the larger protein can interact with other molecules, but they crucially affect
how all the amino acids within a single protein chain interact with each other.
Some amino acids attract each other, some repel each other, that mixture of attraction and
repulsion causes the chain to fold up into complex 3D shapes.
(21:00):
And then very often, multiple amino acid chains will actually come together to form a stable
mega structure.
An individual amino acid chain in living cell could have anywhere from 10 amino acids to tens
of thousands of amino acids.
Still, that pales in comparison to the hundreds of millions of DNA bases in a typical chromosome,
which if you remember, those are the things that we have a bunch of in each of ourselves,
(21:23):
and each one is a single mass of DNA chain.
A typical protein is a chain over a few hundred amino acids.
So how does that relate to the hundreds of millions of DNA bases in a chromosome?
What's the connection between them?
Each chromosome is a giant unbroken DNA chain, like I mentioned, but it contains thousands
(21:45):
of separate overlapping units that are what we call genes.
And each of these genes is much shorter.
A gene has a few functional sections to it, one region at the physical beginning of the
gene, called the promoter, that recruits them a molecular machinery necessary to make
the RNA copy that then gets fed into a ribosome to churn out a protein.
(22:05):
Then the middle of the gene is the coding sequence.
This is the bit that encodes the protein.
This works via a free to one code, the radianae bases per amino acid, which is necessary because
there are only four different DNA bases, but 20 amino acids.
And then there is the terminator, which has signals that stop the RNA production process.
(22:25):
Basically, the gene is a set of DNA bases that encode a single protein, plus other DNA,
either side that has important signals read by that machinery that turns DNA into RNA.
That machinery is actually a set of dedicated proteins.
The process of turning DNA into RNA is called transcription, and so the proteins involved
(22:45):
are called transcription factors.
So let's connect this back to Giberolins.
Those are small organic molecules, which are not proteins.
So how do they get made?
Are they also encoded by genes?
Yes and no.
But the 1930s, when Giberolins were being categorized, it was already well established
that a lot of biochemistry inside cells is facilitated by things called enzymes, and the enzymes
(23:10):
are proteins, made of the same basic amino acid building blocks as structural proteins in
fingernails and muscle fibers.
Unlike those structural proteins, the proteins that we call enzymes have complex folded shapes
that often have a physical pocket that has just the right space and configuration for
one or multiple molecules to make contact.
And then within the pocket, one or a few specific amino acids will facilitate a chemical
(23:34):
reaction that either makes a new chemical bond or breaks one.
The details change a lot, but that's the basics of how an enzyme works.
Without them, there would be no life on Earth.
Because life on Earth relies essentially on chemical reactions that would never happen
if you just let all the molecules involved float around interacting randomly.
Inzams allow structure and direction to exist within networks of chemical reactions,
(23:57):
rather than chaos and a constant back and forth of making and unmaking.
So even those cells are full of diversity of molecules, not just DNA and proteins.
They all indirectly connect back.
Proteins, specifically the subset we call enzymes, direct the biochemical reactions of
the cell, and those proteins are all manufactured in the cell according to the blueprints encoded
(24:19):
in DNA in functional subunits we call genes.
So where did we get to so far?
We know that there are things called chibarellins, they are small molecules that are made by
plants and they signal to cells that they should grow and expand.
Like all small molecules in the cell, their synthesis must be controlled by enzymes.
(24:40):
All of that was clear by the late 1950s.
Decades of plant genetics research had yielded plenty of mutant varieties that were short
to the normal, which made it simple to start testing whether the mutated genes had something
to do with chibarellins.
That was exactly what Bernard Finney did.
He was an American plant scientist working at UCLA in the 1950s.
(25:03):
He started taking mutants, for example, dwarf mutants of maize.
That's the name for corn used by plant scientists because in other English-speaking countries, the
word corn is used for wheat.
Anyway, he found that in many of those dwarf maize mutants purified chibarellins would cause
them to grow to normal height, similar to what Margaret Radley first demonstrated a few years
earlier.
(25:24):
At this time, with purified chibarellins, he could be sure that it was those exact molecules
that were responsible for the effect.
And by carefully studying the behavior of the different mutants and response to carefully
externally apply chibarellins, Finney was able to start piecing together a story about
how chibarellins work in plants.
Over the coming decades, his lab and others show that there were a whole range of genes
(25:46):
involved, each one encoding a different protein.
Some of these genes encode the enzymes that actually synthesize chibarellins.
If those are broken or mutated, the plant will not be able to make its own chibarellins
and will be short, but it will respond perfectly well if the chibarellins are applied externally.
(26:06):
Other genes encode the proteins that detect chibarellins in the cell, similar to enzymes,
proteins like this called signaling proteins often have pockets to capture small molecules.
And then binding of the small molecule will trigger some change in the protein, for instance,
shifting the structure to allow the protein to move from the main area of the cell, the cytoplasm,
(26:28):
into the nucleus where the DNA is.
Inside the nucleus, there will be a weighting transcription factor, remember them?
The transcription factor will bind to the signaling protein, and together that will trigger
some change in the transcription factor in its function that will allow it to turn some
target genes on or off up or down.
AKA, the hormone will trigger changes in gene expression.
(26:51):
And if any of those genes, the genes that encode the signaling proteins or the transcription
factor, if they are broken, then the plant will not be able to respond at least fully
to externally apply chibarellins no matter what.
And then there are the genes that are turned on or off up or down by the transcription
(27:12):
factor, the target genes themselves that produce the observable response in the plants, growth
and physiology.
For chibarellins, a lot of these encode cell wall modifying enzymes.
You are probably aware that plant cells, unlike our own cells, have rigid walls, which give
them shape and physical strength.
These cell walls can be relatively thin, or they can be very thick and embedded with strengthening
(27:35):
molecules like lignin, which is the main constituent of wood.
One cell walls can be very diverse from cell to cell and plant to plant, and crucially
they are dynamic.
They can be made and unmade, strengthened and weakened.
And if a cell is to expand to get bigger, then they can be loosened to allow this, and
they're made more rigid again at some point, like loosening a belt and then refarsening it.
(27:59):
The main structural components of the cell wall are not proteins.
They are sugar-based polymers, cellulose, as well as the aforementioned lignin, but
it is proteins that control the production of these polymers.
Proteins help to ferry all the building materials from inside the cell to the outside where
the wall is.
The wall sits just on the outside of the cell with lots of cross-links keeping it attached
(28:21):
to the cell.
Chibarellins master response regulator proteins, those transcription factors that get activated
by chibarellins.
When they are activated, they turn on genes that encode cell wall remodeling enzymes
that can loosen the belt of the cell wall, allowing the plant cell to grow.
It is not the only thing that chibarellins do, but is one important part.
(28:41):
And so you can imagine if those target genes, such as the cell wall remodifying enzymes
are broken, then you'll see that some part of the chibarellin response is completely
lacking.
You might find that when you apply chibarellin, there is some element of the normal response,
but not the whole response.
Hopefully, if you weren't already, you are now convinced that no matter how a plant may
(29:05):
look at times.
They are at an amic hive of biochemical activity, with genes and proteins driving it all forward.
And the plant scientists have been picking this all apart in detail for about a century,
and in the process, finding ways to turn the molecular levers and hijack the biochemical
pathways to meet human ends.
Developing crop plants that will, depending on your perspective, feed hungry people and
(29:30):
create a tasty bounty of produce or subvert traditional food systems to further the interests
of imperialists and capitalists.
Well done for making it through, what has been an episode of Dense with Information.
In our next episode, we'll pick up by looking at some of the genes involved in defending
plants against microbes, recapping and reinforcing some of the key concepts and facts that we've
(29:53):
covered in this episode.
Since this one has been so dense with facts, I think a little recap of take-home messages
will be helpful for everyone.
Number one, plant development is indeterminate.
It doesn't follow a predetermined master plan that says how many roots leaves or flowers
the adult plant will have.
Instead, merry stems are sites of new organ formation that are present within the embryo
(30:16):
and are retained through the life of the plant.
With additional meristems forming as the plant grows to allow for side branches and side
roots.
Information, number two, information about the environment and about the states of the
cell are processed and transformed into changes in gene expression.
This is common to all cells, not just plant cells.
(30:36):
Number three, plant hormones are master regulators of growth and physiology.
Examples include auctions and gibberalans.
Number four, proteins are chains of amino acids.
Immuno acid diversity allows for proteins to have a huge possible range of structures and
functions.
Number five, we can group proteins based on their functions.
(30:58):
For instance, enzymes facilitate biochemical reactions, including the synthesis of plant
hormones.
Other proteins regulate gene expression and we call them transcription factors.
Thank you for listening to Modified.
This was episode four, How genes make plants.
It was written by me or landed a launch.
I used many sources to help me research this episode.
(31:20):
If you're interested in learning more about the history of Japanese colonial agricultural
research in Taiwan and the context of global colonial history, then check out the 2020 article
Hurai Rice in the Making of Japanese Colonial Taiwan by Waily Liu, linked in the show notes.
This is a tiny one person podcast, so please please if you're enjoying it, subscribe, leave
(31:41):
a review and tell a friend.
If you have notes, well I'd love to hear them and you can email me, Orlando at ModifiedPod.com
and I'd love to hear from you.
I'm actually planning to add an extra episode in a couple of weeks, just devoted to answering
listener questions.
From episode six, we'll shift years to talking more specifically about crop plants and agricultural
(32:02):
science.
But before then, between episodes five and six, I'll be doing a special episode answering
your questions.
To send me in your questions about genetics and plant science generally, and I'll pick
a few to dive into in detail in a special episode.
So that's your questions on genetics or plant science, email to Orlando@modifiedpod.com
(32:24):
as always you can find out more about me and the podcast at the website, ModifiedPod.com.
That's M-O-D-I-E-D-P-O-D-O-W-W-D.
Thanks for listening, until next time, bye!
( considerate music )
Question.
(00:03):
How do you like to eat a peanut?
Before I go further, big apology to all those out there with peanut allergies.
I am truly very sorry because I love peanuts and so do most of the planet as far as I can
tell.
Optimus and Elenia of being enjoyed in South America, peanuts got the colonial treatment
and were very rapidly spread around their whole world and enjoyed everywhere.
(00:23):
The colonial connections are particularly strong in that it was enslaved Africans who
brought the peanuts to the United States.
Ask Americans today who they associate with peanuts and you'll probably get either
late President Jimmy Carter who was a peanut farmer before launching his political career
or you'll get George Washington Carver who does have a very strong claim to peanut fame
(00:44):
but country but topopular belief did not invent peanut butter.
In fact Carver was an agronomist, part of the very 20th century American project used
scientific principles to improve agriculture generally by boosting productivity with automation,
fertilization and irrigation.
Carver himself was more focused on techniques that could improve soils, particularly crop
(01:06):
rotation and in supporting black farmers to improve profits by growing crops such as peanuts
they can maybe process in a variety of ways to add value and he pursued his applied research
in community education from his position as head of agriculture at Tuskegee University
in Alabama for the first few decades of the 20th century.
Anyway, back to peanuts and eating them.
(01:29):
Maybe like me you get a little kick out of taking the peanut, sliding your nails around
until you find the place where the two halves meet and then sliding your nail into the
tiny slit as you definitely pull it apart.
Inside, tucked between the two halves is a little nodule.
It doesn't look like much just a little lump of peanut colored material.
(01:50):
If I'm eating peanuts it's likely they're roasted and salted which means they're dead.
But if you had raw peanuts you're dealing with something else, not a dead thing but a living
breathing thing, a seed that is not just full of potential life but is currently alive.
While it's just a seed at this point it's not doing anything too exciting it has very
low moisture content and the breathing already we should say molecular respiration is happening
(02:15):
at a very low rate.
A living peanut is not photosynthesizing meaning it doesn't have any green leaves to harvest
sunlight with.
But it is at a very low rate using chemical reactions to break apart sugars to produce
energy to power a baseline level of cellular processes including gene expression.
And if you were to take that peanut and put it in some damp soil with some overhead light
(02:39):
those dormant biological processes will very quickly ramp up within a few hours and then
within a few days all that hard molecular work will be easily visible to the naked eye.
The changes begin like I mentioned long before you can see them and well within a day.
The seed begins to swell and the cells and the seed coat that's the thin brown wrapping
(02:59):
around the peanut soften begin to fall away.
Not so much fall away is get ripped apart as something begins to stir from within the
peanut.
A tiny little nodule that looks like nothing very much begins to swell and grow.
A tiny protrusion just a millimeter long in the dry nut forces its way downward into
(03:21):
the soil expanding to ten times its original size over the space of a day.
This is the radical spell RADICLE.
The original root already preformed and hidden inside the embryo at the center of the
seed and at the same time as the radical is pushing downwards those two huge halves of
the peanut that surround it are undergoing some dramatic changes.
(03:45):
They're pushing outwards separating the soil around the embryo and turning light green.
Because you see what I've been calling the halves of the peanut are the cotterledans.
Often called seed leaves and yes the main body of what we consider a peanut is a set of dormant
seed leaves.
These are different from standard peanut leaves of a peanut plant and they play a specific
(04:09):
role in germination that's the process of the seed transforming into a plant.
In many plants the cotterledans push upwards after the soil and spread out to form fully
functional leaves the first leaves of the emerging plant.
But for peanuts like most plants with large seeds the cotterledans remain below ground, mostly
(04:29):
serving as a store of nutrition for the radical pushing down into the earth and for the
final crucial part of the embryo the plumeul.
The plumeul is inside the little nodule between the cotterledans just where the radical was
and it's a set of a few tiny true leaves and a stem that pushed their way up into the
light and at the top of the stem is the engine of plant growth to come the shoot apical
(04:55):
meristem.
The seed of a plant is similar to an animal embryo it has a bunch of parts in miniature
that grow but unlike an animal embryo there is no blueprint for what the final adult version
will look like.
Animals can develop totally new organs during development that is true that are not in the
original embryo but that will all happen according to a specific predetermined plan encoded in
(05:19):
the genes of the embryo cells.
A plant doesn't develop according to a predetermined plan in the same way.
We say that they have indeterminate development, they have a kit of parts leaves roots branches
flowers and the exact number size and relationship between all these will develop in response
to the environment and can continue to change over the whole lifetime lifespan of the plants.
(05:44):
Well that does differ a bit from plant to plant some oversimplifying a little.
Some plants do tend to reach a particular end size before reproducing and dying but still
there will be lots of variation in how they get to that end point the exact number and
arrangement of organs they produce along the way.
And facilitating that indeterminate dynamic development are a special pair of organs the
(06:05):
shoot apical meristem above and root apical meristem below.
These organs are patches of dynamic dividing cells and not just dividing but differentiating
as they do so.
The meristem always remains through the life of the plant always as a sensor of dividing
cells being carried higher and higher or deeper and deeper down as it leaves behind it a trail
(06:27):
of differentiated plant organs.
We animals don't have this sort of developmental dynamism.
We do have some pools of constantly dividing and differentiating cells.
In humans the most obvious example is that for our whole lives we have pockets of what are
called stem cells in our bone marrow, constantly dividing with the daughter cells they produce
differentiating into all the different types of blood cells.
(06:51):
How can one stem cell in our bone marrow produce all the different types of blood cells?
And how can the apical meristem cells in a grown plant produce every possible organ of the
adult plant?
It's possible because every cell in an organism contains the whole genome.
So within each cell is the full complement of genes accessible within the nucleus to an
army of proteins that can process information from the outside and use that information
(07:15):
to select the most advantageous genes to turn on and off and in doing so trigger a few
of the cells from the meristem to form a new branch here or a new root there or if the timing
is perfect to produce a flower.
Inside the meristem cells the genes are very busy indeed.
The nucleus is thrombing with life, the DNA is feld and unfurled, proteins called transcription
(07:38):
factors are searching along the DNA without hands, without eyes, but guided by the laws of
thermodynamics till they find the right DNA sequence.
Once they found the right DNA sequence they stop moving around and stay in place long enough
to recruit the master of ceremonies RNA polymerase.
That's the mega protein complex that runs along the DNA, scanning it and using it to create
(08:00):
messenger copies of the sequence made of RNA, the nimble sister of DNA.
RNA can leave the nucleus and head off into the cytoplasm of the cell, waiting in the cytoplasm
is another type of mega complex, the ribosome.
In order to make sure the protein is specialized RNA molecules the ribosome has a cavity
in the side that accepts the messenger RNA molecule freshly arrived from the nucleus.
(08:24):
The messenger RNA is fed through the ribosome with the codenance RNA red to produce a protein
with a specific amino acid sequence.
When we talk about genetic code being read in a cell this is really what we mean.
The RNA polymerase creates an RNA version of the gene and the ribosome reads the RNA version
of the original DNA code without a brain it understands the message overseeing the assembly
(08:49):
of a new protein molecule following the precise instructions that lay within the RNA molecule
which come directly from the original DNA master copy.
Once the ribosome has done its thing the new protein molecule is ready to begin its life.
It may live for just a few minutes or it may live for years.
It may be a piece of a fibosel that will form the internal structure for the cell.
(09:11):
It may be one of the hundreds of proteins that facilitate the harvesting of sunlight to
produce energy.
It may be an aquaporin, a type of protein that sits in the cell membrane, the fatty barrier
that separates the inside from the outside of the cell.
Given the right cues it lets water rush in forcing the cell to expand, a crucial part
of all the growth processes we've described.
(09:33):
It could itself be a transcription factor destined to head back into the nucleus to join
the dance of DNA, firling and unfirling, scanning and reading.
None of this could happen outside the context or the environment the seed finds itself in,
the water, the sunlight, the minerals in the soil, the bacteria and fungi that surround
(09:54):
the seed.
In the case of our thought experiment, you the human who placed it in the soil are a
crucial environmental factor.
These environmental factors are actively sensed and responded to by the cells in the growing
plant with corresponding changes in gene expression.
In a sense the genes are the locus of information processing, with all this complex information
(10:17):
about the external environment, the internal condition and position of the cell all processed
into changes to the expression of the several thousand genes in the nucleus.
Genes are a physical scaffold within the cell, on which information processing can happen.
They allow for computation, they are a physical embodiment of billions of years of unconscious
generational learning, for the painstaking trial and error of evolution.
(10:42):
But at their simplest level, genes are pieces of DNA that make the little machines called
proteins that make a plant possible.
And in this episode, we'll explore just a few examples of specific genes and the proteins
they produce and will draw an example of proteins that are central to plant growth and development.
I'll be summarizing the products of research that now spans more than a century, connecting
(11:04):
up plant physiology to genetics and hopefully by the end it will be clear why genes are
an ideal target for anyone who wants to make new crop varieties.
Welcome to Modified.
I'm your host Dr. Orlando D'Alange, Explancientist and Current Science teacher.
This podcast is my attempt to guide you through the science of GMOs and hopefully just enough
(11:26):
of the history and the social context to give you a passport in your own thinking.
And if all else fails, I hope you'll enjoy some of the surprising stories and fascinating
facts in the world of genetically modified plants.
This is episode 4, How Genes Make Plants.
If you're tuning in for the first time, I recommend heading back to episode 1 and starting
there.
(11:46):
Otherwise, let's proceed.
Industry for Japan, Agriculture for Taiwan.
So went an official imperial slogan in the 1920s.
This was already decades into the occupational rule of Taiwan by Japan after a military
conquest at the end of the 19th century.
(12:06):
The Japanese imperial government was determined to show how successfully they could operate
Taiwan as a colony.
That meant, among other things, investing an agricultural research to turn Taiwan into
the bread basket of the Japanese Empire.
So it is perhaps no surprise that one of the greatest discoveries of agricultural science
was made in Taiwan by a Japanese scientist in the 1920s.
(12:29):
That is the discovery of gibberalans.
If you are not an agricultural or plant scientist, I think it's unlikely that you'll have heard
of gibberalans, and yet they are at the heart of one of the most dramatic episodes of
the 20th century, the Green Revolution.
Depending on who you ask, the Green Revolution could be described as one of the greatest
(12:49):
humanitarian projects of all time, or a colonial plot to destroy the economies and
culture developing countries.
The Green Revolution was a decades-long concerted push to breed new, higher yield varieties
of staple crops, starting with wheat in Mexico and a project led by an American scientist,
Norman Borlaug.
(13:11):
His work involved applying advances in genetics and plant science with one of the key methods
being to find mutations in genes related to gibberalans.
The Green Revolution did boost yields of staple crops, in that process it also exported
American approaches to agricultural production around the world.
We'll learn more about the Green Revolution in a later episode, but for now let's get
(13:32):
back to early 20th century Taiwan.
Researchers using cutting edge techniques in plant physiology and genetics were hard at
work to adapt Japanese or high varieties to the tropical climate of Taiwan, as well
as researching the various diseases and ailments encountered that were limiting yields.
Among those Japanese researchers studying rice and Taipei was a Ichi-Kurasawa.
(13:56):
Like many other researchers, he studied the diseases that afflicted rice varieties in
this tropical climate of Taiwan.
Dr. Kurosawa had taken an interest in a specific disease called foolish seedling disease in
English.
Rice plants with this disease grew very tall, very quickly, and then would bend over on
rot in the mud because they had very weak stems.
(14:17):
From studying samples carefully under a microscope, he established the diseases caused by a fungus,
Jibarilla Fujikuroi.
But how?
Following an experimental design approach going back to Libby Pastur, he took some of
the fungus, grounded up, and then sterilized it so that he could be sure that none of
the fungus cells were alive and active, but that the chemicals they produced would still
(14:39):
be present in the extract.
Basically he made sterile fungus soup.
No living cells, but all the biochemicals would still be in the soup.
And then he applied this fungus soup to rice seedlings.
To his satisfaction, they grew very tall, very quickly, and had very weak stems.
He showed that there was some chemical that the fungus made that had this effect on the
(15:03):
plants.
And he named it "jibarilla" after the fungus, Jibarilla.
The discovery was not put in a drawer and forgotten.
With the excited agricultural scientists across Japan, and by the end of the 1930s, the chemical
had been purified in its molecular composition studied, and the interest was not limited
to the Japanese Empire.
Science had been an interconnected global field since the mid-19th century, facilitated
(15:27):
by improvements in communication technology.
And so, before long, researchers in Europe and United States were also researching these
fascinating compounds.
Marguerat Radley, a British agricultural scientist working in the UK in the 1950s, was the first
to report what had been suspected, but not proven to them.
The Jibarillans are naturally produced by plants themselves.
(15:50):
She did this using a similar approach to a chikourousau, a decades previously.
She prepared an extract from normal beam plants, and applied them to short beam plants from
a variety that were consistently much shorter than normal.
She found that this allowed the plants from the short variety to grow to a normal height.
Essentially, she showed that the dwarf beams were missing some chemical produced in wild-type
(16:11):
beams.
Studying further, found that this was indeed the Jibarillans, the same chemical structure,
produced by the fungus discovered about 20 years earlier.
The fungus was just hijacking an existing system that plants used to regulate their own growth,
controlling the production of the amounts of Jibarillans produced in plants to promote
or reduce growth rates.
(16:33):
Specifically, what Jibarillans promote is cell expansion.
The meristems we met at the beginning of the episodes are sites of cell division.
However, even though the meristemal has followed thousands of cells, the cells and the meristem
are tiny.
Generally, the whole organ is only visible as a tiny bump on the side of the stem or root.
Apply some Jibarillan, and those cells will expand dramatically, and the new branch,
(16:55):
root leaf or flower, will begin to grow in form over a period of days.
The discovery that Jibarillans are produced in side plants themselves wasn't totally
surprising in itself.
It was already known that another group of chemicals, orksins, could have dramatic effects
on plant growth and physiology.
In fact, Charles Darwin, a evolution fame, carried out important early research in orksins.
(17:17):
Orksins accumulate in the meristems and are the signal to be a meristem and continue
to be a meristem.
Remember that the meristem is that cluster of continually dividing cells that can
be a site for new tissue and organ formation.
With Jibarillans added to the mix, it was clear that there are multiple different signals
called plant hormones that behave like master regulators of plant growth and physiology.
(17:40):
First, orksins and Jibarillans, and then as the 20th century war on, more and more were
discovered, cytokinins, abcyzic acid, ethylene, brusinosteroid, cilic acid and more.
They all have a unique set of effects, though there is some overlap between them.
Cylicinins encourage cells to stop dividing and to differentiate into a specific organ
type.
(18:01):
Ethylene causes fruit to ripen, which is a complex set of changes to cell structure and
biochemistry that have to be coordinated to all occur at the same time.
Cylic acid triggers a whole suite of changes that allow the plant to better resist pathogenic
microbes, things like churning out toxic compounds to kill the microbes.
(18:22):
There are about 10 major groups of plant hormone depending on how you define them.
Plant hormones are themselves just one subset of the much larger suite of signaling molecules,
chemicals that transmit a signal, a piece of information.
All cells and all organisms rely on signaling molecules of some kind.
That signal can then be interpreted in the same cell, or in the case of a plant the signaling
(18:44):
molecule can also get moved through the plant in the xylomorphic system, or get released
as gases from the leaves, to be absorbed by nearby leaves on the same or neighboring plants.
Churning molecules are how different cells in the same plant talk to each other, and how
neighboring plants or even organisms from different species can talk to each other.
(19:04):
Plant hormones are small organic molecules.
The atoms in a plant hormone do still form quite complex structures, with oxygen and hydrogen
atoms as well as some other elements like nitrogen, and of course carbon.
But they are small and they are made of 10 to 100 carbon atoms linked into a molecule,
as opposed to the tens of thousands of carbon atoms that might be in a single protein.
(19:27):
Proteins like DNA remember are polymers.
And with polymers as our hook, let's recap quickly on DNA proteins and genes.
Pretty important stuff is worth going back over.
DNA is a polymer made of units called bases.
Proteins are polymers made of units called amino acids.
There are four different types of bases that are all similar to each other, with subtle
(19:49):
but important differences.
And without those differences, you wouldn't be able to have information encoded in DNA,
through the precise order of the bases, A, G, C, and T, along the DNA polymer.
The 20 different amino acid types that make up proteins have a common core unit and then
dramatically different side chains, meaning the variable section of the amino acid that
(20:11):
literally sticks out of the side of the chain of amino acids.
In proteins, these amino acid differences are crucial.
The other magic ingredient that lets proteins do what they do.
The different side chains of amino acids have different physical structures, allowing
them to interact in different ways of other molecules, and they have different chemical
and electrostatic properties, allowing them to facilitate different kinds of chemical reactions.
(20:36):
The different properties of each amino acid type, not only change how that specific amino
acid within the larger protein can interact with other molecules, but they crucially affect
how all the amino acids within a single protein chain interact with each other.
Some amino acids attract each other, some repel each other, that mixture of attraction and
repulsion causes the chain to fold up into complex 3D shapes.
(21:00):
And then very often, multiple amino acid chains will actually come together to form a stable
mega structure.
An individual amino acid chain in living cell could have anywhere from 10 amino acids to tens
of thousands of amino acids.
Still, that pales in comparison to the hundreds of millions of DNA bases in a typical chromosome,
which if you remember, those are the things that we have a bunch of in each of ourselves,
(21:23):
and each one is a single mass of DNA chain.
A typical protein is a chain over a few hundred amino acids.
So how does that relate to the hundreds of millions of DNA bases in a chromosome?
What's the connection between them?
Each chromosome is a giant unbroken DNA chain, like I mentioned, but it contains thousands
(21:45):
of separate overlapping units that are what we call genes.
And each of these genes is much shorter.
A gene has a few functional sections to it, one region at the physical beginning of the
gene, called the promoter, that recruits them a molecular machinery necessary to make
the RNA copy that then gets fed into a ribosome to churn out a protein.
(22:05):
Then the middle of the gene is the coding sequence.
This is the bit that encodes the protein.
This works via a free to one code, the radianae bases per amino acid, which is necessary because
there are only four different DNA bases, but 20 amino acids.
And then there is the terminator, which has signals that stop the RNA production process.
(22:25):
Basically, the gene is a set of DNA bases that encode a single protein, plus other DNA,
either side that has important signals read by that machinery that turns DNA into RNA.
That machinery is actually a set of dedicated proteins.
The process of turning DNA into RNA is called transcription, and so the proteins involved
(22:45):
are called transcription factors.
So let's connect this back to Giberolins.
Those are small organic molecules, which are not proteins.
So how do they get made?
Are they also encoded by genes?
Yes and no.
But the 1930s, when Giberolins were being categorized, it was already well established
that a lot of biochemistry inside cells is facilitated by things called enzymes, and the enzymes
(23:10):
are proteins, made of the same basic amino acid building blocks as structural proteins in
fingernails and muscle fibers.
Unlike those structural proteins, the proteins that we call enzymes have complex folded shapes
that often have a physical pocket that has just the right space and configuration for
one or multiple molecules to make contact.
And then within the pocket, one or a few specific amino acids will facilitate a chemical
(23:34):
reaction that either makes a new chemical bond or breaks one.
The details change a lot, but that's the basics of how an enzyme works.
Without them, there would be no life on Earth.
Because life on Earth relies essentially on chemical reactions that would never happen
if you just let all the molecules involved float around interacting randomly.
Inzams allow structure and direction to exist within networks of chemical reactions,
(23:57):
rather than chaos and a constant back and forth of making and unmaking.
So even those cells are full of diversity of molecules, not just DNA and proteins.
They all indirectly connect back.
Proteins, specifically the subset we call enzymes, direct the biochemical reactions of
the cell, and those proteins are all manufactured in the cell according to the blueprints encoded
(24:19):
in DNA in functional subunits we call genes.
So where did we get to so far?
We know that there are things called chibarellins, they are small molecules that are made by
plants and they signal to cells that they should grow and expand.
Like all small molecules in the cell, their synthesis must be controlled by enzymes.
(24:40):
All of that was clear by the late 1950s.
Decades of plant genetics research had yielded plenty of mutant varieties that were short
to the normal, which made it simple to start testing whether the mutated genes had something
to do with chibarellins.
That was exactly what Bernard Finney did.
He was an American plant scientist working at UCLA in the 1950s.
(25:03):
He started taking mutants, for example, dwarf mutants of maize.
That's the name for corn used by plant scientists because in other English-speaking countries, the
word corn is used for wheat.
Anyway, he found that in many of those dwarf maize mutants purified chibarellins would cause
them to grow to normal height, similar to what Margaret Radley first demonstrated a few years
earlier.
(25:24):
At this time, with purified chibarellins, he could be sure that it was those exact molecules
that were responsible for the effect.
And by carefully studying the behavior of the different mutants and response to carefully
externally apply chibarellins, Finney was able to start piecing together a story about
how chibarellins work in plants.
Over the coming decades, his lab and others show that there were a whole range of genes
(25:46):
involved, each one encoding a different protein.
Some of these genes encode the enzymes that actually synthesize chibarellins.
If those are broken or mutated, the plant will not be able to make its own chibarellins
and will be short, but it will respond perfectly well if the chibarellins are applied externally.
(26:06):
Other genes encode the proteins that detect chibarellins in the cell, similar to enzymes,
proteins like this called signaling proteins often have pockets to capture small molecules.
And then binding of the small molecule will trigger some change in the protein, for instance,
shifting the structure to allow the protein to move from the main area of the cell, the cytoplasm,
(26:28):
into the nucleus where the DNA is.
Inside the nucleus, there will be a weighting transcription factor, remember them?
The transcription factor will bind to the signaling protein, and together that will trigger
some change in the transcription factor in its function that will allow it to turn some
target genes on or off up or down.
AKA, the hormone will trigger changes in gene expression.
(26:51):
And if any of those genes, the genes that encode the signaling proteins or the transcription
factor, if they are broken, then the plant will not be able to respond at least fully
to externally apply chibarellins no matter what.
And then there are the genes that are turned on or off up or down by the transcription
(27:12):
factor, the target genes themselves that produce the observable response in the plants, growth
and physiology.
For chibarellins, a lot of these encode cell wall modifying enzymes.
You are probably aware that plant cells, unlike our own cells, have rigid walls, which give
them shape and physical strength.
These cell walls can be relatively thin, or they can be very thick and embedded with strengthening
(27:35):
molecules like lignin, which is the main constituent of wood.
One cell walls can be very diverse from cell to cell and plant to plant, and crucially
they are dynamic.
They can be made and unmade, strengthened and weakened.
And if a cell is to expand to get bigger, then they can be loosened to allow this, and
they're made more rigid again at some point, like loosening a belt and then refarsening it.
(27:59):
The main structural components of the cell wall are not proteins.
They are sugar-based polymers, cellulose, as well as the aforementioned lignin, but
it is proteins that control the production of these polymers.
Proteins help to ferry all the building materials from inside the cell to the outside where
the wall is.
The wall sits just on the outside of the cell with lots of cross-links keeping it attached
(28:21):
to the cell.
Chibarellins master response regulator proteins, those transcription factors that get activated
by chibarellins.
When they are activated, they turn on genes that encode cell wall remodeling enzymes
that can loosen the belt of the cell wall, allowing the plant cell to grow.
It is not the only thing that chibarellins do, but is one important part.
(28:41):
And so you can imagine if those target genes, such as the cell wall remodifying enzymes
are broken, then you'll see that some part of the chibarellin response is completely
lacking.
You might find that when you apply chibarellin, there is some element of the normal response,
but not the whole response.
Hopefully, if you weren't already, you are now convinced that no matter how a plant may
(29:05):
look at times.
They are at an amic hive of biochemical activity, with genes and proteins driving it all forward.
And the plant scientists have been picking this all apart in detail for about a century,
and in the process, finding ways to turn the molecular levers and hijack the biochemical
pathways to meet human ends.
Developing crop plants that will, depending on your perspective, feed hungry people and
(29:30):
create a tasty bounty of produce or subvert traditional food systems to further the interests
of imperialists and capitalists.
Well done for making it through, what has been an episode of Dense with Information.
In our next episode, we'll pick up by looking at some of the genes involved in defending
plants against microbes, recapping and reinforcing some of the key concepts and facts that we've
(29:53):
covered in this episode.
Since this one has been so dense with facts, I think a little recap of take-home messages
will be helpful for everyone.
Number one, plant development is indeterminate.
It doesn't follow a predetermined master plan that says how many roots leaves or flowers
the adult plant will have.
Instead, merry stems are sites of new organ formation that are present within the embryo
(30:16):
and are retained through the life of the plant.
With additional meristems forming as the plant grows to allow for side branches and side
roots.
Information, number two, information about the environment and about the states of the
cell are processed and transformed into changes in gene expression.
This is common to all cells, not just plant cells.
(30:36):
Number three, plant hormones are master regulators of growth and physiology.
Examples include auctions and gibberalans.
Number four, proteins are chains of amino acids.
Immuno acid diversity allows for proteins to have a huge possible range of structures and
functions.
Number five, we can group proteins based on their functions.
(30:58):
For instance, enzymes facilitate biochemical reactions, including the synthesis of plant
hormones.
Other proteins regulate gene expression and we call them transcription factors.
Thank you for listening to Modified.
This was episode four, How genes make plants.
It was written by me or landed a launch.
I used many sources to help me research this episode.
(31:20):
If you're interested in learning more about the history of Japanese colonial agricultural
research in Taiwan and the context of global colonial history, then check out the 2020 article
Hurai Rice in the Making of Japanese Colonial Taiwan by Waily Liu, linked in the show notes.
This is a tiny one person podcast, so please please if you're enjoying it, subscribe, leave
(31:41):
a review and tell a friend.
If you have notes, well I'd love to hear them and you can email me, Orlando at ModifiedPod.com
and I'd love to hear from you.
I'm actually planning to add an extra episode in a couple of weeks, just devoted to answering
listener questions.
From episode six, we'll shift years to talking more specifically about crop plants and agricultural
(32:02):
science.
But before then, between episodes five and six, I'll be doing a special episode answering
your questions.
To send me in your questions about genetics and plant science generally, and I'll pick
a few to dive into in detail in a special episode.
So that's your questions on genetics or plant science, email to Orlando@modifiedpod.com
(32:24):
as always you can find out more about me and the podcast at the website, ModifiedPod.com.
That's M-O-D-I-E-D-P-O-D-O-W-W-D.
Thanks for listening, until next time, bye!
( considerate music )
Popular Podcasts
Las Culturistas with Matt Rogers and Bowen Yang
Ding dong! Join your culture consultants, Matt Rogers and Bowen Yang, on an unforgettable journey into the beating heart of CULTURE. Alongside sizzling special guests, they GET INTO the hottest pop-culture moments of the day and the formative cultural experiences that turned them into Culturistas. Produced by the Big Money Players Network and iHeartRadio.
Crime Junkie
Does hearing about a true crime case always leave you scouring the internet for the truth behind the story? Dive into your next mystery with Crime Junkie. Every Monday, join your host Ashley Flowers as she unravels all the details of infamous and underreported true crime cases with her best friend Brit Prawat. From cold cases to missing persons and heroes in our community who seek justice, Crime Junkie is your destination for theories and stories you won’t hear anywhere else. Whether you're a seasoned true crime enthusiast or new to the genre, you'll find yourself on the edge of your seat awaiting a new episode every Monday. If you can never get enough true crime... Congratulations, you’ve found your people. Follow to join a community of Crime Junkies! Crime Junkie is presented by audiochuck Media Company.
Stuff You Should Know
If you've ever wanted to know about champagne, satanism, the Stonewall Uprising, chaos theory, LSD, El Nino, true crime and Rosa Parks, then look no further. Josh and Chuck have you covered.