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[♪ INTRO]

Plants might seem kind of dull and boring,

but they are full of intrigue.

And two new papers published this week

showed just how manipulative and cunning

they can be.

The first, published in Nature Plants,

found that parasitic dodder plants from

the genus Cuscuta have stolen dozens of

genes from their hosts.

And they don't just take genes —

they use them too.

You see, dodders are parasitic plants

that don't have chlorophyll—the pigment

which captures light energy during photosynthesis.

That means they can't use light to fuel

chemical reactions in their cells.

So instead, they get pretty much everything

they need by getting real cozy with

a host plant.

They wrap around a plant's stems and

pierce them with structures called haustoria.

These create direct lines to the host's phloem

— the tube-like tissue that transports

nutrients down from the leaves to the

rest of the plant.

And nutrients and water aren't the only

thing dodders steal from their hosts.

Scientists identified 108 chunks of DNA

from other plants that field dodders have

added to their genomes.

These genes help the dodders grow better

haustoria, metabolize amino acids, and make

little pieces of RNA to send back into the

host to dull its defenses.

This isn't the first time scientists have

found evidence for horizontal gene transfer

in a parasitic plant, of course.

But the scale is noteworthy—these plants

have at least twice as many stolen genes

as any other genus of parasitic plant

studied to date.

Dodders might be better genetic thieves

because their haustoria latch on to stems,

where there are lots of young, healthy

cells full of DNA.

Other parasitic plants tend to attach to roots,

which have less DNA per unit of tissue.

Also, this genetic theft didn't happen

all at once.

16 to 20 of these genes were taken by a

dodder ancestor around 34 million years ago,

and have been evolving in two separate lineages

of dodders ever since.

Other stolen genes are much more recent, which

suggests this horizontal gene transfer is ongoing.

That flies in the face of conventional wisdom,

which is that gene transfer is rare in plants,

animals, fungi, and other living things with

complex, compartmented cells.

How these plants manage to pull off these

heists isn't yet clear.

They have to sneak past cell walls and

penetrate the protective membranes surrounding

their host cells' nuclei to get access to their genes.

And understanding how they do that could

teach us a lot about the inner workings

of cells and genomes.

But, however they do it, it's clear that

horizontal gene transfer is an unexpected

way parasitic plants can get a leg up on

their hosts over time.

And speaking of surprising plant abilities,

a paper published this week in the Proceedings

of the National Academy of Sciences suggests

some plants have an ingenious long-term

defense strategy against insects.

They can use chemicals and spikes to give

the pests leaky gut syndrome.

I'm really glad I don't have that.

That's where the lining of the intestine

is weakened and allows bits of food or

bacteria to leak into other layers of tissue.

When that happens, the unwelcome gunk can

trigger immune responses which sap the

animal's energy, leaving less for things

like growth and reproduction.

But the bacteria are the real danger —

if they get where they don't belong,

they can cause a life-threatening infection.

And the researchers found that's exactly

what happens to fall armyworms.

The defenses of the plants they eat leave them

vulnerable to infection from their own bacteria!

To figure this all out, the team raised fall

armyworm larvae in a sterile lab so they

didn't have any natural gut bacteria.

Then, they gave some of them food doused

with 1 of 3 bacteria species often found

in the animals' guts in the wild.

Other armyworms were fed sterile food

so they had no gut bacteria.

They then fed the larvae 1 of 3 kinds of maize.

One had long, spiky hairs on its surface

called trichomes.

Another produced a gut-piercing enzyme.

And the last had short, mostly harmless trichomes,

so it was considered the most palatable.

When the armyworms ate the spike -

or chemically - defended maizes, they suffered

— but it was their own bacteria that

made the biggest impact.

The armyworms with gut bacteria grew 60 to 76%

less than the ones without gut bacteria,

and up to 10x as many died, depending on

the maize they ate.

They also had greater immune response,

which likely explains the lack of growth.

And all of this varied by the specific

kind of bacteria in their gut.

That suggests a plant's defensive success

depends a lot on an insect's individual bacterial community.

Now, researchers want to better understand

these microbial communities, including how

they interact with plant defenses, because that

could help us win the war against agricultural pests.

It might allow researchers to design crops

that stack defenses on top of each other to

give insects leaky guts more effectively, for instance.

That way, they'd be able to thwart the bugs

that eat plants in a more targeted manner

while reducing the use of pesticides.

Even if, in the end, we can't really

implement this knowledge, simply discovering

that plants can induce this kind of syndrome

in insects reveals that their interactions

with animals are more complex than we used to think.

And all of this goes to show that while,

at times, the plant world may not seem as

dramatic as the animal world, plants are

every bit as conniving and ruthless.

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