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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 chlorophyllthe 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 noteworthythese 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.

  • Unfortunately people can be pretty conniving

  • and ruthless, as well, which is why it's so

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  • [♪ OUTRO]

This episode of SciShow News is

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この寄生植物は他の植物から100以上の遺伝子を盗んだ|SciShow News (This Parasitic Plant Stole Over 100 Genes From Other Plants | SciShow News)

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    林宜悉 に公開 2021 年 01 月 14 日
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