The genetic defenses of plants could be the key to crop protection, researchers say

Improving crops’ stress memory could make them more resilient to attack and reduce the need for harmful pesticides, a new study finds.

Plants have defense mechanisms that are triggered when attacked by pests or diseases, such as producing a bad-tasting chemical to scare off hungry caterpillars.

Scientists from the University of Sheffield have now discovered how plants build and store their immune response to such attacks – by coding a defense reaction in their DNA.

The effect can last for several weeks and in the same way strengthens the plant’s defenses during the next attack.

dr Jurriaan Ton, the study’s senior author, said his findings offer new ways to defend crops without resorting to toxic pesticides that can be catastrophic for insects beyond the target species.

The UK government recently approved the use of a neonicotinoid for use on sugar beet crops, although this class of chemicals was severely restricted in the EU and UK in 2013 for being deadly to bees and other key pollinators.

They said there was no other effective alternative to prevent an aphid-borne virus from destroying crops.

dr Ton said: “We rely on plants to feed the planet, but they’re essentially at the bottom of the food chain, they can’t move, so they’re incredibly vulnerable to attack from all sides, including insectivores and disease-causing pathogens.

“However, like animals, plants have evolved the ability to gain immunity after recovery from biotic stress, but they use different mechanisms to do so.”

Plants store their immune responses in junk DNA—so called because it doesn’t contain instructions on how to make proteins inside the cell.

dr Ton added: “The results of the study not only represent a major advance in our understanding of how plants remember the stress of previous attacks, but also reveal a new epigenetic function of a specific family of junk DNA.”

“This knowledge could help us to develop new breeding strategies and select plant varieties for food production that are primed to ward off pests and diseases.”

Thale cress treated with the hormone jasmonic acid (right) was more potent against caterpillars than without (left) (Handout/University of Sheffield/PA)

The study, published in Nature Plants, examined the long-term effects of the plant stress hormone jasmonic acid on thale cress, a relative of cabbage and mustard greens scientifically known as Arabidopsis thaliana.

When in contact with caterpillars, plants treated with jasmonic acid suffered less damage than those without.

The team discovered that the effects of jasmonic acid lasted for several weeks and were transferred to newly developed leaves, helping them resist being eaten by the caterpillars.

This acquired immunity is controlled in the plant’s genes. RNA molecules bind to a small protein, AG01. Together, they allow other genes tasked with defending the plant to respond faster and more powerfully to attacks.

The researchers hope this technique can be developed to protect plants with more complex genomes and are collaborating with an international plant breeding company to study its potential.

dr Samuel Wilkinson, first author of the paper, said: “As global food security is one of the greatest challenges we will face in the future, it is imperative that we find new ways to ensure the health and growth of the crops we rely on we are dependent .

“This research is the first step to complement and improve the effectiveness and durability of conventional plant breeding strategies by selecting plants with enhanced immune readiness as an alternative to the use of harmful pesticides.”

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