Hot Weather Weakens Plant Immune System, Study Finds

Uncertainty exists among scientists worldwide about why plants’ defenses against pathogens fade away under rising temperatures. However, the cure may lie in genetics.

Oct. 12, 2022
By Costas Vasilopoulos

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Scientists have long been try­ing to under­stand why plants become more vul­ner­a­ble to dis­ease when tem­per­a­tures rise.

While rel­e­vant research is ongo­ing, a group of researchers from uni­ver­si­ties around the world sought ways to restore the plants’ abil­ity to defend against pathogens in hot weather.

As cli­mate change accel­er­ates, we’re going to be under pres­sure to learn things in the lab and move them into the field faster. I can’t see how we’re going to do this with­out more accep­tance of genet­i­cally mod­i­fied plants.- Marc Nishimura, plant immu­nity researcher, Colorado State University

Plants get a lot more infec­tions at warm tem­per­a­tures because their level of basal immu­nity is down,” said Sheng-Yang He, a plant biol­o­gist at Duke University who led the research team. So we wanted to know, how do plants feel the heat? And can we actu­ally fix it to make plants heat-resilient?”

The study, pub­lished in Nature, focused on Arabidopsis thaliana, an unas­sum­ing weed widely known as the mouse-ear cress, con­sid­ered the lab rat of plants’ by plant biol­o­gists. Arabidopsis thaliana thrives on road­sides, open paths and vacant lots and is used in exper­i­ments world­wide due to its short life cycle and short and easy-to-mod­ify genome.

See Also:Studying Plant Reactions to Environmental Stressors Key to Sustainable Agriculture

The sci­en­tists said the main defense hor­mone of Arabidopsis thaliana is sal­i­cylic acid, which is used by many plants, includ­ing major crops, to resist dis­ease. However, the pro­duc­tion of sal­i­cylic acid can be dis­rupted when tem­per­a­tures rise a few degrees.

Extreme weather con­di­tions asso­ci­ated with cli­mate change affect many aspects of plant and ani­mal life, includ­ing the response to infec­tious dis­eases,” the researchers wrote. Production of sal­i­cylic acid, a cen­tral plant defense hor­mone, is par­tic­u­larly vul­ner­a­ble to sup­pres­sion by short peri­ods of hot weather above the nor­mal plant growth tem­per­a­ture range via an unknown mech­a­nism.”

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After years of lab work, the researchers iso­lated the CBP60g gene, which can with­hold the pro­duc­tion of the sal­i­cylic acid hor­mone in plants when tem­per­a­tures rise, neu­tral­iz­ing their defense mech­a­nism. The solu­tion genet­i­cally bypassed the gene to restore the plan­t’s defense at hot­ter tem­per­a­tures.

This was a multi-year and multi-insti­tu­tional effort,” Christian Danve Castroverde, a biol­o­gist at the Wilfrid Laurier University in Canada and co-author of the study, told Olive Oil Times.

In 2013, [we] dis­cov­ered that short peri­ods of high tem­per­a­ture dra­mat­i­cally impact the hor­mone defenses of Arabidopsis plants against infec­tion by a bac­terium called Pseudomonas syringae,” he added. After sev­eral more years, we were even­tu­ally suc­cess­ful in iden­ti­fy­ing the mol­e­c­u­lar basis of how Arabidopsis immu­nity is sup­pressed by warm tem­per­a­ture con­di­tions.”

The researchers bypassed the gene in the lab by adding a pro­moter.’ The short DNA sequence forces the gene to tran­scribe (copy the DNA sequence into an RNA mol­e­cule), restor­ing Arabidopsis thaliana’s abil­ity to pro­duce the sal­i­cylic acid hor­mone.

Including the sal­i­cylic acid recep­tor and biosyn­thetic genes, opti­mized CBP60g expres­sion was suf­fi­cient to broadly restore sal­i­cylic acid pro­duc­tion, basal immu­nity and effec­tor-trig­gered immu­nity at the ele­vated growth tem­per­a­ture with­out sig­nif­i­cant growth trade-offs,” the researchers wrote.

See Also:Researchers Work to Identify Olive Varieties Best Adapted to Higher Temperatures

The team has started test­ing gene mod­i­fi­ca­tion on food crops such as rape­seed. They also plan to exper­i­ment with more crops, includ­ing wheat and pota­toes. However, Castroverde said a sig­nif­i­cant amount of field research is required before apply­ing the fix at a large scale.

Many plants have CBP60g-like genes, and a lot of them have the capac­ity to make sal­i­cylic acid,” he said. It looks like plants already have a weapon in their arse­nal. Our chal­lenge now is just har­ness­ing this power. In terms of agri­cul­tural appli­ca­tions, I believe we have to wait until we have suc­cess­ful results in field tri­als.”

Nevertheless, the spe­cific solu­tion pro­posed by the research team to restore the plant immune sys­tem pre­sup­poses that con­sumers are ready to accept more genetic manip­u­la­tion of their food.

As cli­mate change accel­er­ates, we’re going to be under pres­sure to learn things in the lab and move them into the field faster,” said Marc Nishimura, an expert in plant immu­nity at Colorado State University, who was not involved in the research. I can’t see how we’re going to do this with­out more accep­tance of genet­i­cally mod­i­fied plants.”

Another study pub­lished by researchers at the Chinese University of Hong Kong in June warned that crop yields could decrease by 20 per­cent glob­ally by 2050 due to ozone pol­lu­tion and the effects of cli­mate change

Despite their suc­cess in restor­ing the Arabidopsis thaliana’s defense against heat, the researchers stressed the fact that the gap in under­stand­ing how a warm­ing cli­mate influ­ences the effec­tive­ness of the plant immune sys­tem is a key con­cern for future agri­cul­tural pro­duc­tiv­ity, ecosys­tem preser­va­tion and the emer­gence of new plant dis­ease pan­demics.”

However, they added that their results point to crops becom­ing more resis­tant in the future.

We were able to make the whole plant immune sys­tem more robust at warm tem­per­a­tures,” said He, the plant biol­o­gist from Duke. If this is true for crop plants as well, that’s a really big deal because then we have a very pow­er­ful weapon.”



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