Genetic discovery may help plants survive heatwaves

New research published this week in Nature advances plants’ resilience to rising global temperatures. The study, led by researchers at Duke University, US, highlights a gene that controls plant responses to heatwaves.

Food security is a key challenge facing our world. With up to 40% of global food crops already lost to pests and disease annually, and an ongoing climate crisis, we need more tools in our toolbox to ensure we can feed the world’s growing population.

High temperatures negatively impact plants’ natural defence systems, making them more vulnerable to infection by pathogens such as bacteria. Under normal temperatures, a bacterial incursion will cause plants to produce high levels of a hormone called salicylic acid, which activates an immune response against the invader.

However, even brief heatwaves can cause this defence mechanism to fail. Arabidopsis thaliana (thale cress), a plant “model organism” commonly used in lab research, is unable to produce enough salicylic acid to stave off an infection with the bacterium Pseudomonas syringae after just two days of exposure to temperatures above 30°C.

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

In the new study, co-first authors Jonghum Kim of Duke University and Danve Castroverde of Michigan State University examined gene expression in infected A. thaliana plants under normal and elevated temperature conditions (23 and 28°C, respectively). Many of the genes that were downregulated at the higher temperature were under the control of a single gene, CBP60g, which acts as a switch that turns other genes on and off.

The study further showed evidence that proteins and other cellular components that allow the production of CBP60g were unable to assemble correctly at higher temperatures. Without CBP60g production, the genes that CBP60g controls are also downregulated – including proteins that enable salicylic acid build-up.

However, mutant plants that have CBP60g constantly switched on are still able to produce salicylic acid and resist bacterial infection at high temperatures. Because there is a trade-off between the resources a plant can put into its growth and immune system, He and colleagues also worked on developing a system where Arabidopsis could switch on CBP60g only when challenged by infection, not all the time.

Importantly, higher temperatures are also known to reduce salicylic acid defences in tomatoes, canola and rice. Successfully translating the Arabidopsis results into crops like these would be a big win for food security.

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