Salicylic acid is key to protecting plants from everything from extreme temperatures to diseases. But increasing this naturally occurring chemical typically results in stunted plant growth.

A University of Georgia research team recently discovered a way to jump the salicylic acid hurdle and increase levels in poplars without a negative impact on growth, potentially paving the way for better-growing crops and trees.

In a paper recently published in Plant Cell, the team outlined how their approach differs from previous attempts to increase salicylic acid levels in plants while avoiding growth stagnation.

"It's such an important hormone," said C.J. Tsai, a UGA professor with joint appointments in the Warnell School of Forestry and Natural Resources and the Franklin College of Arts and Sciences department of genetics. "People have gone after this for a long time, but previous attempts to increase the levels of salicylic acid have often had unwanted side effects. We're very excited about the possibilities our method has, particularly because it has a lot of potential for both trees and crops."

Salicylic acid regulates plant systems like photosynthesis and defense against abiotic and biotic stresses-temperature, drought and disease.

First, Tsai's former postdoctoral student Yinan Yuan developed a new strategy for increasing the salicylic acid levels by testing a bi-functional bacterial gene in poplar. This included obtaining the gene and designing the proper expression vectors for introduction into the plants.

They then used what they learned from other work they were conducting in the lab—developing genomics tools that included transcriptomics (gene expression), metabolomics (unbiased analysis of metabolites) and computational data analysis pipelines—to analyze their results, which required Liang-Jiao Xue, a bioinformatics postdoctoral research associate, to build the metabolite and gene networks they needed to dissect the complex regulation. Metabolites are produced by a living organism's metabolism and have a number of functions, including defense and growth.

"This was truly a team effort, with many former and current lab members contributing expertise to the project," Tsai said.

They found many metabolites and genes previously associated with salicylic acid regulation and then discovered many more that, before this study, have never been identified. They will use these findings in future experiments.

"It will be interesting to see how these metabolites and genes are regulated in multiple species under both normal and stress conditions, as this will provide more clues on how plants adapt to a changing environment," Xue said.

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