Plants Employ an “Activation by Destruction” Mechanism to Regulate Immune Responses

Jasmonic acid (JA) is a fatty acid-derived plant hormone that regulates a broad range of plant defense responses against herbivores, wounding and pathogen attack. JA signaling triggers an important transcriptional reprogramming of plant cell to modulate stress responses. The Arabidopsis thaliana basic helix-loop-helix Leu zipper transcription factor MYC2 is a master regulator in Jasmonate (JA) signaling pathway. MYC2 differentially regulates JA responsive wound response (e.g., VSP1, LOX2) genes and pathogen defense (e.g., PDF1.2). Although MYC2-mediated transcriptional regulation plays a central role in different aspects of JA-mediated immunity, how MYC2 itself is regulated at the protein level remains elusive.

Scientists in Dr. Chuanyou Li’s group from the Institute of Genetics and Development Biology, the Chinese Academy of Sciences, provided evidence that phosphorylation-dependent turnover of MYC2 is coupled with its function. They showed that, during JA response, high accumulation of the MYC2 protein co-relates with peaked expression of early wound-responsive genes that are positively regulated by MYC2, whereas low accumulation of the MYC2 protein co-relates with peaked expression of late pathogen-responsive genes that are negatively regulated by MYC2.

They discovered a 12-amino-acid element in the transcription activation domain of MYC2 that is required for both the proteolysis and the transcriptional activity of MYC2. Interestingly, MYC2 phosphorylation at residue Thr328, which facilitates its turnover, is also important for the MYC2 function to regulate transcription. Together, these results reveal that phosphorylation and turnover of MYC2 is tightly linked with its function to regulate the transcription of JA-responsive genes.

These findings exemplify that plants employ proteolysis-coupled transcription as mechanism to fine tune their responses to versatile stresses.

This work with Dr. Qingzhe Zhai as the first author has been online published on PLoS Genetics (DOI: 10.1371/journal.pgen.1003422). This research was supported by grants from The Ministry of Agriculture of China, The Ministry of Science and Technology of China and the National Natural Science Foundation of China.

AUTHOR CONTACT:

Chuanyou Li, Group Leader

Institute of Genetics and Developmetnal Biology, Chinese Academy of Sciences, Beijing, China.

E-mail: cyli@genetics.ac.cn