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Cytokinin-regulated transcriptional networks regulating plant development and defense

Cristiana Argueso: Colorado State University

<div>During activated states of immunity plants often display a tradeoff between defense and growth. High levels of defense activation leads to reduced shoot growth and also reduced seed set. This phenomenon is observed in Arabidopsis, and many other plant species, however the mechanisms behind growth defense tradeoffs are mostly unknown. Hormone signaling networks are responsible for regulating growth and development, as well as plant-pathogen interactions. To identify possible molecular mechanisms modulating the growth defense trade-off in plants we focused on the plant growth hormone cytokinin, widely known for a role in plant growth and development and for which a role in defense responses to biotrophic pathogens has been recently demonstrated. We used a computational biology approach to analyze transcriptional data for regulators of plant growth-defense tradeoffs. With this approach we identified a class of transcription factors that are important for cytokinin-promoted plant growth, and whose expression is rapidly reduced during defense activation. Genetic analyses showed that mutations in these genes leads to increased resistance to bacterial and oomycete pathogens, as well as increased defense gene expression. Overexpression of these genes positively affects plant growth. We propose that these transcription factors may function as a switch between growth and defense, through the regulation of cytokinin-regulated transcriptional targets that prioritize plant growth over defense activation.</div>