Genetic suppressor screen and transcriptional profiling elucidate the PBS3 node of plant immunity in Arabidopsis thaliana
R. MACKELPRANG (1), R. Ramos (1), M. Wildermuth (1), R. Okrent (2) (1) University of California, Berkeley, U.S.A.; (2) USDA-ARS Forage Seed and Cereal Research Unit, U.S.A.

Salicylic acid (SA) is indispensable for induction of robust plant defense against (hemi)biotrophic microbial pathogens. In Arabidopsis thaliana, the cellular concentration of SA remains low in the absence of pathogenic challenge but increases in the hours and days post infection. SA binds to the defense master regulator NPR1, transcriptionally regulating the induced immune response, including induction of defense-marker PR1. Multiple labs converged on PBS3 (also called GDG1, WIN3, GH3.12) as necessary for induced total SA accumulation and robust defense. In addition, pbs3-2, similar to npr1-1, exhibits early flowering. Yet a mechanism by which PBS3 regulates SA metabolism, defense, and flowering has remained elusive. PBS3 is a member of the GH3 family of adenylating enzymes. We previously showed that PBS3 prefers 4-substituted benzoic acids and is inhibited by SA, which does not clarify its role in defense. To elucidate the effect of PBS3 on plant defense and avoid potential complications from pathogen effectors, we employed UV-C as an elicitor of SA accumulation and defense, followed by time series transcriptional analyses. To elucidate its function, we performed a pbs3 suppressor screen to look for restored UV-C induced PR1 expression. We identified suppressor mutants that restore i) wild type induced defense and flowering time and ii) exclusively wild type induced defense, providing insight into the PBS3 node of plant immunity and its intersection with flowering time.

Abstract Number: P16-460
Session Type: Poster