Proteome-wide identification of protein poly(ADP-ribosyl)ation targets reveals an important role of FHA domain protein DAWDLE in Arabidopsis immunity.
P. HE (1), B. Feng (1), S. Ma (2), S. Chen (3), S. Zhang (4), B. Yu (4), S. Dinesh-Kumar (2), L. Shan (1) (1) Texas A&M University, U.S.A.; (2) University of California, Davis, U.S.A.; (3) University of Florida, U.S.A.; (4) University of Nebraska, U.S.A.

Perception of microbe-associated molecular patterns (MAMPs) elicits a rapid and profound transcriptional reprogramming, which is central for launching an effective host defense to pathogen invasions. The molecular mechanisms orchestrating immune gene activation are not fully understood. Through a genetic screen in Arabidopsis, we recently demonstrated that protein poly(ADP-ribosyl)ation (PARylation) plays a pivotal role in controlling plant immune gene expression and defense to pathogen attacks. PARylation is a reversible post-translational modification primarily mediated by poly(ADP-ribose) polymerase (PARP) and poly(ADP-ribose) glycohydrolase (PARG). The Arabidopsis parp mutant displayed reduced, whereas parg mutant displayed enhanced immune gene activation and immunity to multiple pathogens. We further deployed an Arabidopsis protein microarray coupled with in vitro PARylation to globally identify PARylation targets in plants. In line with nuclear localization of Arabidopsis PARPs, 56% of PARylation targets are predicted to localize in nucleus. Consistent with the essential role of protein PARylation in plant innate immunity, forkhead-associated (FHA) domain protein DAWDLE (DDL), one of the PARylation targets, positively regulates plant defense to both adapted and non-adapted pathogens. Arabidopsis PARP2 interacts and PARylates DDL, which was enhanced upon MAMP treatment. Mass spectrometry and mutagenesis analysis identified multiple PARylation sites of DDL by PARP2. Genetic complementation assays indicate that DDL PARylation is required for its function in plant immunity. In contrast, DDL PARylation appears to be dispensable for its previously reported function in plant development partially mediated by the regulation of microRNA biogenesis. Our study uncovers many previously unknown PARylation targets and points to the distinct functions of DDL in plant immunity and development mediated by protein PARylation and small RNA biogenesis respectively.

Abstract Number: P17-532
Session Type: Poster