3-Aminobenzamide inhibits callose deposition and alters PMR4 callose synthase abundance independently of poly(ADP-ribosyl)ation
B. KEPPLER (1), J. Song (1), A. Bent (1) (1) University of Wisconsin, U.S.A.

A chemical inhibitor of poly(ADP-ribosyl)ation, 3-aminobenzamide (3AB), blocks certain plant responses to microbe-associated molecular patterns (MAMPs, such as flg22), including cell wall reinforcement with callose. Poly(ADP-ribosyl)ation is a post-translational modification in which chains of ADP-ribose are added to a target protein by poly(ADP-ribose) polymerases (PARPs), and is well known for its roles in DNA damage repair. In contrast to the callose disruption observed with 3AB, a parp1parp2parp3 triple mutant does not significantly impact callose deposition. Additionally, the more potent and specific PARP inhibitors PJ-34 and INH2BP inhibit PARP activity in Arabidopsis, but do not block MAMP-induced callose deposition. These data suggest that 3AB inhibits callose deposition through a mechanism independent of poly(ADP-ribosyl)ation. Powdery Mildew Resistant 4 (PMR4) is the callose synthase responsible for virtually all MAMP and wound-induced callose deposition in Arabidopsis. Levels of PMR4-HA protein (under control of PMR4 promoter sequences) increase in response to flg22. Interestingly, 3AB alone reduces PMR4-HA protein abundance, but in response to flg22, PMR4-HA levels increase even more in the presence of 3AB, despite no callose being produced. Hence 3AB remains a powerful tool in our ongoing work to identify novel regulators of MAMP-induced callose deposition.

Abstract Number: P15-427
Session Type: Poster