Identification and characterization of small-molecules that inhibit plant immune responses
N. ISHIHAMA (1), Y. Noutoshi (2), S. Choi (3), I. Saska (3), S. Asai (3), B. Huot (4), S. He (4), K. Shirasu (3) (1) RIKEN Center for Sustainable Resource Science, Japan; (2) Graduate School of Environmental and Life Science, Okayama University, Japan; (3) RIKEN Center for Sustainable Resource Science, Japan; (4) Department of Energy Plant Research Laboratory, Michigan State University, U.S.A.

Chemical biology is an expanding discipline that utilizes bioactive small molecules to elucidate biological mechanisms. In addition, it has a possibility to overcome limitations in classical genetic methods, such as lethality and functional redundancy. We applied a chemical biology approach to investigate Arabidopsis immune responses to Pseudomonas syringae pv. tomato (Pst) DC3000 avrRpm1. We have developed a high-throughput screening method to identify small-molecule potentiators or inhibitors of plant immune responses (Noutoshi et al., Plant Cell, 2012). Using 2,768 compounds from two libraries of pharmaceuticals and natural products, we identified three structurally related inhibitor compounds of plant immune responses. Interestingly, Arabidopsis plants treated with these inhibitors, designated as P7, P8 and P9, significantly increased susceptibility to Pst DC3000. P7 suppressed the expression of SA marker gene, PR1, in response to both Pst DC3000 infection and SA treatment. Furthermore, the nuclear accumulation of NPR1, a central regulator of SA signaling pathway, was also suppressed by P7. These results suggest that P7 targets the SA-dependent signaling pathway upstream of NPR1.

Abstract Number: P18-676
Session Type: Poster