WRKY70 Negatively Regulates SARD1, a Positive Regulator of SA Synthesis 
M. ZHOU (1), Y. Lu (1), J. Glazebrook (1) (1) Department of Plant Biology, Microbial and Plant Genomics Institute, University of Minnesota, U.S.A.

SYSTEMIC ACQUIRED RESISTANCE DEFICIENT 1 (SARD1) encodes a positive regulator that promotes the production of salicylic acid (SA) and affects the expression of both SA-dependent and SA-independent downstream defense genes. Upon pathogen recognition, SARD1 is strongly induced. The transcription factors that control this induction are still unknown. Here, we seek to identify the potential transcriptional regulators of SARD1 using cis-regulatory element analysis and yeast one-hybrid screening against a collection of Arabidopsis transcription factors involved in plant immunity. By scanning five fragments of the SARD1 promoter, we found that WRKY70 can bind to a fragment of the SARD1 promoter extending from -451 bp to 1 bp relative to the translational start site. Electrophoretic Mobility Shift Assays (EMSA) indicated that WRKY70 can bind to a 25 bp fragment within this interval that contains a “GACTTTT” motif. EMSA mutation analysis indicated that the “GACTTTT” motif is critical for WRKY70 binding. The wrky70-1 and wrky70-3 mutants are more resistant than wild-type Col-0 to the bacterial pathogen Pseudomonas syringae pv. maculicola (Pma) ES4326. SA levels and expression of SARD1 in wrky70-1 and wrky70-3 mutants are also significantly higher than in wild-type Col-0. We hypothesize that WRKY70 is a negative regulator of SA biosynthesis acting in part through the negative regulation of SARD1. 

Abstract Number: P16-484
Session Type: Poster