AtMYB44 Modulates Cross-talk Between JA and SA by Regulating WRKY70 Expression

Jasmonates play important roles in development, stress responses and defense in plants. Transcription factors are critical regulators of the changes in gene expression that drive developmental processes and environmental stress responses. AtMYB44 belongs to the R2R3 MYB transcription factor subgroup 22 family in Arabidopsis thaliana. AtMYB44 is rapidly induced by jasmonate. To test whether JA-mediated responses are affected by AtMYB44, the role of AtMYB44 in root growth and accumulation of anthocyanin were characterized. Gain or loss of AtMYB44 function causes opposite effect on JA-mediated responses. While overexpression of AtMYB44 caused reduced response to JA, knock-out mutation of AtMYB44 increased response to JA. Expression of JA responsive marker genes, including AOS, VSP1 and PDF1.2 were suppressed in the 35S:AtMYB44 and increased in atmyb44 plant under MeJA treatment. Negative regulation of JA response by AtMYB44 affected to salicylic acid (SA) response. AtMYB44 overexpression plants showed disease resistance to virulent pathogen. PR genes and WRKY70 were constitutively activated in AtMYB44 overexpression plants. These altered response to JA and SA in AtMYB44 overexpression plants were recovered by crossing with NahG but not npr1-1 plants. AtMYB44 is required for NPR1 independent early induction of WRKY70. In gel mobility shift assay, AtMYB44 binds to promoter of WRKY70. From these data, we suggest that AtMYB44 regulate cross-talk between JA and SA by regulating WRKY70 expression.