Figure 5. AvrB Interacts with MPK4.
(A) AvrB interacts with MPK4 in vitro. Equal amounts of AvrB-His or AvrBD297A-His were incubated with GST or GST-MPK4, and the presence of AvrB after GST pull-down was detected by immunoblot using anti-His antibody. (B) AvrB-3xFLAG interacts with MPK4 in plants in a RAR1-dependent manner. RAR1/rpm1 (RAR1) or rar1-29/rpm1 (rar1) plants with or without the AvrB-3xFLAG transgene were induced with estradiol, and protein extracts were immunoprecipitated with agarose-conjugated anti-FLAG antibody. The presence of MPK4 in the immune complex was detected by immunoblot using anti-MPK4 antibodies. (C) RAR1 is required for AvrB-3xFLAG-induced MPK4 phosphorylation. Plants of the indicated genotypes were induced with estradiol, and the phosphorylation state of immunoprecipitated MPK4 was determined by immunoblot using anti-phospho-ERK1 antibodies.