Abscisic acid regulates TSRF1-mediated resistance to Ralstonia solanacearum by modifying the expression of GCC box-containing genes in tobacco.

Although recent studies have established a significant regulatory role for abscisic acid (ABA) and ethylene response factor (ERF) proteins in plant pathogen resistance, it is not clear whether and how ABA performs this role. Previously, it was reported that an ERF protein, TSRF1, activates the expression of GCC box-containing genes and significantly enhances the resistance to Ralstonia solanacearum in both tobacco and tomato plants. Here, it is reported that TSRF1-regulated pathogen resistance is modified by ABA application. TSRF1 activates the expression of ABA biosynthesis-related genes, resulting in the increase of ABA biosynthesis, which further stimulates ethylene production. More interestingly, ABA application decreases, while the inhibitor of ABA biosynthesis fluridone increases, the TSRF1-enhanced resistance to R. solanacearum. This observation is further supported by the finding that ABA and fluridone reversibly modify the ability of TSRF1 to bind the ethylene-responsive GCC box, consequently altering the expression of element-controlled genes. These results therefore establish that TSRF1-regulated resistance to R. solanacearum can be modified in tobacco by ABA.