Rhizospheric pathogen proliferation and ROS production is associated with premature senescence of the osvha-a1 rice mutant

Root-pathogen interactions are an important factor influencing premature senescence in rice, however, few studies have addressed the underlying mechanism. In this study, when premature senescence significantly occurred in the OsVHA-A1 mutant (loss of tonoplast H +ATPase activity), the relative abundance of rhizospheric bacterial communities were similar between the mutant and its WT while the fungi in the rhizosphere of the OsVHA-A1 mutant significantly differed from the WT. Furthermore, we found that one key fungal strain, named Gibberella intermedia, in the rhizospheric soil of the OsVHA-A1 mutant increased largely during the late growing phase, as compared to the WT and G. intermedia was shown to rapidly colonize the root of the OsVHA-A1 mutant resulting in severe ROS accumulation. But, the reverse was true in the case of the WT, indicating a much lower ROS level than those of the mutant when infected by G. intermedia. By using High Performance Liquid Chromatography (HPLC), we found that sugars in root exudates from the OsVHA-A1 mutant were different from sugars in root exudates from the WT. G. intermedia could efficiently use mannose and rhamnose in root exudates from the mutant better than other sugars. Finally, antagonistic bacteria could be employed for limiting the proliferation of G. intermedia in rhizosphere, thereby alleviating the early senescent phenotypes of the OsVHA-A1 mutant rice and improving the grain yield.