Involvement of the Rice OsSAUR51 Gene in the Auxin-related Field Resistance Mechanism against Bacterial Blight Disease

摘要

Pathogenic infection causes auxins to accumulate in plant cells and suppresses plant defense systems. We isolated the OsSAUR51 (Oryza sativa small auxin-up RNA 51) gene as one of the rice field resistance-related genes from a retrotransposon Tos17-tagged ‘Nipponbare’ mutant (XC20) in which field resistance was reduced against several races of bacterial blight pathogens. OsSAUR51 expression was induced by infection of the pathogen and exogenous auxin treatment, whereas the OsSAUR51 gene in the XC20 insertion mutant lost its function due to the Tos17 insertion. We transformed the OsSAUR51 gene with the 1.0 kb OsSAUR51 native promoter into XC20 for complementation analysis and also introduced the OsSAUR51 gene controlled by RexPhi, an enhanced CaMV 35S promoter, into the rice cultivar ‘Dontokoi’ to make transgenic plants with enhanced expression of the OsSAUR51 gene. The OsSAUR51-transformed XC20 recovered its bacterial blight resistance, and the RexPhi::OsSAUR51-transformed ‘Dontokoi’ showed enhanced bacterial blight resistance as compared to untransformed ‘Dontokoi’. Auxin accumulation after the bacterial blight inoculation of XC20 was comparatively higher than that of ‘Nipponbare’, but the auxin levels of ?OsSAUR51-transformed XC20 were lower than those of untransformed XC20. Auxin accumulation after bacterial blight infection in the RexPhi::OsSAUR51-transformed ‘Dontokoi’ plants was repressed as compared to untransformed‘Dontokoi’. These results suggest that the OsSAUR51 gene induces a field resistance mechanism and represses auxin?ccumulation after bacterial blight pathogen infection.