ORIGINAL ABSTRACT

Sheath blight disease of rice caused by the fungal pathogen R. solani AG1-IA remains a big threat to rice production worldwide. A limited genetic variation in rice for tolerance to this pathogen and little success in understanding how it defeats host defence are major reasons behind it. In this study, we attempted to decode the virulence spectrum of R. solani AG1-IA in rice using time-course transcriptome analysis and functional genomics tools. Several stage-specific and commonly expressed genes were identified. Notably, the shikimate pathway emerged as an important pathway and was implicated in the virulence of R. solani AG1-IA. Inhibition of the shikimate pathway by glyphosate, a known inhibitor of 5-enolpyruvylshikimate-3-phosphate (EPSP) synthase, reduced the vegetative growth of R. solani AG1-IA and several other phytopathogens. Our results were complemented by in vitro inhibition studies of RsEPSP synthase using a recombinantly expressed protein. Comparative sequence analysis of RsEPSP synthase with plants and known major phytopathogens revealed a distinct region in RsEPSP synthase. Using Nicothaiana benthamiana as a model system and stable rice transgenic lines, we demonstrated that targeting this distinct region through host-induced gene silencing (HIGS) compromises the growth and virulence of R. solani AG1-IA. The study lays a foundation for a deeper understanding of the identified virulence genes and establishes the shikimate pathway as a central target to control phytopathogens.