RS_CRZ1, a C2H2 type transcription factor is required for pathogenesis of Rhizoctonia solani AG1-IA in tomato.

Rhizoctonia solani is a necrotrophic fungal pathogen which causes disease in diverse plant species. In recent years, the genomic and transcriptomic studies have identified several candidate pathogenicity determinants of R. solani; however, most of them remain to be validated. In this study, we report a viral vector-based host induced gene silencing (HIGS) as well as a dsRNA (double stranded RNA) based approach to effectively downregulate genes of R. solani AG1-IA (BRS1 strain) during pathogenesis in tomato. We tested a few of the in-planta upregulated R. solani genes and observed that silencing of one of them i.e. RS_CRZ1 (a C2H2 type Zn finger transcription factor) significantly compromises the pathogenesis of R. solani in tomato. The RS_CRZ1 silenced plants not only exhibited significant reduction in disease symptoms, but the depth of pathogen colonization was also compromised. Furthermore, we identified the R. solani genes that were co-regulated with RS_CRZ1 during pathogenicity process. The HIGS mediated silencing of a few of them (CL1756Contig1; subtilisin like protease and CL1817Contig2; 2OG- Fe(II) oxygenase) compromised the pathogenesis of R. solani in tomato. The ectopic expression of RS_CRZ1 complemented the crz1 mutant of yeast and restored tolerance against various metal ion stress. Overall, our study reveals the importance of RS_CRZ1 in managing the hostile environment encountered during host colonization. Also, it emphasizes the relevance of HIGS and dsRNA-based gene silencing approach towards functional characterization of pathogenicity determinants of R. solani.