The BcSDR1 gene is required for growth, development, and pathogenicity of Botrytis cinerea

The sclerotia-deficiency mutant BCt41 was found in the Agrobacterium tumefaciens-mediated transformation mutant library of Botrytis cinerea. The mutant gene of BCt41 was isolated and identified as BcSDR1, encoding a B. cinerea protein with unknown function. The BCt41 mutant had a significantly weakened pathogenicity compared to wild-type (WT) and BcSDR1-complementing mutant (BCt41/BcSDR1). Both phenotype and pathogenicity of BcSDR1-complementing mutant were similar to those of WT. The activity of cell wall degrading enzymes (CWDE) was significantly lower in the BCt41 mutant than in both WT and BCt41/BcSDR1. The toxin activity and acid production of the BCt41 mutant were also significantly reduced. However, appressoria of the BCt41 mutant appeared significantly different to that of WT and BCt41/BcSDR1. The BCt41 mutant sensitivity to NaCl, KCl, and Fluconazole were remarkably increased compared to WT and BCt41/BcSDR1. The expression levels of the key genes of the cAMP and MAPK signaling pathways were noticeably up-regulated in the BCt41 mutant. These results indicated that the BcSDR1 gene positively influences mycelia growth, sclerotia development, and pathogenicity, while it negatively regulates conidia formation of B. cinerea. The BcSDR1 gene is involved in the regulation of CWDEs, toxin, acid production, and the cAMP and MAPK signaling pathways.