The Fungal Transcription Factor BcTbs1 from Botrytis cinereaPromotes Pathogenicity via Host Cellulose Degradation

Zn(II)2Cys6 proteins constitute the largest group of fungal-specific transcription factors. However, little is known about their functions in the crop killer Botrytis cinerea. In this work, a T-DNA insertion strain M13448 was identified which was inserted into the Zn(II)2Cys6 TF-encoding gene BcTBS1. Knockout of BcTBS1did not affect mycelia growth, appressorium formation, and sclerotium germination, but impaired fungal conidiation, conidial morphogenesis, conidial germination, infection cushion development, and sclerotial formation. Accordingly, ΔBctbs1mutants showed reduced virulence in its host plants. Further study proved that BcTBS1, BCIN_15g03870, and BCIN_12g06630were induced by cellulose. Subsequent cellulase activity assays revealed that the loss of BcTBS1significantly decreased cellulase activity. In addition, we verified that the BCIN_15g03870and BCIN_12g06630genes were positive regulated by BcTBS1by quantitative real-time reverse-transcription-polymerase chain reaction (qRT-PCR). Taken together, these results suggested that BcTBS1can promote pathogenicity by modulating cellulase-encoding genes that participate in host cellulose degradation.