Membrane Protein Bcest Is Involved in Hyphal Growth, Virulence and Stress Tolerance of Botrytis cinerea

Grey mold caused by Botrytis cinerea is a devastating disease responsible for large losses to agricultural production, and a necrotrophic model fungal plant pathogen. As important targets of fungicides, membrane proteins are hot spots in the research and development of fungicide products. Wuyiencin affects the permeability and pathogenicity of B. cinerea , and the membrane protein Bcest was found to be associated by parallel reaction monitoring. To explore this relationship, the bacteriostatic mechanism of wuyiencin was elucidated. In the present work, we generated and characterised Δ Bcest deletion mutants of B. cinerea and constructed complemented strains. The Δ Bcest deletion mutants exhibited reduced conidia germination and germ tube elongation. The functional activity of Δ Bcest deletion mutants was illustrated by reduced necrotic colonisation of B. cinerea on strawberries and grapes fruits. Targeted deletion of Bcest also blocked several phenotypic defects in aspects of mycelial growth, conidiation and virulence. All phenotypic defects were restored by targeted gene complementation. The role of Bcest in pathogenicity was also supported by reverse transcriptase real-time quantitative PCR (qRT-PCR) results, which indicated that the melanin synthesis gene Bcpks13 and the virulence factor Bccdc14 were significantly downregulated in the early infection stage of the Δ Bcest strain. Taken together, these results suggest that Bcest plays important roles in the regulation of various cellular processes in B. cinerea .