Cerato-platanin family proteins are secreted and have been found both in the fungal cell wall and in the extracellular medium. They elicit defence responses in a variety of plants and have been proposed to be perceived as PAMPs by the plant immune system, although in the case of the necrotroph Botrytis cinerea the cerato-platanin BcSpl1 contributes to fungal virulence instead of plant resistance. In this study we report that BcSpl1, which we previously found in the secretome as an abundant protein, is even more abundant in the fungal cell wall. By fusion to GFP, we also show that BcSpl1 associates with the plant plasma membrane causing rapid morphological changes at the cellular level, such as disorganization o... More
Cerato-platanin family proteins are secreted and have been found both in the fungal cell wall and in the extracellular medium. They elicit defence responses in a variety of plants and have been proposed to be perceived as PAMPs by the plant immune system, although in the case of the necrotroph Botrytis cinerea the cerato-platanin BcSpl1 contributes to fungal virulence instead of plant resistance. In this study we report that BcSpl1, which we previously found in the secretome as an abundant protein, is even more abundant in the fungal cell wall. By fusion to GFP, we also show that BcSpl1 associates with the plant plasma membrane causing rapid morphological changes at the cellular level, such as disorganization of chloroplasts, prior to the macroscopic necrosis in the treated tissue. By a combination of serial deletion studies, synthetic peptides, and chimeric proteins, we mapped the eliciting activity to a two-peptide motif in the protein surface. The expression of a chimeric protein displaying this motif in B. cinerea mutants lacking BcSpl1 undoubtedly showed that the motif is responsible for the BcSpl1 contribution to virulence.
