The cell death-inducing protein BcPlp1 from Botrytis cinerea contributes to pathogenicity and modulates plant resistance

Abstract

Botrytis cinerea is a necrotrophic plant pathogen fungus with a broad host range, causing grey mould and rot diseases in many important crops, leading to significant economic losses in agriculture. Cell death-inducing proteins (CDIPs) secreted by necrotrophic phytopathogens promote plant tissue death and play important roles in infection. However, the mechanisms by which CDIPs induce cell death in B. cinerea-plants interactions remain unclear. Here, we demonstrate that the B. cinerea CDIP BcPlp1 is secreted into the plant apoplast where it induces cell death. BcPlp1 is a cysteine-rich protein, and four out of the 8 cysteine residues and a conserved N-terminal α-helix structure are essential for its cell death-inducing activity. A purified GST-tagged BcPlp1 fusion protein triggered cell death in multiple plant species, up-regulated expression of defense-related genes and enhanced plant resistance to B. cinerea. Additionally, the cell death-inducing activity of BcPlp1 was mediated by leucine-rich repeat (LRR) receptor-like kinases BAK1 and SOBIR1. Furthermore, BcPlp1 was not necessary for colony morphology, conidial production, growth rate, and stress tolerance. Although deletion of BcPlp1 did not affect virulence, its overexpression led to larger disease lesion, highlighting its contribution to B. cinerea pathogenicity when upregulated.