A Necrotrophic Phytopathogen-Derived GPI-Anchored Protein Functions as an Elicitor to Activate Plant Immunity and Enhance Resistance.

GPI-anchored proteins are widely distributed in eukaryotic cells. However, their functions are still poorly understood in necrotrophic pathogenic fungi. Here, based on Agrobacterium tumefaciens-mediated transient expression screening, a novel secreted GPI-anchored protein, SsGP1, that induces plant cell death was characterised in Sclerotinia sclerotiorum. The homologues of SsGP1 are broadly distributed among ascomycetes. SsGP1 can activate plant immune responses, including reactive oxygen species (ROS) burst and the up-regulated expression of immunity genes, in a manner that is dependent on BAK1 but independent of SOBIR1. Treatment of plants with SsGP1 protein enhanced the resistance of Nicotiana benthamiana and Arabidopsis thaliana to S. sclerotiorum. Our findings reveal that SsGP1 functions as a pathogen-associated molecular pattern (PAMP) and is recognised by plants in a BAK1-dependent manner.