Grapevine protein Src2 mediates plant disease resistance during <i>Lasiodiplodia theobromae</i> infection

Lysin motif (LysM) effectors contribute to the virulence of many pathogens, but the underlying mechanism of this type of effector remains poorly understood. Here, we identified a LysM-containing protein, named LtLysM2, in the plant opportunistic pathogen Lasiodiplodia theobromae. We demonstrated that LtLysM2 contributes to the virulence of the pathogen, is able to bind to chitin oligosaccharides, and can suppress chitin-triggered plant immune responses. Importantly, we showed that the grapevine (Vitis vinifera) protein VvSrc2, a membrane- and nuclear-localized protein homologous to the soybean (Glycine max) protein Src2 (Soybean genes regulated by cold 2), interacts with LtLysM2. Interestingly, the nuclear accumulation of VvSrc2 was elevated in the presence of LtLysM2. Ectopic expression of VvSrc2 in Nicotiana benthamiana enhanced resistance to L. theobromae. Additionally, the VvSrc2 protein interacted with the nuclear-localized RNA-binding protein VvUbp1, contributing to the programmed cell death evoked by VvUbp1. Our findings reveal a previously uncharacterized regulatory pathway in which VvSrc2 is upregulated after the recognition of LtLysM2 and serves as an intermediator to transduce extracellular signaling events into nuclear components during infection by L. theobromae through association with the downstream target VvUbp1 in the cell nucleus.