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Abstract:
To increase virulence, plant pathogenic effectors disturb the ubiquitin-proteasome system and autophagy proteolytic pathways by interfering with host cellular functions. We studied the bacterial pathogen Xanthomonas campestris pv. vesicatoria (Xcv), a significant agricultural pest. We demonstrated that the Xcv type-III effector, XopL, inhibits host autophagy. XopL interacts with and ubiquitinates a component of the host autophagic machinery, SH3P2. This causes SH3P2 to be degraded by the proteasome, perturbing host autophagy and enhancing Xcv bacterial growth. In turn, the plant uses NBR1, a defense-related selective autophagy receptor, to defend itself triggering XopL degradation through a process termed “effectorphagy”. However, we discovered that this connection is driven by both ubiquitin- dependent and -independent interaction. This suggests another layer, apart from “effectorphagy”, in NBR1-mediated immunity. To unravel the tight regulation of this component, we aim to understand the dynamic of Ubiquitin-dependent and -independent NBR1 interactome in an infection context. In response to Xcv infection, we identified multiple post translational modifications as well as novel interactors involved in protein degradation, plant immunity, trafficking and cytoskeleton regulation. This supports the role of selective autophagy as a central plant immune mechanism and will permit to decipher its precise regulation in response to phytopathogenic bacteria.
