title: Molecular functions of Xanthomonas type III effector AvrBsT and its plant interactors in cell death and defense signaling.
abstract: Xanthomonas effector AvrBsT interacts with plant defense proteins and triggers cell death and defense response. This review highlights our current understanding of the molecular functions of AvrBsT and its host interactor proteins. The AvrBsT protein is a member of a growing family of effector proteins in both plant and animal pathogens. Xanthomonas type III effector AvrBsT, a member of the YopJ/AvrRxv family, suppresses plant defense responses in susceptible hosts, but triggers cell death signaling leading to hypersensitive response (HR) and defense responses in resistant plants. AvrBsT interacts with host defense-related proteins to trigger the HR cell death and defense responses in plants. Here, we review and discuss recent progress in understanding the molecular functions of AvrBsT and its host interactor proteins in pepper (Capsicum annuum). Pepper arginine decarboxylase1 (CaADC1), pepper aldehyde dehydrogenase1 (CaALDH1), pepper heat shock protein 70a (CaHSP70a), pepper suppressor of the G2 allele of skp1 (CaSGT1), pepper SNF1-related kinase1 (SnRK1), and Arabidopsis acetylated interacting protein1 (ACIP1) have been identified as AvrBsT interactors in pepper and Arabidopsis. Gene expression profiling, virus-induced gene silencing, and transient transgenic overexpression approaches have advanced the functional characterization of AvrBsT-interacting proteins in plants. AvrBsT is localized in the cytoplasm and forms protein-protein complexes with host interactors. All identified AvrBsT interactors regulate HR cell death and defense responses in plants. Notably, CaSGT1 physically binds to both AvrBsT and pepper receptor-like cytoplasmic kinase1 (CaPIK1) in the cytoplasm. During infection with Xanthomonas campestris pv. vesicatoria strain Ds1 (avrBsT), AvrBsT is phosphorylated by CaPIK1 and forms the active AvrBsT-CaSGT1-CaPIK1 complex, which ultimately triggers HR cell death and defense responses. Collectively, the AvrBsT interactor proteins are involved in plant cell death and immunity signaling.
authors.affiliation: Department of Integrative Plant Science, Chung-Ang University, Anseong, 17546, Republic of Korea.
authors.forename: Sang Wook
authors.initials: SW
authors.lastname: Han
authors.affiliation: Laboratory of Molecular Plant Pathology, College of Life Sciences and Biotechnology, Korea University, Anam-dong, Sungbuk-ku, Seoul, 02841, Republic of Korea. bkhwang@korea.ac.kr.
authors.forename: Byung Kook
authors.identifier: http://orcid.org/0000-0003-1782-8990
authors.initials: BK
authors.lastname: Hwang
mesh_terms: D000444:Aldehyde Dehydrogenase / Q000235:genetics / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002212:Capsicum / Q000378:metabolism / Q000382:microbiology*; D002262:Carboxy-Lyases / Q000235:genetics / Q000378:metabolism; D016923:Cell Death; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism; D054884:Host-Pathogen Interactions; D059828:Plant Cells / Q000378:metabolism / Q000382:microbiology*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D016959:Xanthomonas campestris / Q000378:metabolism / Q000472:pathogenicity* / Q000502:physiology
chemical_list: D001426:Bacterial Proteins; D018840:HSP70 Heat-Shock Proteins; D010940:Plant Proteins; D000444:Aldehyde Dehydrogenase; D002262:Carboxy-Lyases; C019722:arginine decarboxylase
keywords: AvrBsT interactors; Cell death; Defense-related genes; Hypersensitive response; Plant defense; Xanthomonas type III effector AvrBsT