title: Pepper heat shock protein 70a interacts with the type III effector AvrBsT and triggers plant cell death and immunity.
abstract: Heat shock proteins (HSPs) function as molecular chaperones and are essential for the maintenance and/or restoration of protein homeostasis. The genus Xanthomonas type III effector protein AvrBsT induces hypersensitive cell death in pepper (Capsicum annuum). Here, we report the identification of the pepper CaHSP70a as an AvrBsT-interacting protein. Bimolecular fluorescence complementation and coimmunoprecipitation assays confirm the specific interaction between CaHSP70a and AvrBsT in planta. The CaHSP70a peptide-binding domain is essential for its interaction with AvrBsT. Heat stress (37°C) and Xanthomonas campestris pv vesicatoria (Xcv) infection distinctly induce CaHSP70a in pepper leaves. Cytoplasmic CaHSP70a proteins significantly accumulate in pepper leaves to induce the hypersensitive cell death response by Xcv (avrBsT) infection. Transient CaHSP70a overexpression induces hypersensitive cell death under heat stress, which is accompanied by strong induction of defense- and cell death-related genes. The CaHSP70a peptide-binding domain and ATPase-binding domain are required to trigger cell death under heat stress. Transient coexpression of CaHSP70a and avrBsT leads to cytoplasmic localization of the CaHSP70a-AvrBsT complex and significantly enhances avrBsT-triggered cell death in Nicotiana benthamiana. CaHSP70a silencing in pepper enhances Xcv growth but disrupts the reactive oxygen species burst and cell death response during Xcv infection. Expression of some defense marker genes is significantly reduced in CaHSP70a-silenced leaves, with lower levels of the defense hormones salicylic acid and jasmonic acid. Together, these results suggest that CaHSP70a interacts with the type III effector AvrBsT and is required for cell death and immunity in plants.
authors.affiliation: Laboratory of Molecular Plant Pathology, College of Life Sciences and Biotechnology, Korea University, Seoul 136-713, Republic of Korea.
authors.forename: Nak Hyun
authors.initials: NH
authors.lastname: Kim
authors.affiliation: Laboratory of Molecular Plant Pathology, College of Life Sciences and Biotechnology, Korea University, Seoul 136-713, Republic of Korea bkhwang@korea.ac.kr.
authors.forename: Byung Kook
authors.initials: BK
authors.lastname: Hwang
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism*; D058947:Bacterial Secretion Systems; D002212:Capsicum / Q000166:cytology* / Q000235:genetics / Q000276:immunology* / Q000382:microbiology; D016923:Cell Death; D003517:Cyclopentanes / Q000378:metabolism; D060467:Disease Resistance / Q000276:immunology; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant; D020868:Gene Silencing; D017343:Genes, Plant; D018840:HSP70 Heat-Shock Proteins / Q000737:chemistry / Q000378:metabolism*; D018869:Heat-Shock Response; D054883:Oxylipins / Q000378:metabolism; D059828:Plant Cells / Q000378:metabolism*; D010935:Plant Diseases / Q000276:immunology / Q000382:microbiology; D057865:Plant Immunity; D018515:Plant Leaves / Q000166:cytology / Q000378:metabolism / Q000382:microbiology; D010940:Plant Proteins / Q000737:chemistry / Q000378:metabolism*; D030821:Plants, Genetically Modified; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D017382:Reactive Oxygen Species / Q000378:metabolism; D020156:Salicylic Acid / Q000378:metabolism; D017384:Sequence Deletion; D013347:Subcellular Fractions / Q000378:metabolism; D020798:Two-Hybrid System Techniques; D016959:Xanthomonas campestris / Q000502:physiology
chemical_list: D001426:Bacterial Proteins; D058947:Bacterial Secretion Systems; D003517:Cyclopentanes; D018840:HSP70 Heat-Shock Proteins; D054883:Oxylipins; D010940:Plant Proteins; D017382:Reactive Oxygen Species; C011006:jasmonic acid; D020156:Salicylic Acid