title: Involvement of the pepper antimicrobial protein CaAMP1 gene in broad spectrum disease resistance.
abstract: Pathogen-inducible antimicrobial defense-related proteins have emerged as key antibiotic peptides and enzymes involved in disease resistance in plants. A novel antimicrobial protein gene, CaAMP1 (for Capsicum annuum ANTIMICROBIAL PROTEIN1), was isolated from pepper (C. annuum) leaves infected with Xanthomonas campestris pv vesicatoria. Expression of the CaAMP1 gene was strongly induced in pepper leaves not only during pathogen infection but also after exposure to abiotic elicitors. The purified recombinant CaAMP1 protein possessed broad-spectrum antimicrobial activity against phytopathogenic bacteria and fungi. CaAMP1:smGFP fusion protein was localized mainly in the external and intercellular regions of onion (Allium cepa) epidermal cells. The virus-induced gene silencing technique and gain-of-function transgenic plants were used to determine the CaAMP1 gene function in plant defense. Silencing of CaAMP1 led to enhanced susceptibility to X. campestris pv vesicatoria and Colletotrichum coccodes infection, accompanied by reduced PATHOGENESIS-RELATED (PR) gene expression. In contrast, overexpression of CaAMP1 in Arabidopsis (Arabidopsis thaliana) conferred broad-spectrum resistance to the hemibiotrophic bacterial pathogen Pseudomonas syringae pv tomato, the biotrophic oomycete Hyaloperonospora parasitica, and the fungal necrotrophic pathogens Fusarium oxysporum f. sp. matthiolae and Alternaria brassicicola. CaAMP1 overexpression induced the salicylic acid pathway-dependent genes PR1 and PR5 but not the jasmonic acid-dependent defense gene PDF1.2 during P. syringae pv tomato infection. Together, these results suggest that the antimicrobial CaAMP1 protein is involved in broad-spectrum resistance to bacterial and fungal pathogen infection.
authors.affiliation: Laboratory of Molecular Plant Pathology, School of Life Sciences and Biotechnology, Korea University, Seoul, Republic of Korea.
authors.forename: Sung Chul
authors.initials: SC
authors.lastname: Lee
authors.forename: In Sun
authors.initials: IS
authors.lastname: Hwang
authors.forename: Hyong Woo
authors.initials: HW
authors.lastname: Choi
authors.forename: Byung Kook
authors.initials: BK
authors.lastname: Hwang
mesh_terms: D000595:Amino Acid Sequence; D002212:Capsicum / Q000235:genetics* / Q000378:metabolism / Q000382:microbiology*; D005658:Fungi / Q000502:physiology; D020868:Gene Silencing; D017343:Genes, Plant; D008969:Molecular Sequence Data; D010935:Plant Diseases / Q000235:genetics* / Q000276:immunology; D018515:Plant Leaves / Q000235:genetics / Q000378:metabolism / Q000382:microbiology; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000235:genetics / Q000378:metabolism / Q000382:microbiology; D018749:RNA, Plant / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D014170:Transformation, Genetic; D016959:Xanthomonas campestris / Q000502:physiology
chemical_list: D010940:Plant Proteins; D018749:RNA, Plant; D011993:Recombinant Fusion Proteins