title: The pepper calmodulin gene CaCaM1 is involved in reactive oxygen species and nitric oxide generation required for cell death and the defense response.
abstract: Calcium signaling has emerged as an important signal transduction pathway of higher plants in response to biotic and abiotic stresses. Ca2+-bound calmodulin (CaM) plays a critical role in decoding and transducing stress signals by activating specific targets. Here, we isolated and functionally characterized the pathogen-responsive CaM gene, Capsicum annuum calmodulin 1 (CaCaM1), from pepper (C. annuum) plants. The cellular function of CaCaM1 was verified by Agrobacterium spp.-mediated transient expression in pepper and transgenic overexpression in Arabidopsis thaliana. Agrobacterium spp.-mediated transient expression of CaCaM1 activated reactive oxygen species (ROS), nitric oxide (NO) generation, and hypersensitive response (HR)-like cell death in pepper leaves, ultimately leading to local acquired resistance to Xanthomonas campestris pv. vesicatoria. CaCaM1-overexpression (OX) Arabidopsis exhibited enhanced resistance to Pseudomonas syringae and Hyaloperonospora parasitica, which was accompanied by enhanced ROS and NO generation and HR-like cell death. Treatment with the calcium-channel blocker suppressed the oxidative and NO bursts and HR-like cell death that were triggered by CaCaM1 expression in pepper and Arabidopsis, suggesting that calcium influx is required for the activation of CaCaM1-mediated defense responses in plants. Upon treatment with the CaM antagonist, virulent P. syringae pv. tomato-induced NO generation was also compromised in CaCaM1-OX leaves. Together, these results suggest that the CaCaM1 gene functions in ROS and NO generation are essential for cell death and defense responses in plants.
authors.affiliation: Laboratory of Molecular Plant Pathology, School of Life Sciences and Biotechnology, Korea University, Anam-dong, Sungbuk-ku, Seoul 136-713, Republic of Korea.
authors.forename: Hyong Woo
authors.initials: HW
authors.lastname: Choi
authors.forename: Dong Hyuk
authors.initials: DH
authors.lastname: Lee
authors.forename: Byung Kook
authors.initials: BK
authors.lastname: Hwang
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism; D020013:Calcium Signaling / Q000502:physiology; D002212:Capsicum / Q000235:genetics*; D016923:Cell Death / Q000502:physiology*; D018506:Gene Expression Regulation, Plant / Q000502:physiology*; D017343:Genes, Plant; D008969:Molecular Sequence Data; D009569:Nitric Oxide / Q000096:biosynthesis*; D010935:Plant Diseases / Q000235:genetics; D018515:Plant Leaves; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D030821:Plants, Genetically Modified; D017382:Reactive Oxygen Species / Q000378:metabolism*; D012231:Rhizobium; D016959:Xanthomonas campestris
chemical_list: D010940:Plant Proteins; D017382:Reactive Oxygen Species; D009569:Nitric Oxide