title: Sweet potato calmodulin SPCAM is involved in salt stress-mediated leaf senescence, H₂O₂ elevation and senescence-associated gene expression.
abstract: The sweet potato calmodulin gene, SPCAM, was previously cloned and shown to participate in ethephon-mediated leaf senescence, H₂O₂ elevation and senescence-associated gene expression. In this report, an association of SPCAM with NaCl stress is reported. Expression of SPCAM was significantly enhanced by NaCl on days 1 and 2 after salt treatment in a dose-dependent manner and drastically decreased again on the third day. Starting on day 6, salt stress also remarkably promoted leaf senescence, H₂O₂ elevation and senescence-associated gene expression in a dose-dependent manner. These salt stress-mediated effects were strongly inhibited by chlorpromazine, a calmodulin inhibitor, and the chlorpromazine-induced repression could be reversed by exogenous application of purified calmodulin fusion protein. These data suggest an involvement of calmodulin in salt stress-mediated leaf senescence, H₂O₂ elevation and senescence-associated gene expression in sweet potato. Exogenous application of SPCAM fusion protein alone, however, did not significantly accelerate leaf senescence and senescence-associated gene expression, but only showed a slight effect 12 days after treatment. These data suggest that additional components are involved in salt stress-mediated leaf senescence in sweet potato, possibly induced by and coordinated with SPCAM. In conclusion, the sweet potato calmodulin gene is NaCl-inducible and participates in salt stress-mediated leaf senescence, H₂O₂ elevation and senescence-associated gene expression.
authors.affiliation: Department of Biological Sciences, National Sun Yat-sen University, 804 Kaohsiung, Taiwan. hjchen@faculty.nsysu.edu.tw
authors.forename: Hsien-Jung
authors.initials: HJ
authors.lastname: Chen
authors.forename: Zhe-Wei
authors.initials: ZW
authors.lastname: Lin
authors.forename: Guan-Jhong
authors.initials: GJ
authors.lastname: Huang
authors.forename: Yaw-Huei
authors.initials: YH
authors.lastname: Lin
mesh_terms: D002147:Calmodulin / Q000037:antagonists & inhibitors / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D002734:Chlorophyll / Q000378:metabolism; D002746:Chlorpromazine / Q000494:pharmacology*; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression; D018506:Gene Expression Regulation, Plant; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D027723:Ipomoea batatas / Q000033:anatomy & histology / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D016877:Oxidants / Q000494:pharmacology*; D018515:Plant Leaves / Q000033:anatomy & histology / Q000187:drug effects / Q000235:genetics / Q000502:physiology; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins; D012965:Sodium Chloride / Q000494:pharmacology*
chemical_list: D002147:Calmodulin; D016877:Oxidants; D010940:Plant Proteins; D011993:Recombinant Fusion Proteins; D002734:Chlorophyll; D012965:Sodium Chloride; D006861:Hydrogen Peroxide; D002746:Chlorpromazine