title: NADPH oxidase inhibitor diphenyleneiodonium and reduced glutathione mitigate ethephon-mediated leaf senescence, H2O2 elevation and senescence-associated gene expression in sweet potato (Ipomoea batatas).
abstract: Ethephon, an ethylene releasing compound, promoted leaf senescence, H2O2 elevation, and senescence-associated gene expression in sweet potato. It also affected the glutathione and ascorbate levels, which in turn perturbed H2O2 homeostasis. The decrease of reduced glutathione and the accumulation of dehydroascorbate correlated with leaf senescence and H2O2 elevation at 72h in ethephon-treated leaves. Exogenous application of reduced glutathione caused quicker and significant increase of its intracellular level and resulted in the attenuation of leaf senescence and H2O2 elevation. A small H2O2 peak produced within the first 4h after ethephon application was also eliminated by reduced glutathione. Diphenyleneiodonium (DPI), an NADPH oxidase inhibitor, delayed leaf senescence and H2O2 elevation at 72h, and its influence was effective only within the first 4h after ethephon treatment. Ethephon-induced senescence-associated gene expression was repressed by DPI and reduced glutathione at 72h in pretreated leaves. Leaves treated with l-buthionine sulfoximine, an endogenous glutathione synthetase inhibitor, did enhance senescence-associated gene expression, and the activation was strongly repressed by reduced glutathione. In conclusion, ethephon-mediated leaf senescence, H2O2 elevation and senescence-associated gene expression are all alleviated by reduced glutathione and NADPH oxidase inhibitor DPI. The speed and the amount of intracellular reduced glutathione accumulation influence its effectiveness of protection against ethephon-mediated effects. Reactive oxygen species generated from NADPH oxidase likely serves as an oxidative stress signal and participates in ethephon signaling. The possible roles of NADPH oxidase and reduced glutathione in the regulation of oxidative stress signal in ethephon are discussed.
authors.affiliation: Department of Biological Sciences, National Sun Yat-sen University, 804 Kaohsiung, Taiwan. Electronic address: hjchen@faculty.nsysu.edu.tw.
authors.forename: Hsien-Jung
authors.initials: HJ
authors.lastname: Chen
authors.forename: Chin-Shu
authors.initials: CS
authors.lastname: Huang
authors.forename: Guan-Jhong
authors.initials: GJ
authors.lastname: Huang
authors.forename: Te-Jin
authors.initials: TJ
authors.lastname: Chow
authors.forename: Yaw-Huei
authors.initials: YH
authors.lastname: Lin
mesh_terms: D001205:Ascorbic Acid / Q000378:metabolism; D019328:Buthionine Sulfoximine / Q000494:pharmacology; D016922:Cellular Senescence; D002734:Chlorophyll / Q000378:metabolism; D005030:Ethylenes / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D005978:Glutathione / Q000378:metabolism*; D006861:Hydrogen Peroxide / Q000378:metabolism*; D027723:Ipomoea batatas / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D019255:NADPH Oxidases / Q000037:antagonists & inhibitors*; D009861:Onium Compounds / Q000494:pharmacology*; D009943:Organophosphorus Compounds / Q000494:pharmacology*; D018515:Plant Leaves / Q000166:cytology / Q000187:drug effects / Q000378:metabolism
chemical_list: D005030:Ethylenes; D009861:Onium Compounds; D009943:Organophosphorus Compounds; D002734:Chlorophyll; D019328:Buthionine Sulfoximine; C007517:diphenyleneiodonium; C036216:ethylene; D006861:Hydrogen Peroxide; D019255:NADPH Oxidases; D005978:Glutathione; D001205:Ascorbic Acid; C005073:ethephon
keywords: 2-(N-morpholino)-ethane sulphonic acid; CCI; DAB; DPI; Ethephon; Leaf senescence; MES; NADPH oxidase; RT-PCR; Reduced glutathione; Sweet potato; chlorophyll content index; diaminobenzidine; diphenyleneiodonium; reverse transcription-polymerase chain reaction