title: Glutathione-dependent induction of local and systemic defense against oxidative stress by exogenous melatonin in cucumber (Cucumis sativus L.).
abstract: Melatonin is involved in defending against oxidative stress caused by various environmental stresses in plants. In this study, the roles of exogenous melatonin in regulating local and systemic defense against photooxidative stress in cucumber (Cucumis sativus) and the involvement of redox signaling were examined. Foliar or rhizospheric treatment with melatonin enhanced tolerance to photooxidative stress in both melatonin-treated leaves and untreated systemic leaves. Increased melatonin levels are capable of increasing glutathione (reduced glutathione [GSH]) redox status. Application of H2 O2 and GSH also induced tolerance to photooxidative stress, while inhibition of H2 O2 accumulation and GSH synthesis compromised melatonin-induced local and systemic tolerance to photooxidative stress. H2 O2 treatment increased the GSH/oxidized glutathione (GSSG) ratio, while inhibition of H2 O2 accumulation prevented a melatonin-induced increase in the GSH/GSSG ratio. Additionally, inhibition of GSH synthesis blocked H2 O2 -induced photooxidative stress tolerance, whereas scavenging or inhibition of H2 O2 production attenuated but did not abolish GSH-induced tolerance to photooxidative stress. These results strongly suggest that exogenous melatonin is capable of inducing both local and systemic defense against photooxidative stress and melatonin-enhanced GSH/GSSG ratio in a H2 O2 -dependent manner is critical in the induction of tolerance.
authors.affiliation: Department of Horticulture, Northwest A&F University, Shaanxi, China.
authors.forename: Hao
authors.initials: H
authors.lastname: Li
authors.affiliation: Department of Horticulture, Northwest A&F University, Shaanxi, China.
authors.forename: Jie
authors.initials: J
authors.lastname: He
authors.affiliation: Department of Horticulture, Northwest A&F University, Shaanxi, China.
authors.forename: Xiaozhen
authors.initials: X
authors.lastname: Yang
authors.affiliation: Key Laboratory of Tea Biology and Resources Utilization, Tea Research Institute, Chinese Academy of Agricultural Sciences, Ministry of Agriculture, Zhejiang, China.
authors.forename: Xin
authors.initials: X
authors.lastname: Li
authors.affiliation: Department of Horticulture, Northwest A&F University, Shaanxi, China.
authors.forename: Dan
authors.initials: D
authors.lastname: Luo
authors.affiliation: Department of Horticulture, Northwest A&F University, Shaanxi, China.
authors.forename: Chunhua
authors.initials: C
authors.lastname: Wei
authors.affiliation: Department of Horticulture, Northwest A&F University, Shaanxi, China.
authors.forename: Jianxiang
authors.initials: J
authors.lastname: Ma
authors.affiliation: Department of Horticulture, Northwest A&F University, Shaanxi, China.
authors.forename: Yong
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Department of Horticulture, Northwest A&F University, Shaanxi, China.
authors.forename: Jianqiang
authors.initials: J
authors.lastname: Yang
authors.affiliation: Department of Horticulture, Northwest A&F University, Shaanxi, China.
authors.forename: Xian
authors.initials: X
authors.lastname: Zhang
mesh_terms: D018553:Cucumis sativus / Q000378:metabolism*; D005978:Glutathione / Q000378:metabolism*; D008550:Melatonin / Q000494:pharmacology*; D018384:Oxidative Stress / Q000187:drug effects*
chemical_list: D005978:Glutathione; D008550:Melatonin
keywords: Cucumis sativus; glutathione; hydrogen peroxide; local/systemic defense; melatonin