title: Effects of salicylic acid on alternative pathway respiration and alternative oxidase expression in tobacco calli.
abstract: The alternative pathway (AP) respiration of plants is a cyanide-resistant and non-phosphorylating electron transport pathway in mitochondria. Alternative oxidase (AOX) is the terminal oxidase of the AP and exists in plant mitochondria as two states: the reduced, noncovalently linked state or the oxidized, covalently cross-linked state. In the present study, the effects of 20 microM exogenous salicylic acid (SA) on both AP activity and AOX expression in mitochondria of tobacco (Nicotiana rustica L. cv. yellow flower) calli were investigated. The results showed that SA treatment enhanced the AP activity. During the process of SA treatment, the AP activity increased dramatically and achieved the peak value after 8 h of treatment. Then it declined until 16 h, and maintained a steady level between 16 and 24 h. Changes in both the total AOX protein level and the reduced state were in accordance with the AP activity, but the oxidized state changed differently. The aox1 gene transcript level also showed a similar change as the AP activity and AOX protein level. The induction of AOX expression by low concentrations of SA was inferred through a reactive oxygen species (ROS)-independent pathway. These results indicate that the enhancement of AP activity in response to SA is correlated to the expression of AOX, and the reduced, non-covalently linked state of AOX plays an important role during this process.
authors.affiliation: Key Laboratory of Bio-resources and Eco-environment (Ministry of Education), College of Life Sciences, Sichuan University, Chengdu 610064, Sichuan, PR China.
authors.forename: Tao
authors.initials: T
authors.lastname: Lei
authors.forename: Ying-Cai
authors.initials: YC
authors.lastname: Yan
authors.forename: De-Hui
authors.initials: DH
authors.lastname: Xi
authors.forename: Hong
authors.initials: H
authors.lastname: Feng
authors.forename: Xin
authors.initials: X
authors.lastname: Sun
authors.forename: Fan
authors.initials: F
authors.lastname: Zhang
authors.forename: Wei-Lin
authors.initials: WL
authors.lastname: Xu
authors.forename: Hou-Guo
authors.initials: HG
authors.lastname: Liang
authors.forename: Hong-Hui
authors.initials: HH
authors.lastname: Lin
mesh_terms: D019069:Cell Respiration / Q000187:drug effects; D017931:DNA Primers; D004579:Electron Transport / Q000187:drug effects; D008928:Mitochondria / Q000201:enzymology; D024101:Mitochondrial Proteins; D010088:Oxidoreductases / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D018515:Plant Leaves; D010940:Plant Proteins; D016133:Polymerase Chain Reaction; D018749:RNA, Plant / Q000235:genetics; D020156:Salicylic Acid / Q000494:pharmacology*; D036226:Seedlings; D014026:Nicotiana / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D000099188:Alternative Oxidase
chemical_list: D017931:DNA Primers; D024101:Mitochondrial Proteins; D010088:Oxidoreductases; D010940:Plant Proteins; D018749:RNA, Plant; D020156:Salicylic Acid; D000099188:Alternative Oxidase