title: Implications of terminal oxidase function in regulation of salicylic acid on soybean seedling photosynthetic performance under water stress.
abstract: The aim of this study is to investigate whether exogenous application of salicylic acid (SA) could modulate the photosynthetic capacity of soybean seedlings in water stress tolerance, and to clarify the potential functions of terminal oxidase (plastid terminal oxidase (PTOX) and alternative oxidase (AOX)) in SA' s regulation on photosynthesis. The effects of SA and water stress on gas exchange, pigment contents, chlorophyll fluorescence, enzymes (guaiacol peroxidase (POD; EC 1.11.1.7), superoxide dismutase (SOD; EC 1.15.1.1), catalase (CAT; EC 1.11.1.6), ascorbate peroxidase (APX; EC 1.11.1.11) and NADP-malate dehydrogenase (NADP-MDH; EC1.1.1.82)) activity and transcript levels of PTOX, AOX1, AOX2a, AOX2b were examined in a hydroponic cultivation system. Results indicate that water stress significantly decreased the photosynthetic rate (Pn), stomatal conductance (Gs), transpiration rate (E), pigment contents (Chla + b, Chla/b, Car), maximum quantum yield of PSⅡphotochemistry (Fv/Fm), efficiency of excitation capture of open PSⅡcenter (Fv'/Fm'), quantum efficiency of PSⅡphotochemistry (ΦPSⅡ), photochemical quenching (qP), and increased malondialdehyde (MDA) content and the activity of all the enzymes. SA pretreatment led to significant decreases in Ci and MDA content, and increases in Pn, Gs, E, pigment contents, Fv/Fm, Fv'/Fm', ΦPSⅡ, qP, and the activity of all the enzymes. SA treatment and water stress alone significantly up-regulated the expression of PTOX, AOX1 and AOX2b. SA pretreatment further increased the transcript levels of PTOX and AOX2b of soybean seedling under water stress. These results indicate that SA application alleviates the water stress-induced decrease in photosynthesis may mainly through maintaining a lower reactive oxygen species (ROS) level, a greater PSⅡefficiency, and an enhanced alternative respiration and chlororespiration. PTOX and AOX may play important roles in SA-mediated resistance to water stress.
authors.affiliation: College of Agronomy, Sichuan Agricultural University, No.211, Huimin Road, Gongping Town, Wenjiang District, Chengdu, 611130, Sichuan, China; Agrotechnical Extension Station, Agricultural Bureau of Dazhou City, No.52, Heye Street, Tongchuan District, Dazhou, 635000, Sichuan, China. Electronic address: typing897@163.com.
authors.forename: Yanping
authors.initials: Y
authors.lastname: Tang
authors.affiliation: College of Agronomy, Sichuan Agricultural University, No.211, Huimin Road, Gongping Town, Wenjiang District, Chengdu, 611130, Sichuan, China. Electronic address: sunxin529@163.com.
authors.forename: Xin
authors.initials: X
authors.lastname: Sun
authors.affiliation: College of Agronomy, Sichuan Agricultural University, No.211, Huimin Road, Gongping Town, Wenjiang District, Chengdu, 611130, Sichuan, China. Electronic address: wtlst@163.com.
authors.forename: Tao
authors.initials: T
authors.lastname: Wen
authors.affiliation: College of Agronomy, Sichuan Agricultural University, No.211, Huimin Road, Gongping Town, Wenjiang District, Chengdu, 611130, Sichuan, China.
authors.forename: Mingjie
authors.initials: M
authors.lastname: Liu
authors.affiliation: College of Agronomy, Sichuan Agricultural University, No.211, Huimin Road, Gongping Town, Wenjiang District, Chengdu, 611130, Sichuan, China.
authors.forename: Mingyan
authors.initials: M
authors.lastname: Yang
authors.affiliation: College of Agronomy, Sichuan Agricultural University, No.211, Huimin Road, Gongping Town, Wenjiang District, Chengdu, 611130, Sichuan, China.
authors.forename: Xuefei
authors.initials: X
authors.lastname: Chen
mesh_terms: D000975:Antioxidants / Q000378:metabolism; D003681:Dehydration; D005453:Fluorescence; D005740:Gases / Q000378:metabolism; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D008291:Malate Dehydrogenase / Q000378:metabolism; D009249:NADP / Q000378:metabolism; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000378:metabolism*; D010788:Photosynthesis / Q000187:drug effects*; D010860:Pigments, Biological / Q000378:metabolism; D010940:Plant Proteins / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction; D020156:Salicylic Acid / Q000494:pharmacology*; D036226:Seedlings / Q000187:drug effects / Q000502:physiology*; D013025:Glycine max / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics / Q000502:physiology*
chemical_list: D000975:Antioxidants; D005740:Gases; D010860:Pigments, Biological; D010940:Plant Proteins; D012333:RNA, Messenger; D009249:NADP; D010088:Oxidoreductases; D008291:Malate Dehydrogenase; D020156:Salicylic Acid
keywords: Photosynthesis; Salicylic acid; Soybean; Terminal oxidase; Water stress