title: Contribution of the Alternative Respiratory Pathway to PSII Photoprotection in C3 and C4 Plants.
abstract: The mechanism by which the mitochondrial alternative oxidase (AOX) pathway contributes to photosystem II (PSII) photoprotection is in dispute. It was generally thought that the AOX pathway protects photosystems by dissipating excess reducing equivalents exported from chloroplasts through the malate/oxaloacetate (Mal/OAA) shuttle and thus preventing the over-reduction of chloroplasts. In this study, using the aox1a Arabidopsis mutant and nine other C3 and C4 plant species, we revealed an additional action model of the AOX pathway in PSII photoprotection. Although the AOX pathway contributes to PSII photoprotection in C3 leaves treated with high light, this contribution was observed to disappear when photorespiration was suppressed. Disruption or inhibition of the AOX pathway significantly decreased the photorespiration in C3 leaves. Moreover, the AOX pathway did not respond to high light and contributed little to PSII photoprotection in C4 leaves possessing a highly active Mal/OAA shuttle but with little photorespiration. These results demonstrate that the AOX pathway contributes to PSII photoprotection in C3 plants by maintaining photorespiration to detoxify glycolate and via the indirect export of excess reducing equivalents from chloroplasts by the Mal/OAA shuttle. This new action model explains why the AOX pathway does not contribute to PSII photoprotection in C4 plants.
authors.affiliation: State Key Laboratory of Crop Biology, Shandong Agricultural University, Tai'an 271018, China; College of Life Sciences, Shandong Agricultural University, Tai'an 271018, China; College of Horticulture Science and Engineering, Shandong Agricultural University, Tai'an 271018, China.
authors.forename: Zi-Shan
authors.initials: ZS
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Crop Biology, Shandong Agricultural University, Tai'an 271018, China; College of Life Sciences, Shandong Agricultural University, Tai'an 271018, China.
authors.forename: Mei-Jun
authors.initials: MJ
authors.lastname: Liu
authors.affiliation: Department of Plant Physiology, FB5, University of Osnabrueck, 49069 Osnabrueck, Germany.
authors.forename: Renate
authors.initials: R
authors.lastname: Scheibe
authors.affiliation: Department of Plant Physiology, FB5, University of Osnabrueck, 49069 Osnabrueck, Germany.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Selinski
authors.affiliation: State Key Laboratory of Crop Biology, Shandong Agricultural University, Tai'an 271018, China; College of Life Sciences, Shandong Agricultural University, Tai'an 271018, China; National and Local Joint Engineering Laboratory of Ecological Mariculture, Institute of Oceanology, Chinese Academy of Sciences, 7 Nanhai Road, Qingdao 266071, China.
authors.forename: Li-Tao
authors.initials: LT
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Crop Biology, Shandong Agricultural University, Tai'an 271018, China; College of Life Sciences, Shandong Agricultural University, Tai'an 271018, China; Wheat Research Institute, Henan Academy of Agricultural Sciences, Zhengzhou, Henan 450002, China.
authors.forename: Cheng
authors.initials: C
authors.lastname: Yang
authors.affiliation: State Key Laboratory of Crop Biology, Shandong Agricultural University, Tai'an 271018, China; College of Life Sciences, Shandong Agricultural University, Tai'an 271018, China.
authors.forename: Xiang-Long
authors.initials: XL
authors.lastname: Meng
authors.affiliation: State Key Laboratory of Crop Biology, Shandong Agricultural University, Tai'an 271018, China; College of Life Sciences, Shandong Agricultural University, Tai'an 271018, China. Electronic address: gaohy@sdau.edu.cn.
authors.forename: Hui-Yuan
authors.initials: HY
authors.lastname: Gao
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism* / Q000528:radiation effects; D004579:Electron Transport; D008027:Light; D053858:Metabolic Networks and Pathways; D024101:Mitochondrial Proteins / Q000235:genetics / Q000378:metabolism*; D008954:Models, Biological; D009154:Mutation; D010088:Oxidoreductases / Q000235:genetics / Q000378:metabolism*; D045332:Photosystem II Protein Complex / Q000235:genetics / Q000378:metabolism*; D018515:Plant Leaves / Q000378:metabolism / Q000528:radiation effects; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D000099188:Alternative Oxidase
chemical_list: D024101:Mitochondrial Proteins; D010088:Oxidoreductases; D045332:Photosystem II Protein Complex; D010940:Plant Proteins; D000099188:Alternative Oxidase
keywords: C3 plant; C4 plant; alternative oxidase; photoprotection; photorespiration; photosystem II