title: Physiological role of AOX1a in photosynthesis and maintenance of cellular redox homeostasis under high light in Arabidopsis thaliana.
abstract: As plants are sessile, they often face high light (HL) stress that causes damage of the photosynthetic machinery leading to decreased photosynthesis. The importance of alternative oxidase (AOX) in optimizing photosynthesis is well documented. In the present study, the role of AOX in sustaining photosynthesis under HL was studied using AOX1a knockout mutants (aox1a) of Arabidopsis thaliana. Under growth light (GL; 50 μmol photons m(-2) s(-1)) conditions, aox1a plants did not show any changes in photosynthetic parameters, NAD(P)/H redox ratios, or respiratory O2 uptake when compared to wild-type (WT). Upon exposure to HL (700 μmol photons m(-2) s(-1)), respiratory rates did not vary between WT and aox1a. But, photosynthetic parameters related to photosystem II (PSII) and NaHCO3 dependent O2 evolution decreased, while the P700 reduction state increased in aox1a compared to WT. Further, under HL, the redox state of cellular NAD(P)/H pools increased with concomitant rise in reactive oxygen species (ROS) and malondialdehyde (MDA) content in aox1a compared to WT. In presence of HL, the transcript levels of several genes related to antioxidant, malate-oxaloacetate (malate-OAA) shuttle, photorespiratory and respiratory enzymes was higher in aox1a compared to WT. Taken together, these results demonstrate that under HL, in spite of significant increase in transcript levels of several genes mentioned above to maintain cellular redox homeostasis and minimize ROS production, Arabidopsis plants deficient in AOX1a were unable to sustain photosynthesis as is the case in WT plants.
authors.affiliation: Department of Plant Sciences, School of Life Sciences, Centre for Advanced Studies, University of Hyderabad, Hyderabad 500 046, India.
authors.forename: Abhaypratap
authors.initials: A
authors.lastname: Vishwakarma
authors.affiliation: Genomics Facility, University of Hyderabad, Hyderabad 500 046, India.
authors.forename: Leena
authors.initials: L
authors.lastname: Bashyam
authors.affiliation: Department of Animal Sciences, School of Life Sciences, Centre for Advanced Studies, University of Hyderabad, Hyderabad 500 046, India.
authors.forename: Balasubramanian
authors.initials: B
authors.lastname: Senthilkumaran
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 Sciences, School of Life Sciences, Centre for Advanced Studies, University of Hyderabad, Hyderabad 500 046, India; Department of Plant Physiology, FB5, University of Osnabrueck, 49069 Osnabrueck, Germany; Department of Biotechnology and Bioinformatics, School of Life Sciences, Centre for Advanced Studies, University of Hyderabad, Hyderabad 500 046, India. Electronic address: kpssl@uohyd.ac.in.
authors.forename: Kollipara
authors.initials: K
authors.lastname: Padmasree
mesh_terms: D000975:Antioxidants / Q000378:metabolism; D017360:Arabidopsis / Q000201:enzymology / Q000235:genetics / Q000502:physiology* / Q000528:radiation effects; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D019069:Cell Respiration; D002734:Chlorophyll / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D006706:Homeostasis; D008027:Light; D015227:Lipid Peroxidation; D008293:Malates / Q000378:metabolism; D008315:Malondialdehyde / Q000378:metabolism; D024101:Mitochondrial Proteins / Q000235:genetics / Q000378:metabolism*; D062907:Oxaloacetic Acid / Q000378:metabolism; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000235:genetics / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism*; D010788:Photosynthesis; D045332:Photosystem II Protein Complex / Q000235:genetics / Q000378:metabolism; D018515:Plant Leaves / Q000201:enzymology / Q000235:genetics / Q000502:physiology / Q000528:radiation effects; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D017382:Reactive Oxygen Species / Q000378:metabolism; D013312:Stress, Physiological; D000099188:Alternative Oxidase
chemical_list: D000975:Antioxidants; D029681:Arabidopsis Proteins; D002734:Chlorophyll; D008293:Malates; D008315:Malondialdehyde; D024101:Mitochondrial Proteins; D062907:Oxaloacetic Acid; D010088:Oxidoreductases; D010100:Oxygen; D045332:Photosystem II Protein Complex; D010940:Plant Proteins; D017382:Reactive Oxygen Species; D000099188:Alternative Oxidase; C030298:malic acid
keywords: Alternative oxidase; Arabidopsis thaliana; High light; Malate-oxaloacetate shuttle; Photorespiration; Photosynthesis; Pyridine nucleotides