The lack of alternative oxidase at low temperature leads to a disruption of the balance in carbon and nitrogen metabolism, and to an up-regulation of antioxidant defence systems in Arabidopsis thaliana leaves.
Alternative oxidase (AOX) catalyses the ATP-uncoupling cyanide (CN)-resistant pathway. In this study, our aim was to clarify the physiological role of AOX at low temperature. We examined the effect of low-temperature treatment on CN-resistant respiration (CN-resistant R) and on the transcription of respiratory components in wild-type (WT) and aox1a knock-out transgenic (aox1a) Arabidopsis thaliana plants. In WT leaves, the expression of AOX1a mRNA was strongly induced by the low-temperature treatment, and thus CN-resistant R increased during low-temperature treatment. In aox1a, the CN-sensitive respiration, and the expression of NDB2 and UCP1 were increased compared with WT. We compared several physiological parameters between WT and aox1a. Low-temperature treatment did not result in a visible phenotype to distinguish aox1a from WT. In aox1a, several antioxidant defence genes were induced, and the malondialdehyde content was lower than in WT. Starch content and a ratio of carbon to nitrogen were higher in aox1a than in WT. Our results indicate that a lack of AOX was linked to a difference in the carbon and nitrogen balance, and an up-regulation of the transcription of antioxidant defence system at low temperature. It is likely that AOX is a necessary component in antioxidant defence mechanisms and for the control of a balanced metabolism.
Department of Biological Sciences, Graduate School of Science, Osaka University, 1-1 Machikaneyama-cho, Toyonaka, Osaka, 560-0043, Japan. chihiro-nabe@biol.s.u-tokyo.ac.jp
Chihiro K
CK
Watanabe
Takushi
T
Hachiya
Ichiro
I
Terashima
Ko
K
Noguchi
D000596:Amino Acids / Q000378:metabolism; D000975:Antioxidants; D017360:Arabidopsis / Q000166:cytology / Q000201:enzymology* / Q000276:immunology; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D002241:Carbohydrates; D002244:Carbon / Q000378:metabolism*; D019069:Cell Respiration; D002734:Chlorophyll / Q000378:metabolism; D003080:Cold Temperature; D004269:DNA, Bacterial; D005453:Fluorescence; D018506:Gene Expression Regulation, Plant; D008315:Malondialdehyde / Q000378:metabolism; D024101:Mitochondrial Proteins; D016254:Mutagenesis, Insertional; D009584:Nitrogen / Q000378:metabolism*; D010088:Oxidoreductases / Q000172:deficiency* / Q000378:metabolism; D018515:Plant Leaves / Q000166:cytology / Q000235:genetics / Q000276:immunology*; D010940:Plant Proteins; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic; D015854:Up-Regulation; D000099188:Alternative Oxidase
D000596:Amino Acids; D000975:Antioxidants; D029681:Arabidopsis Proteins; D002241:Carbohydrates; D002244:Carbon; D002734:Chlorophyll; D004269:DNA, Bacterial; D008315:Malondialdehyde; D024101:Mitochondrial Proteins; D009584:Nitrogen; D010088:Oxidoreductases; D010940:Plant Proteins; D012333:RNA, Messenger; D000099188:Alternative Oxidase; C036483:T-DNA