Responses of genes of DNA repair alternative oxidase and pro-/antioxidant state in Arabidopsis thaliana with altered expression of AOX1a to gamma irradiation.
The gene expression profiles of mitochondrial respiratory components in Arabidopsis plants with differing amounts of ALTERNATIVE OXIDASE1a under high intensity light.
The results highlight the importance of alternative oxidase (AOX) in plant response to UVB for the control of a balanced metabolism and indicate that AOX1a plays a key role in the regulation of the stress response.
Similar to the expression of AOX1a the expression of AOX1d was also significantly elevated due to Pseudomonas syringae harpin protein treatment. Similar to the expression and activity of AOX the transcript level of UCP4 UCP5 and the UCP activity increased due to Pseudomonas syringae harpin protein treatment and the consequential oxidative burst.
MYB DOMAIN PROTEIN29 (MYB29) mutants have increased levels of ALTERNATIVE OXIDASE1a (AOX1a) transcript and protein compared to wild type after induction with antimycin A.
AOX1A plays a significant role in sustaining the chloroplastic redox state and energization to optimize photosynthesis by regulating cellular redox homeostasis and ROS generation when electron transport through the COX pathway is disturbed at complex III.
The authors propose a working model where AOX1a acts early in the response to Cd and activates or maintains a mitochondrial signalling pathway impacting on cellular antioxidative defence at the post-transcriptional level.
PP2A-B'gamma physically interacts with the cytoplasmic form of aconitase and PP2A-B'gamma impacts reactive oxygen species homeostasis by controlling the abundance of specific alternative oxidase isoforms AOX1A and AOX1D in leaf mitochondria.
Overexpression of AOX1a reduced mitochondrial ROS production by maintaining the mitochondrial electron flux and alleviated subsequent mitochondrial dysfunction and caspase-3-like activation in Al-induced programmed cell death.
Foliar NO3 (-) assimilation was enhanced in both aox1a and ucp1 compared with the wild-type suggesting that foliar NO3 (-) assimilation is probably driven by a decreased capacity of mAET and an increase in reductant within the cytosol.
RAO2/Arabidopsis NAC domain-containing protein17 (ANAC017) as a direct positive regulator of AOX1a. Plants with mutated rao2/anac017 were more stress sensitive.
The ability of AOX1a and AOX2 to substitute for PTOX in the correct physiological and developmental contexts is a striking example of the capacity of a mitochondrial protein to replace the function of a chloroplast protein.
These results suggest that AOX plays an important role in rapid acclimation of the respiratory chain to sHL which may support efficient photosynthetic performance.
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