Abstract
In the plant respiratory chain, there are two major uncoupling pathways, the alternative oxidase (AOX) and uncoupling protein (UCP). These are supposed to prevent production of ROS and maintain the TCA cycle activity.
Arabidopsis thaliana has AOX1a, 1b, 1c, 1d, 2 and UCP1-6. We used rosettes in plants transferred from 25oCto 10oC. The expressions of AOX1a and UCP5 increased after 3h. The cyanide-resistant respiratory rate and AOX protein amounts increased after the transfer. The amount of malondialdehyde, an index of oxidative damage, decreased with the AOX protein increase. AOX and UCP would function together for depletion of reducing equivalents at 10oC. These expression patterns are different from those at 4oC reported by Borecky et al. (2006). Thus, we questioned whether regulatory systems differently control AOX and UCP depending on the intensity of cold stress. We compared expression patterns of the respiratory chain components between 10oC and 4oC.
