The gene expression profiles of mitochondrial respiratory components in Arabidopsis plants with differing amounts of <i>ALTERNATIVE OXIDASE1a</i> under high intensity light

We compared the expression of mitochondrial alternative oxidase (AOX) and other non-phosphorylating respiratory components (NPhPs) in wild type and <i>AOX1a</i> transgenic <i>Arabidopsis thaliana</i> following short-term transfer of plants to higher irradiance conditions to gain more insight into the mechanisms of AOX functioning under light. The <i>AOX1a</i> overexpressing line (XX-2) showed the highest amount of <i>AOX1a</i> transcripts and AOX1A synthesis during the entire experiment, and many NPhPs genes were down-regulated after 6–8 h under the higher light conditions. Antisense AS-12 plants displayed a compensatory effect, typically after 8 h of exposure to higher irradiance, by up-regulating their expression of the majority of genes encoding AOX and other respiratory components. In addition, AS-12 plants displayed ‘overcompensation effects’ prior to their transfer to high light conditions, i.e., they showed a higher expression level of certain genes. As a result, the ROS content in AS-12, as in XX-2, was consistently lower than in the wild type. All NPhPs genes share, in common with <i>AOX1a</i>, light- and stress-related <i>cis</i>-acting regulatory elements (CAREs) in their promoters. However, the expression of respiratory genes does not always depend on the level of <i>AOX1a</i> expression. This suggests the presence of multiple combinations of signaling pathways in gene induction. Based on our results, we outline possible directions for future research.