Influence of Mitochondrial Electron Transport Chain Inhibitors on Respiration and Gene Expression of Respiratory Components in a Greening Wheat Leaf

The effect of inhibitors of alternative oxidase and mitochondrial ETC complexes I and III on respiration and gene expression of components of cytochtome and nonphosphorylating pathways, and adenine nucleotide translocase was studied in the leaves of spring wheat ( Triticum aestivum L., cultivar Irgina) during greening. The effects of inhibitors were most pronounced at the early stage of greening (1–6 h). During this period, a decrease in the F v / F m value and a decrease in respiratory activity in comparison with the control variant were found. This fact indicated the sensitivity of developing chloroplasts to disruption of mitochondrial functions. Inhibitors had a multidirectional effect on the ratio of respiratory pathways and the expression of “respiratory” genes. The use of salicylhydroxamic acid, an alternative oxidase inhibitor, activated the cytochrome pathway, whose contribution increased to 75% of total respiration, and increased the relative expression of the genes encoding the subunits of complexes I, III, IV, and ATP synthase of mitochondrial ETC, especially in the first 6 h of greening. On the contrary, antimycin and rotenone, inhibitors of complex I and III, respectively, reduced the maximum activity and the relative content of transcripts of the genes for the main pathway subunits. At the same time, inhibition of the cytochrome pathway activated the alternative respiratory pathway (which accounted for 75% of the total O 2 uptake) and caused an increase in the content of transcripts of the alternative oxidase genes and components of other nonphosphorylating pathways. An increase in the relative level of ANT1 mRNA under the action of all inhibitors seems to be aimed at enhancing the transfer of ADP/ATP under conditions of energy deficiency with limited activity of the cytochrome pathway. The results indicate the coordinated nature of the functioning of the ETC components during the formation of the photosynthetic function of the leaf and confirm the idea on the important role of the redox state of the ETC in the regulation of the expression of “respiratory” genes and the functional state of chloroplasts.