SUMMARY. Multigene families are widely represented in the genomes of higher plants, and are required for the reliability of cellular functions. The damage of individual genes can be compensated by diverse meta-bolic alterations, but the exact mechanisms of such compensations still remain not fully understood. Here we present novel data regarding the mechanisms of metabolic compensation in photorespiratory knock-out mutants cat2, cat3 and cat2cat3 of Arabidopsis thaliana, which are lacking activity of catalase isoforms CAT2 and CAT3. It was found that cultivation of the mutants under low light at optimal or increased temperature did not result in any morphological, physiological or biochemical signs of oxidative stress. Each of the mutant lines shows specific features of the compensatory mechanisms. Increased activity of CAT3 isoenzyme was found in the cat2 mutant, whereas cat3 and cat2cat3 the demonstrate induction of CAT1, an isoform normally absent in young leaves, as well as the activation of peroxidases, namely APX and POD. The comparison of these results and earlier published data revealed that the lack of CAT2 and CAT3 isoforms is compensated by preferential activation of non-enzymatic and enzymatic protection mechanisms, respectively.
Keywords:
