Biochemical characterization of Arabidopsis ntrc mutants during dark-induced senescence

Abstract Thioredoxins are invoved in redox regulation of many cellular processes. In this study the role of NADP+Thioredoxin reductase C (NTRC) in the control of leaf senescence was investigated by biochemical characterization of Arabidopsis ntrc mutants. Forty days old wild type and two ntrc mutant lines were incubated either under normal dark-light or continous darkness regimes for 6 days as control and senescence treatment, respectively. Growth parameters, the contents of carbohydrates, pigments and the activity of some antioxidant enzymes were compared between wild type and ntrc mutant lines during dark induced senescence. Darkness led to decreased fresh and dry weights, chlorophylls and carotenoides, starch and protein contents in both wild type and mutant plants and there were no significant differences in the interactions of genotypes and treatments regarding to theses parameters. Darkness also induced the accumulation of anthocyanins, total and non-reducing sugars however, the accumulation of the carbohydrates in mutant lines was more pronounciated than wild type plants and again there were no significant differences in response of wild type and mutants to dark treatment. The activities of catalase, peroxidase and polyphenol oxidase of mutant lines were significantly greater than wild type plants. While darkness decreased the activities of ascorbate peroxidase and catalase it led to increased activities of peroxidase and polyphenol oxidase especially in the mutant lines. There were significant differences in the activities of all four enzymes between mutant and wild type plants in response to darkness. Thus, it appears that defects in NTRC mainly affects the activities of antioxidant enzymes rather than the other studied biochemical parameters of plants during the senescence process. This study might be useful in future breeding programs for controlling senecence process to achieve better performance of crop plants.