Functional Study of Yeast MTM-like Genes in MnSOD Activation of Arabidopsis
Date Issued
2012
Date
2012
Author(s)
Lin, Shu-Fan
Abstract
Manganese-containing superoxide dismutase (MnSOD) constitutes the first line of mitochondria defense against ROS, but the mechanism of the MnSOD activation still remains unclear. The MTM1 protein (manganese trafficking factor for mitochondrial SOD2) has been identified in yeast, which is a member of the mitochondrial carrier family (MCF), affecting the yeast mitochondrial MnSOD (SOD2) activity in an uncertain pathway. Two yeast MTM1-like genes, AtMTM1 (At4g27940) and AtMTM2 (At2g46320), were identified by sequence similarity, and both genes also encoded mitochondrial substrate carrier proteins in Arabidopsis (Arabidopsis thaliana). Here, we used genetic and transgenic approaches to study the molecular mechanism underlying the relationship between Arabidopsis MTMs (AtMTMs) and MnSOD (AtMSD1). We confirmed that expressing both AtMTM genes in a yeast MTM1-knockout strain can recover ySOD2 activity, implying AtMTMs functional similarity as with the yeast MTM1. We also found that the protein products of AtMTM1 and AtMTM2 were localized in mitochondria and an interactive relationship existed among AtMTM1, AtMTM2 and AtMSD1. The expression patterns of AtMTM1 and AtMTM2 were significantly different in various organs, and also differ to the response under oxidative stress. Besides, the root length was inhibited in the Atmtm1-RNAi lines but increased in Atmtm2-knockout mutants under oxidative stress. Notably, we observed the MnSOD activity was decreased and associated with an increase of FeSOD activity in the Atmtm1 and Atmtm2 double mutant lines. In summary, both AtMTM1 and AtMTM2 could affect the activity of MnSOD, but the functions between these two MCF proteins were not all the same. In Arabidopsis, they could not only interact to the one another, but participated in a complex mechanism of ion homeostasis. Moreover, the regulation of ionic balance mechanisms may stretch across mitochondria and chloroplast. These results demonstrated that the activation of MnSOD and ion homeostasis in plants were much complicated then in yeast.
Subjects
Arabidopsis
superoxide dismutase(SOD)
MnSOD
metal cofactor
oxidative stress
ion homeostasis
Type
thesis
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