Impacts of Mn, Fe, and Oxidative Stressors on MnSOD Activation by AtMTM1 and AtMTM2 in .

It has been reported that the mitochondrial carrier family proteins of AtMTM1 and AtMTM2 are necessary for manganese superoxide dismutase (MnSOD) activation in , and are responsive to methyl viologen (MV)-induced oxidative stress. In this study, we showed that MnSOD activity was enhanced specifically by Mn treatments. By using -overexpressing and -knockdown mutant plants treated with the widely used oxidative stressors including MV, NaCl, HO, and tert-butyl hydroperoxide (t-BH), we revealed that MnSOD was crucial for root-growth control and superoxide scavenging ability. In addition, it has been reported that . MnSOD activity is inhibited by Fe and that -mutated yeast cells exhibit elevated Fe content and decreased MnSOD activity, which can be restored by the Fe-specific chelator, bathophenanthroline disulfonate (BPS). However, we showed that BPS inhibited MnSOD activity in and single- and double-mutant protoplasts, implying that altered Fe homeostasis affected MnSOD activation through AtMTM1 and AtMTM2. Notably, we used inductively coupled plasma-optical emission spectrometry (ICP-OES) analysis to reveal an abnormal Fe/Mn ratio in the roots and shoots of and mutants under MV stress, indicating the importance of AtMTM1 in roots and AtMTM2 in shoots for maintaining Fe/Mn balance.