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

Shu-Hsuan Hu,Tsung-Luo Jinn

doi:10.3390/plants11050619

Abstract

It has been reported that the mitochondrial carrier family proteins of AtMTM1 and AtMTM2 are necessary for manganese superoxide dismutase (MnSOD) activation in Arabidopsis, 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 AtMnSOD-overexpressing and AtMnSOD-knockdown mutant plants treated with the widely used oxidative stressors including MV, NaCl, H2O2, and tert-butyl hydroperoxide (t-BH), we revealed that Arabidopsis MnSOD was crucial for root-growth control and superoxide scavenging ability. In addition, it has been reported that E. coli MnSOD activity is inhibited by Fe and that MTM1-mutated yeast cells exhibit elevated Fe content and decreased MnSOD activity, which can be restored by the Fe2+-specific chelator, bathophenanthroline disulfonate (BPS). However, we showed that BPS inhibited MnSOD activity in AtMTM1 and AtMTM2 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 AtMTM1 and AtMTM2 mutants under MV stress, indicating the importance of AtMTM1 in roots and AtMTM2 in shoots for maintaining Fe/Mn balance.

Highlights

It has been reported that the mitochondrial carrier family proteins of AtMTM1 and AtMTM2 are necessary for manganese superoxide dismutase (MnSOD) activation in Arabidopsis, and are responsive to methyl viologen (MV)-induced oxidative stress
We showed that MnSOD activity was similar between Col and MnSOD-OE plants, plates containing these stressors [31], and we have reported that AtMTM1, AtMTM2, and and was gene lowerexpression in msd1 plants
MnSOD activation is affected by Fe homeostasis, and we suggested that the disrupted systems by Fe homeostasis include MnSOD apoprotein synthesis in the cytosol, Mn binding to MnSOD via mitochondrial AtMTM1 and AtMTM2, or tetrameric MnSOD activation in the mitochondrial matrix

Summary

Introduction

It has been reported that the mitochondrial carrier family proteins of AtMTM1 and AtMTM2 are necessary for manganese superoxide dismutase (MnSOD) activation in Arabidopsis, and are responsive to methyl viologen (MV)-induced oxidative stress. Superoxide dismutases (SODs) are distributed in the cytoplasm, chloroplasts, and mitochondria of prokaryotic and eukaryotic cells [1,2,3] They are classified as CuZnSOD, FeSOD, MnSOD, or NiSOD according to the transition metal cofactor ions at the active site [4,5,6]. It has been reported that AtMnSOD-overexpressing plants exhibit increased catalase and peroxidase activities, with decreased malondialdehyde content after NaCl treatment, and maintain a higher germination rate in the presence of oxidative stressors, such as methyl viologen (MV)

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