OsMSR3, a Small Heat Shock Protein, Confers Enhanced Tolerance to Copper Stress in Arabidopsis thaliana

Abstract

Copper is a mineral element essential for the normal growth and development of plants; however, excessive levels can severely affect plant growth and development. <i>Oryza sativa</i> L. multiple stress-responsive gene 3 <i>(OsMSR3)</i> is a small, low-molecular-weight heat shock protein (HSP) gene. A previous study has shown that <i>OsMSR3</i> expression improves the tolerance of <i>Arabidopsis</i> to cadmium stress. However, the role of <i>OsMSR3</i> in the Cu stress response of plants remains unclear, and, thus, this study aimed to elucidate this phenomenon in <i>Arabidopsis thaliana</i>, to further understand the role of small HSPs (sHSPs) in heavy metal resistance in plants. Under Cu stress, transgenic <i>A. thaliana</i> expressing <i>OsMSR3</i> showed higher tolerance to Cu, longer roots, higher survival rates, biomass, and relative water content, and accumulated more Cu, abscisic acid (ABA), hydrogen peroxide, chlorophyll, carotenoid, superoxide dismutase, and peroxidase than wild-type plants did. Moreover, <i>OsMSR3</i> expression in <i>A. thaliana</i> increased the expression of antioxidant-related and ABA-responsive genes. Collectively, our findings suggest that <i>OsMSR3</i> played an important role in regulating Cu tolerance in plants and improved their tolerance to Cu stress through enhanced activation of antioxidative defense mechanisms and positive regulation of ABA-responsive gene expression.