Cadmium (Cd) is a biologically non-essential and toxic heavy metal leaking to the environment via natural emission or anthropogenic activities, thereby contaminating crops and threatening human health. Metallothioneins (MTs) are a group of metal-binding proteins playing critical roles in metal allocation and homeostasis. In this study, we identified a novel function of OsMT1e from rice plants. OsMT1e was dominantly expressed in roots at all developmental stages and, to less extent, expressed in leaves at vegetative and seed filling stages. OsMT1e was mainly targeted to the nucleus and substantially induced by Cd exposure. Expression of OsMT1e in a yeast Cd-sensitive strain ycf1 conferred cellular tolerance to Cd, even though the ycf1+OsMT1e cells accumulated more Cd than the control cells (ycf1+pYES2). Both transgenic rice overexpressing (OX) and repressing OsMT1e by RNA interference (RNAi) were developed. Phenotypic analysis revealed that OsMT1e overexpression enhanced the rice growth concerning the increased shoot or root elongation, dry weight and chlorophyll contents, whereas the RNAi lines displayed a sensitive growth phenotype compared to wild-type. Assessment with 0.5, 2 and 10 μM Cd for two weeks revealed that the RNAi lines accumulated less Cd, while the OX lines had an increased Cd accumulation in root and shoot tissues. The contrasting Cd accumulation phenotypes between the OX and RNAi lines were further confirmed by a long-term study with 0.5 μM Cd for one month. Overall, the study unveiled a new function of OsMT1e in rice, which can be potentially used for engineering genotypes for phytoremediation or minimizing Cd in rice crops.

镉（Cd）是一种生物上不必要的有毒重金属，它通过自然排放或人为活动泄漏到环境中，从而污染农作物并威胁人类健康。金属硫蛋白（MTs）是一组金属结合蛋白，在金属分配和体内平衡中起关键作用。在这项研究中，我们确定了水稻植株中OsMT1e的新功能。OsMT1e在所有发育阶段均以根为主，而在营养和种子充实阶段则以叶为主。OsMT1e主要针对细胞核，并且基本上由Cd暴露诱导。的表达OsMT1e在酵母镉敏感性菌株ycf1即使ycf1 + OsMT1e细胞比对照细胞（ycf1 + pYES2）积累了更多的Cd，仍可赋予细胞对Cd的耐受性。开发了通过RNA干扰（RNAi）的转基因水稻过表达（OX）和抑制OsMT1e。表型分析表明，OsMT1e过表达促进了水稻的生长，涉及芽或根伸长，干重和叶绿素含量的增加，而与野生型相比，RNAi系表现出敏感的生长表型。用0.5、2和10μMCd评估两周后发现，RNAi品系积累的Cd较少，而OX品系在根和芽组织中的Cd积累增加。OX和RNAi系之间的Cd积累表型形成鲜明对比，该研究通过0.5μMCd进行的一项长期研究进一步证实。总体而言，该研究揭示了OsMT1e在水稻中的新功能，该功能可潜在地用于工程基因型的植物修复或将水稻中的Cd降至最低。