Widespread contamination of agricultural soil with toxic metals such as cadmium (Cd) is a major threat to crop production and human health. Metallochaperones are a unique class of proteins that play pivotal roles in detoxifying metallic ions inside cells. In this study, we investigated the biological function of an uncharacterized metallochaperone termed OsHIPP29 in rice plants and showed that OsHIPP29 resides in the plasma membrane and nucleus and detoxifies excess Cd and Zn. OsHIPP29 was primarily expressed in shoots during the vegetative stage and in leaf sheath and spikelet at the flowering stage. It can be differentially induced by excess Cd, Zn, Cu, Fe and Mn. To identify the function of OsHIPP29 in mediating rice response to Cd stress, we examined a pair of OsHIPP29 mutants, RNAi lines and transgenic rice overexpressing OsHIPP29 (OX) under Cd stress. Both mutant and RNAi lines are sensitive to Cd in growth as reflected in decreased plant height and dry biomass. In contrast, the OX lines showed better growth under Cd exposure. Consistent with the phenotype, the OX lines accumulated less Cd in both root and shoot tissues, whereas OsHIPP29 knockout led to higher accumulation of Cd. These results point out that expression of OsHIPP29 is able to contribute to Cd detoxification by reducing Cd accumulation in rice plants. Our work highlights the significance of OsHIPP29-mediated reduced Cd in rice plants, with important implications for further developing genotypes that will minimize Cd accumulation in rice and environmental risks to human health.

中文翻译：

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开发具有OsHIPP29基因座的抗镉水稻基因型，以限制镉在稻田中的积累。

农业土壤广泛受到镉（Cd）等有毒金属的污染，对作物生产和人类健康构成重大威胁。金属伴侣蛋白是一类独特的蛋白质，在排毒细胞内的金属离子中起关键作用。在这项研究中，我们调查了水稻植物中未表征的金属伴侣蛋白OsHIPP29的生物学功能，并显示OsHIPP29驻留在质膜和细胞核中，并对过量的Cd和Zn进行解毒。OsHIPP29主要在营养期的枝条中表达，在开花期的叶鞘和小穗中表达。过量的Cd，Zn，Cu，Fe和Mn可以诱导它分化。为了确定OsHIPP29在介导水稻对Cd胁迫的响应中的功能，我们检查了一对OsHIPP29突变体，Cd胁迫下过表达OsHIPP29（OX）的RNAi系和转基因水稻。突变株和RNAi株系均对Cd的生长敏感，这反映在植物高度和干燥生物量的降低上。相反，OX线在Cd暴露下显示出更好的生长。与表型一致，OX系在根和芽组织中积累的Cd较少，而OsHIPP29基因敲除导致Cd的积累较高。这些结果指出，OsHIPP29的表达能够通过减少水稻植株中Cd的积累来促进Cd的解毒。我们的工作凸显了OsHIPP29介导的水稻植株中Cd还原的重要性，这对进一步开发基因型具有重要意义，该基因型将使Cd在水稻中的积累降至最低，并危害人类健康。突变株和RNAi株系均对Cd的生长敏感，这反映在植物高度和干燥生物量的降低上。相反，OX线在Cd暴露下显示出更好的生长。与表型一致，OX系在根和芽组织中积累的Cd较少，而OsHIPP29基因敲除导致Cd的积累较高。这些结果指出，OsHIPP29的表达能够通过减少水稻植株中Cd的积累来促进Cd的解毒。我们的工作凸显了OsHIPP29介导的水稻植株中Cd还原的重要性，这对进一步开发基因型具有重要意义，该基因型将使Cd在水稻中的积累降至最低，并危害人类健康。突变株和RNAi株系均对Cd的生长敏感，这反映在植物高度和干燥生物量的降低上。相反，OX线在Cd暴露下显示出更好的生长。与表型一致，OX系在根和芽组织中积累的Cd较少，而OsHIPP29基因敲除导致Cd的积累较高。这些结果指出，OsHIPP29的表达能够通过减少水稻植株中Cd的积累来促进Cd的解毒。我们的工作凸显了OsHIPP29介导的水稻植株中Cd还原的重要性，这对进一步开发基因型具有重要意义，该基因型将使Cd在水稻中的积累降至最低，并危害人类健康。OX系在根和芽组织中积累的Cd较少，而OsHIPP29敲除导致Cd的积累较高。这些结果指出，OsHIPP29的表达能够通过减少水稻植株中Cd的积累来促进Cd的解毒。我们的工作凸显了OsHIPP29介导的水稻植株中Cd还原的重要性，这对进一步开发基因型具有重要意义，该基因型将使Cd在水稻中的积累降至最低，并危害人类健康。OX系在根和芽组织中积累的Cd较少，而OsHIPP29敲除导致Cd的积累较高。这些结果表明，OsHIPP29的表达能够通过减少水稻植株中Cd的积累来促进Cd的解毒。我们的工作凸显了OsHIPP29介导的水稻植株中Cd还原的重要性，这对进一步开发基因型具有重要意义，该基因型将使Cd在水稻中的积累降至最低，并危害人类健康。