• Transport and homeostasis of transition metals in chloroplasts, which are accurately regulated to ensure supply and to prevent toxicity induced by these metals, are thus crucial for chloroplast function and photosynthetic performance. However, the mechanisms that maintain the balance of transition metals in chloroplasts remain largely unknown.
• We have characterized an albino‐revertible green 1 (arg1) rice mutant. ARG1 encodes an evolutionarily conserved protein belonging to the ATP‐binding cassette (ABC) transporter family. Protoplast transfection and immunogold‐labelling assays showed that ARG1 is localized in the envelopes and thylakoid membranes of chloroplasts.
• Measurements of metal contents, metal transport, physiological and transcriptome changes revealed that ARG1 modulates cobalt (Co) and nickel (Ni) transport and homeostasis in chloroplasts to prevent excessive Co and Ni from competing with essential metal cofactors in chlorophyll and metal‐binding proteins acting in photosynthesis. Natural allelic variation in ARG1 between indica and temperate japonica subspecies of rice is coupled with their different capabilities for Co transport and Co content within chloroplasts. This variation underpins the different photosynthetic capabilities in these subspecies.
• Our findings link the function of the ARG1 transporter to photosynthesis, and potentially facilitate breeding of rice cultivars with improved Co homeostasis and consequently improved photosynthetic performance.

中文翻译：

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水稻叶绿体定位的ABC转运蛋白ARG1调节钴和镍的体内稳态并有助于光合能力。

• 因此，对叶绿体中过渡金属的运输和体内平衡进行了精确调节，以确保其供应并防止这些金属引起的毒性，因此对于叶绿体功能和光合性能至关重要。但是，维持叶绿体中过渡金属平衡的机理仍然未知。
• 我们已经表征了白化病可逆的绿色1（arg1）水稻突变体。ARG1编码属于ATP结合盒（ABC）转运蛋白家族的进化保守蛋白。原生质体转染和免疫金标记检测表明，ARG1位于叶绿体的包膜和类囊体膜中。
• 对金属含量，金属转运，生理和转录组变化的测量表明，ARG1调节叶绿体中的钴（Co）和镍（Ni）转运和体内稳态，以防止过量的Co和Ni与叶绿素和金属结合蛋白中的必需金属辅因子竞争在光合作用中。在天然等位基因变异ARG1之间籼稻和温带粳稻米的亚种被加上了叶绿体内联合运输和Co含量的不同的能力。这种变化巩固了这些亚种中不同的光合作用能力。
• 我们的发现将ARG1转运蛋白的功能与光合作用联系起来，并有可能通过改良的Co稳态和因此提高的光合作用促进水稻品种的选育。