Despite extensive studies on the effects of elevated atmospheric CO₂ concentrations ([CO₂]) on rice, the molecular mechanisms and signaling events underlying the adaptation of plants remain largely elusive. Here, we report that OsRab6a, which encodes a small GTPase, is involved in the regulation of rice growth, grain yield, and accumulation of iron (Fe) in response to elevated [CO₂] (e[CO₂]). We generated transgenic plants with OsRab6a-overexpression (-OE) together with OsRab6a-RNAi lines, and found no differences in growth and grain yield among them and wild-type (WT) plants under ambient [CO₂] conditions. Under e[CO₂] conditions, growth and grain yield of the WT and OsRab6a-OE plants were enhanced, with a greater effect being observed in the latter. In contrast, there were no effects of e[CO₂] on growth and grain yield of the OsRab6a-RNAi plants. Photosynthetic rates in both the WT and OsRab6a-OE plants were stimulated by e[CO₂], with the magnitude of the increase being higher in OsRab6a-OE plants. Fe concentrations in vegetative tissues and the grain of the WT and transgenic plants were reduced by e[CO₂], and the magnitude of the decrease was lower in the OE plants than in the WT and RNAi plants. Genes associated with Fe acquisition in the OsRab6a-OE lines exhibited higher levels of expression than those in the WT and the RNAi lines under e[CO₂]. Analysis of our data using Dunnett’s multiple comparison test suggested that OsRab6a is an important molecular regulator that underlies the adaptation of rice to e[CO₂] by controlling photosynthesis and Fe accumulation.

中文翻译：

---

水稻小GTPase Rab6a参与响应CO2富集的谷物产量和铁营养的调节。

尽管对升高的大气CO ₂浓度（[CO ₂ ]）对水稻的影响进行了广泛的研究，但植物适应的分子机制和信号传导事件仍然难以捉摸。在这里，我们报告说，编码小的GTPase的OsRab6a参与了水稻生长，谷物产量和响应[CO ₂ ]（e [CO ₂ ]）的铁（Fe）积累的调节。我们用OsRab6a-过表达（-OE）以及OsRab6a- RNAi系生成了转基因植物，在环境[CO ₂ ]条件下，它们与野生型（WT）植物在生长和籽粒产量上均没有差异。在e [CO _2下WT和OsRab6a -OE植物的条件，生长和谷物产量均得到提高，在后者中观察到更大的效果。相反，e [CO ₂ ]对OsRab6a -RNAi植物的生长和籽粒产量没有影响。在WT和两个光合速率OsRab6a -OE植物通过e [CO刺激₂ ]，其中增加是在更高的幅度OsRab6a -OE植物。e [CO ₂ ]降低了野生型和转基因植物的营养组织和籽粒中的铁浓度，OE植物的降低幅度小于野生型和RNAi植物。OsRab6a中与铁收购相关的基因-OE系比e [CO ₂ ]下的WT和RNAi系表现出更高的表达水平。使用Dunnett的多重比较测试对我们的数据进行分析表明，OsRab6a是一种重要的分子调节剂，通过控制光合作用和铁的积累，使水稻适应e [CO ₂ ]。