Glutaredoxins (GRXs) are small oxidoreductase enzymes that can reduce disulfide bonds in target proteins. The class III GRX gene family is unique to land plants, and Arabidopsis thaliana has 21 class III GRXs, which remain largely uncharacterized. About 80% of A. thaliana class III GRXs are transcriptionally regulated by nitrate, and several recent studies have suggested roles for these GRXs in nitrogen signaling. Our objective was to functionally characterize two nitrate‐induced GRX genes, AtGRXS5 and AtGRXS8, defining their roles in signaling and development in the A. thaliana root. We demonstrated that AtGRXS5 and AtGRXS8 are primarily expressed in root and shoot vasculature (phloem), and that the corresponding GRX proteins display nucleo‐cytosolic subcellular localization. Ectopic expression of AtGRXS8 in transgenic plants caused major alterations in root system architecture: Normal primary root development, but a near absence of lateral roots. RNA sequencing demonstrated that the roots of AtGRXS8‐overexpressing plants show strongly reduced transcript abundance for many primary nitrate response genes, including the major high‐affinity nitrate transporters. Correspondingly, high‐affinity nitrate uptake and the transport of nitrate from roots to shoots are compromised in AtGRXS8‐overexpressing plants. Finally, we demonstrated that the AtGRXS8 protein can physically interact with the TGA1 and TGA4 transcription factors, which are central regulators of early transcriptional responses to nitrate in A. thaliana roots. Overall, these results suggest that AtGRXS8 acts to quench both transcriptional and developmental aspects of primary nitrate response, potentially by interfering with the activity of the TGA1 and TGA4 transcription factors.

中文翻译：

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谷氧还蛋白 AtGRXS8 抑制拟南芥根部对硝酸盐的转录和发育反应。


谷氧还蛋白 (GRX) 是一种小型氧化还原酶，可以减少目标蛋白中的二硫键。 III 类 GRX 基因家族是陆地植物所独有的，拟南芥有 21 个 III 类 GRX，但这些基因在很大程度上仍未被表征。大约 80% 的拟南芥III 类 GRX 受硝酸盐转录调节，最近的几项研究表明这些 GRX 在氮信号传导中的作用。我们的目标是对两个硝酸盐诱导的 GRX 基因AtGRXS5和AtGRXS8进行功能表征，确定它们在拟南芥根部信号传导和发育中的作用。我们证明AtGRXS5和AtGRXS8主要在根和芽脉管系统（韧皮部）中表达，并且相应的 GRX 蛋白显示核胞质亚细胞定位。 AtGRXS8在转基因植物中的异位表达引起根系结构的重大改变：初生根发育正常，但侧根几乎缺失。 RNA 测序表明， AtGRXS8过度表达植物的根部显示许多初级硝酸盐反应基因（包括主要的高亲和力硝酸盐转运蛋白）的转录本丰度大大降低。相应地，在AtGRXS8过度表达的植物中，高亲和力的硝酸盐吸收和硝酸盐从根到芽的运输受到损害。最后，我们证明 AtGRXS8 蛋白可以与 TGA1 和 TGA4 转录因子发生物理相互作用，TGA1 和 TGA4 转录因子是拟南芥根部硝酸盐早期转录反应的中心调节因子。 总体而言，这些结果表明AtGRXS8可能通过干扰 TGA1 和 TGA4 转录因子的活性来抑制初级硝酸盐反应的转录和发育方面。