• Root hairs (RHs) function in nutrient and water acquisition, root metabolite exudation, soil anchorage and plant–microbe interactions. Longer or more abundant RHs are potential breeding traits for developing crops that are more resource-use efficient and can improve soil health.
• While many genes are known to promote RH elongation, relatively little is known about genes and mechanisms that constrain RH growth.
• Here we demonstrate that a DOMAIN OF UNKNOWN FUNCTION 506 (DUF506) protein, AT3G25240, negatively regulates Arabidopsis thaliana RH growth. The AT3G25240 gene is strongly and specifically induced during phosphorus (P)-limitation. Mutants of this gene, which we call REPRESSOR OF EXCESSIVE ROOT HAIR ELONGATION 1 (RXR1), have much longer RHs, higher phosphate content and seedling biomass, while overexpression of the gene exhibits opposite phenotypes. Co-immunoprecipitation, pull-down and bimolecular fluorescence complementation (BiFC) analyses reveal that RXR1 physically interacts with a RabD2c GTPase in nucleus, and a rabd2c mutant phenocopies the rxr1 mutant. Furthermore, N-terminal variable region of RXR1 is crucial for inhibiting RH growth. Overexpression of a Brachypodium distachyon RXR1 homolog results in repression of RH elongation in Brachypodium.
• Taken together, our results reveal a novel DUF506-GTPase module with a prominent role in repression of plant RH elongation especially under P stress.

中文翻译：

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一种磷限制诱导的、功能保守的 DUF506 蛋白是植物根毛伸长的抑制因子

• 根毛 (RH) 在养分和水分获取、根代谢物渗出、土壤锚固和植物-微生物相互作用中发挥作用。更长或更丰富的 RH 是开发资源利用效率更高并可以改善土壤健康的作物的潜在育种特征。
• 虽然已知许多基因可以促进 RH 延长，但对限制 RH 生长的基因和机制知之甚少。
• 在这里，我们证明了未知功能域 506 (DUF506) 蛋白 AT3G25240 负调节拟南芥RH 生长。AT3G25240基因在磷 (P) 限制期间被强烈且特异性地诱导。该基因的突变体，我们称之为根毛过度伸长抑制因子 1 (RXR1)，具有更长的 RH、更高的磷酸盐含量和幼苗生物量，而该基因的过表达表现出相反的表型。免疫共沉淀、下拉和双分子荧光互补 (BiFC) 分析表明，RXR1 与细胞核中的 RabD2c GTPase 物理相互作用，并且rabd2c突变体对rxr1进行表型复制突变体。此外，RXR1 的 N 末端可变区对于抑制 RH 生长至关重要。Brachypodium distachyon RXR1同源物的过表达导致Brachypodium中 RH 伸长的抑制。
• 总之，我们的结果揭示了一种新的 DUF506-GTPase 模块，它在抑制植物 RH 伸长特别是在 P 胁迫下具有突出的作用。