DEEPER ROOTING 1 (DRO1) contributes to the downward gravitropic growth trajectory of roots upstream of lateral auxin transport in monocots and dicots. Loss of DRO1 function leads to horizontally oriented lateral roots and altered gravitropic set point angle, while loss of all three DRO family members results in upward, vertical root growth. Here, we attempt to dissect the roles of AtDRO1 by analyzing expression, protein localization, auxin gradient formation, and auxin responsiveness in the atdro1 mutant. Current evidence suggests AtDRO1 is predominantly a membrane-localized protein. Here we show that VENUS-tagged AtDRO1 driven by the native AtDRO1 promoter complemented an atdro1 Arabidopsis mutant and the protein was localized in root tips and detectable in nuclei. atdro1 primary and lateral roots showed impairment in establishing an auxin gradient upon gravistimulation as visualized with DII-VENUS, a sensor for auxin signaling and proxy for relative auxin distribution. Additionally, PIN3 domain localization was not significantly altered upon gravistimulation in atdro1 primary and lateral roots. RNA-sequencing revealed differential expression of known root development-related genes in atdro1 mutants. atdro1 lateral roots were able to respond to exogenous auxin and AtDRO1 gene expression levels in root tips were unaffected by the addition of auxin. Collectively, the data suggest that nuclear localization may be important for AtDRO1 function and suggests a more nuanced role for DRO1 in regulating auxin-mediated changes in lateral branch angle. KEY MESSAGE: DEEPER ROOTING 1 (DRO1) when expressed from its native promoter is predominately localized in Arabidopsis root tips, detectable in nuclei, and impacts auxin gradient formation.

中文翻译：

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AtDRO1在自然条件下在根尖中被核定位，并影响生长素的定位。

深度生根1（DRO1）有助于单子叶植物和双子叶植物横向生长素运输上游的根向下重力生长轨迹。DRO1功能的丧失会导致侧向根水平定向并改变重力定点角，而所有三个DRO家族成员的丧失都会导致垂直向上的根生长。在这里，我们尝试通过分析atdro1突变体中的表达，蛋白质定位，生长素梯度形成和生长素响应性来剖析AtDRO1的作用。当前证据表明AtDRO1主要是膜定位蛋白。在这里，我们显示由天然AtDRO1启动子驱动的VENUS标记的AtDRO1与atdro1拟南芥突变体互补，并且该蛋白位于根尖且可在细胞核中检测到。atdro1的初生根和侧生根显示出失重后建立生长素梯度的障碍，如DII-VENUS所见，DII-VENUS是一种生长素信号传递和相对生长素分布的代理。此外，在atdro1主根和侧根的去刺激后，PIN3域的定位没有明显改变。RNA测序揭示了atdro1突变体中与根发育相关的已知基因的差异表达。atdro1侧根能够响应外源生长素，并且添加生长素不会影响根尖中的AtDRO1基因表达水平。总体而言，数据表明核定位可能对AtDRO1功能很重要，并暗示DRO1在调节生长素介导的侧枝角变化中的作用更细微。关键信息：