Washington State University Tree Fruit Research and Extension Center, Wenatchee, WA, 98801, USA.
USDA-ARS Appalachian Fruit Research Station, Kearneysville, WV, 25430, USA.
Plant Mol Biol. 2020 May;103(1-2):197-210. doi: 10.1007/s11103-020-00984-2. Epub 2020 Mar 4.
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.
DEEPER ROOTING 1（DRO1）有助于单子叶植物和双子叶植物中生长素横向运输上游的根向下的向地生长轨迹。DRO1 功能丧失导致水平定向的侧根和改变的向地性设定点角度，而三个 DRO 家族成员的丧失导致向上、垂直的根生长。在这里，我们试图通过分析 atdro1 突变体中的表达、蛋白定位、生长素梯度形成和生长素反应来剖析 AtDRO1 的作用。目前的证据表明，AtDRO1 主要是一种膜定位蛋白。在这里，我们展示了由 native AtDRO1 启动子驱动的 VENUS 标记的 AtDRO1 互补了 atdro1 拟南芥突变体，并且该蛋白定位于根尖并可在核中检测到。在重力刺激下，atro1 主根和侧根在建立生长素梯度方面表现出障碍，这可以通过 DII-VENUS 可视化，DII-VENUS 是生长素信号的传感器，也是相对生长素分布的代表。此外，在重力刺激下，atro1 主根和侧根中 PIN3 结构域的定位没有明显改变。RNA-seq 显示在 atdro1 突变体中，已知的根发育相关基因的表达存在差异。atro1 侧根能够对外源生长素做出反应，并且添加生长素对根尖中 AtDRO1 基因表达水平没有影响。总的来说，这些数据表明核定位可能对 AtDRO1 功能很重要，并表明 DRO1 在调节生长素介导的侧枝角度变化方面具有更细致的作用。关键信息：当从其天然启动子表达时，DEEPER ROOTING 1（DRO1）主要定位于拟南芥根尖，可在核中检测到，并影响生长素梯度形成。
