Gravitropism of Arabidopsis thaliana Roots Requires the Polarization of PIN2 toward the Root Tip in Meristematic Cortical Cells[C][W]
Gravitropism of Arabidopsis thaliana Roots Requires the Polarization of PIN2 toward the Root Tip in Meristematic Cortical Cells[C][W]
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DOI：
10.1105/tpc.110.075317
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发表时间：
2010-06
期刊：
影响因子：
11.6
通讯作者：
Abidur Rahman;Maho Takahashi;Kyohei Shibasaki;Shuang Wu;T. Inaba;S. Tsurumi;T. Baskin
中科院分区：
文献类型：
--
作者：
Abidur Rahman;Maho Takahashi;Kyohei Shibasaki;Shuang Wu;T. Inaba;S. Tsurumi;T. Baskin
根的向重力性取决于生长素通过生长素外流载体PIN2从根冠流向伸长区。PIN2在表皮和侧根帽中的位置合适，而在皮层中的PIN2具有相反的极性。我们报告说，尽管如此，PIN2显然通过限制生长素的流动，在根皮质发挥最佳向重力性的作用。在根中，生长素从根尖到伸长区的运输，在这里被称为向南，控制着重力弯曲。向南的生长素极性运输，因此向重力性，取决于PIN形成的生长素外流载体PIN2的极性部署。在拟南芥中，PIN2在表皮和侧根帽中具有预期的向上定位；然而，该载体在分生组织的皮质细胞中定位于根尖(向根)，其功能是神秘的。我们使用药理学和遗传学工具在分生组织皮质细胞中导致PIN2的向下重新定位，而不会检测到改变其他类型细胞中的PIN2极化或PIN1极化。皮层PIN2的这种重新定位受到膜转运因子GNOM和调节性2-A蛋白磷酸酶A1亚单位(PP2AA1)的负调控，但不需要PINOID蛋白激酶。当GNOM被抑制时，PINOID丰度增加，PP2AA1部分固定，表明这两种蛋白都受到GNOM依赖的调节。特别是在大脑皮层，朝Shootward方向的PIN2伴随着向Shooward方向的极生长素运输的增强和向重力的减弱。这些结果表明，根皮质中的生长素流动对于最佳的向重反应是重要的。
Gravitropism of roots depends on a flow of auxin from the root cap to the zone of elongation via the auxin efflux carrier PIN2. While PIN2 in epidermis and lateral root cap is positioned appropriately, PIN2 in the cortex has the opposite polarity. We report that, despite this, PIN2 functions in the root cortex for optimal gravitropism, apparently by limiting the auxin flow. In the root, the transport of auxin from the tip to the elongation zone, referred to here as shootward, governs gravitropic bending. Shootward polar auxin transport, and hence gravitropism, depends on the polar deployment of the PIN-FORMED auxin efflux carrier PIN2. In Arabidopsis thaliana, PIN2 has the expected shootward localization in epidermis and lateral root cap; however, this carrier is localized toward the root tip (rootward) in cortical cells of the meristem, a deployment whose function is enigmatic. We use pharmacological and genetic tools to cause a shootward relocation of PIN2 in meristematic cortical cells without detectably altering PIN2 polarization in other cell types or PIN1 polarization. This relocation of cortical PIN2 was negatively regulated by the membrane trafficking factor GNOM and by the regulatory A1 subunit of type 2-A protein phosphatase (PP2AA1) but did not require the PINOID protein kinase. When GNOM was inhibited, PINOID abundance increased and PP2AA1 was partially immobilized, indicating both proteins are subject to GNOM-dependent regulation. Shootward PIN2 specifically in the cortex was accompanied by enhanced shootward polar auxin transport and by diminished gravitropism. These results demonstrate that auxin flow in the root cortex is important for optimal gravitropic response.