Jones Angharad R, Kramer Eric M, Knox Kirsten, Swarup Ranjan, Bennett Malcolm J, Lazarus Colin M, Leyser H M Ottoline, Grierson Claire S
School of Biological Sciences, University of Bristol, BS8 1UG, UK.
Nat Cell Biol. 2009 Jan;11(1):78-84. doi: 10.1038/ncb1815. Epub 2008 Dec 14.
The plant hormone auxin controls root epidermal cell development in a concentration-dependent manner. Root hairs are produced on a subset of epidermal cells as they increase in distance from the root tip. Auxin is required for their initiation and continued growth, but little is known about its distribution in this region of the root. Contrary to the expectation that hair cells might require active auxin influx to ensure auxin supply, we did not detect the auxin-influx transporter AUX1 in root-hair cells. A high level of AUX1 expression was detected in adjacent non-hair cell files. Non-hair cells were necessary to achieve wild-type root-hair length, although an auxin response was not required in these cells. Three-dimensional modelling of auxin flow in the root tip suggests that AUX1-dependent transport through non-hair cells maintains an auxin supply to developing hair cells as they increase in distance from the root tip, and sustains root-hair outgrowth. Experimental data support the hypothesis that instead of moving uniformly though the epidermal cell layer, auxin is mainly transported through canals that extend longitudinally into the tissue.
植物激素生长素以浓度依赖的方式控制根表皮细胞的发育。根毛在一部分表皮细胞上产生，这些细胞随着与根尖距离的增加而增多。生长素是根毛起始和持续生长所必需的，但人们对其在根的该区域中的分布了解甚少。与毛细胞可能需要活跃的生长素内流以确保生长素供应的预期相反，我们在根毛细胞中未检测到生长素内流转运蛋白AUX1。在相邻的非毛细胞列中检测到高水平的AUX1表达。非毛细胞对于达到野生型根毛长度是必需的，尽管这些细胞中不需要生长素响应。根尖生长素流动的三维模型表明，随着发育中的毛细胞与根尖距离的增加，通过非毛细胞的AUX1依赖性运输维持了对它们的生长素供应，并维持根毛的生长。实验数据支持这样的假设，即生长素不是均匀地穿过表皮细胞层，而是主要通过纵向延伸到组织中的通道进行运输。
