Department of Plant Biology, Carnegie Institution for Science, Stanford, CA 94305;Temasek Lifesciences Laboratory, National University of Singapore, Singapore 117604;Department of Biological Sciences, National University of Singapore, Singapore 117543;
Temasek Lifesciences Laboratory, National University of Singapore, Singapore 117604;
Proc Natl Acad Sci U S A. 2014 Jun 24;111(25):9319-24. doi: 10.1073/pnas.1400966111. Epub 2014 Jun 9.
The architecture of the branched root system of plants is a major determinant of vigor. Water availability is known to impact root physiology and growth; however, the spatial scale at which this stimulus influences root architecture is poorly understood. Here we reveal that differences in the availability of water across the circumferential axis of the root create spatial cues that determine the position of lateral root branches. We show that roots of several plant species can distinguish between a wet surface and air environments and that this also impacts the patterning of root hairs, anthocyanins, and aerenchyma in a phenomenon we describe as hydropatterning. This environmental response is distinct from a touch response and requires available water to induce lateral roots along a contacted surface. X-ray microscale computed tomography and 3D reconstruction of soil-grown root systems demonstrate that such responses also occur under physiologically relevant conditions. Using early-stage lateral root markers, we show that hydropatterning acts before the initiation stage and likely determines the circumferential position at which lateral root founder cells are specified. Hydropatterning is independent of endogenous abscisic acid signaling, distinguishing it from a classic water-stress response. Higher water availability induces the biosynthesis and transport of the lateral root-inductive signal auxin through local regulation of tryptophan aminotransferase of Arabidopsis 1 and PIN-formed 3, both of which are necessary for normal hydropatterning. Our work suggests that water availability is sensed and interpreted at the suborgan level and locally patterns a wide variety of developmental processes in the root.
植物分枝根系结构是活力的主要决定因素。人们已知水的可获得性会影响根系生理学和生长；然而，这种刺激影响根系结构的空间尺度仍了解甚少。在这里，我们揭示了根圆周轴上水分可获得性的差异会产生空间线索，从而决定侧根分支的位置。我们表明，几种植物的根可以区分潮湿表面和空气环境，并且这种差异也会影响根毛、花青苷和通气组织的模式，我们将这种现象描述为水力模式。这种环境反应与触摸反应不同，需要可用水才能在接触表面诱导侧根。对土壤中生长的根系进行的 X 射线微尺度计算机断层扫描和 3D 重建表明，在生理相关条件下也会发生这种反应。使用早期侧根标记物，我们表明水力模式在起始阶段之前起作用，并且可能决定侧根创始细胞指定的圆周位置。水力模式独立于内源性脱落酸信号，使其有别于经典的水分胁迫反应。较高的水可用性通过局部调节拟南芥 1 的色氨酸转氨酶和 PIN 形成 3 诱导侧根诱导信号生长素的生物合成和运输，这两者对于正常的水力模式都是必需的。我们的工作表明，水的可获得性在亚器官水平被感知和解释，并在根中局部模式化各种发育过程。
