Department of Plant Biology, Carnegie Institution for Science, Stanford, CA 94305.
Department of Biology, Stanford University, Stanford, CA 94305.
Proc Natl Acad Sci U S A. 2018 Jan 23;115(4):E822-E831. doi: 10.1073/pnas.1710709115. Epub 2018 Jan 9.
Water availability is a potent regulator of plant development and induces root branching through a process termed hydropatterning. Hydropatterning enables roots to position lateral branches toward regions of high water availability, such as wet soil or agar media, while preventing their emergence where water is less available, such as in air. The mechanism by which roots perceive the spatial distribution of water during hydropatterning is unknown. Using primary roots of (maize) we reveal that developmental competence for hydropatterning is limited to the growth zone of the root tip. Past work has shown that growth generates gradients in water potential across an organ when asymmetries exist in the distribution of available water. Using mathematical modeling, we predict that substantial growth-sustained water potential gradients are also generated in the hydropatterning competent zone and that such biophysical cues inform the patterning of lateral roots. Using diverse chemical and environmental treatments we experimentally demonstrate that growth is necessary for normal hydropatterning of lateral roots. Transcriptomic characterization of the local response of tissues to a moist surface or air revealed extensive regulation of signaling and physiological pathways, some of which we show are growth-dependent. Our work supports a "sense-by-growth" mechanism governing hydropatterning, by which water availability cues are rendered interpretable through growth-sustained water movement.
水的可获得性是植物发育的一个有力调节因子，通过一个称为水力模式的过程诱导根系分枝。水力模式使根能够将侧枝定位在高水可获得性的区域，例如湿土或琼脂培养基，同时防止它们在水可获得性较低的区域出现，例如在空气中。根在水力模式中感知水的空间分布的机制尚不清楚。使用 （玉米）的主根，我们揭示出水力模式形成的发育能力仅限于根尖的生长区。过去的工作表明，当可用水的分布存在不对称时，生长会在器官中产生水势梯度。通过数学建模，我们预测在水力模式形成能力区也会产生大量生长维持的水势梯度，并且这种生物物理线索为侧根的模式形成提供信息。通过使用各种化学和环境处理进行实验，我们证明了生长对于侧根的正常水力模式形成是必要的。对组织对潮湿表面或空气的局部反应的转录组特征分析表明，信号转导和生理途径的广泛调节，其中一些我们表明是依赖于生长的。我们的工作支持了一种“生长感知”机制来控制水力模式形成，其中水可用性线索通过生长维持的水分运动变得可解释。
