Department of Molecular Plant Physiology, Faculty of Biology, University of Freiburg, Schänzlestr. 1, 79104 Freiburg, Germany.
Curr Biol. 2023 Jun 5;33(11):2201-2212.e3. doi: 10.1016/j.cub.2023.04.061. Epub 2023 May 18.
The development of plant roots is subject to control by light. Here, we show that, similar to monotonous root elongation, the periodic induction of lateral roots (LRs) depends on the activation by light of photomorphogenic and photosynthetic photoreceptors in the shoot in a hierarchical order. The prevailing belief is that the plant hormone auxin serves as a mobile signal transmitter, responsible for interorgan communication, including light-controlled shoot-to-root connections. Alternatively, it has been proposed that the transcription factor HY5 assumes the role as a mobile shoot-to-root signal transmitter. Here, we provide evidence that photosynthetic sucrose produced in the shoot acts as the long-distance signal carrier regulating the local, tryptophan-based biosynthesis of auxin in the LR generation zone of the primary root tip, where the LR clock controls the pace of LR initiation in an auxin-tunable manner. Synchronization of LR formation with primary root elongation allows the adjustment of overall root growth to the photosynthetic performance of the shoot and the maintenance of a constant LR density during light-dark changes in a variable light environment.
植物根系的发育受光的控制。在这里，我们表明，类似于单调的根伸长，侧根（LR）的周期性诱导也依赖于光在分层顺序下激活地上部的光形态发生和光合光受体。普遍的观点认为，植物激素生长素作为一种移动信号转导物，负责器官间的通讯，包括光控地上部-根部的连接。或者，有人提出转录因子 HY5 充当移动的地上部-根部信号转导物。在这里，我们提供的证据表明，在地上部产生的光合蔗糖作为远距离信号载体，调节主根尖 LR 发生区中色氨酸为基础的生长素的局部生物合成，其中 LR 时钟以生长素可调的方式控制 LR 起始的速度。LR 形成与主根伸长的同步允许根据地上部的光合作用性能调整整体根生长，并在可变光照环境中光-暗变化期间维持恒定的 LR 密度。
