Kircher Stefan, Schopfer Peter
Department of Molecular Plant Physiology, Faculty of Biology, Albert-Ludwigs-University, Schänzlestr. 1, D-79104 Freiburg, Germany.
Department of Molecular Plant Physiology, Faculty of Biology, Albert-Ludwigs-University, Schänzlestr. 1, D-79104 Freiburg, Germany
J Exp Bot. 2016 Mar;67(5):1411-20. doi: 10.1093/jxb/erv541. Epub 2015 Dec 27.
Branching by de novo formation of lateral roots along the primary root of Arabidopsis seedlings follows a complex longitudinal and transverse pattern. How this pattern is generated is presently under debate. The 'bending hypothesis' proposes that lateral root primordia are initiated by a local accumulation of auxin at the convex side of bends resulting from deflections through obstacles, gravitropic bending, or other means. In contrast, the 'oscillation hypothesis' proposes the existence of an endogenous clock-type oscillator mechanism producing periodic pulses of gene expression in the root tip that determine the future sites of primordium initiation. Here we report physiological experiments dissecting periodic priming signals, pre-disposing the root to rhythmic lateral root formation, from bending-mediated signals responsible for the subsequent positioning of their initiation along the growing root. While the frequency of lateral roots can be promoted by auxin in the mature root, their positioning follows a pre-formed pattern determined by previous bending. Both types of signals turn out to be necessary, complementary components in an integrating concept of lateral root patterning.
拟南芥幼苗主根上通过从头形成侧根进行分支遵循复杂的纵向和横向模式。目前关于这种模式是如何产生的仍存在争议。“弯曲假说”提出，侧根原基是由生长素在因穿过障碍物、重力弯曲或其他方式产生的弯曲凸侧局部积累而启动的。相比之下，“振荡假说”提出存在一种内源性时钟型振荡器机制，在根尖产生周期性的基因表达脉冲，从而决定原基起始的未来位点。在这里，我们报告了生理学实验，剖析了周期性引发信号，这些信号使根易于形成有节奏的侧根，以及弯曲介导的信号，这些信号负责随后侧根起始沿着生长根的定位。虽然生长素可以促进成熟根中侧根的发生频率，但其定位遵循由先前弯曲决定的预先形成的模式。事实证明，这两种信号都是侧根模式形成整合概念中必要的、互补的组成部分。
