Laboratory of Genetics, University of Wisconsin-Madison, 425G Henry Mall, Madison, WI 53706, USA.
Laboratory of Genetics, University of Wisconsin-Madison, 425G Henry Mall, Madison, WI 53706, USA; Program in Plant Breeding and Plant Genetics, University of Wisconsin-Madison, Madison, WI, USA.
Curr Biol. 2017 Sep 11;27(17):R964-R972. doi: 10.1016/j.cub.2017.07.015.
Plant shoots typically grow against the gravity vector to access light, whereas roots grow downward into the soil to take up water and nutrients. These gravitropic responses can be altered by developmental and environmental cues. In this review, we discuss the molecular mechanisms that govern the gravitropism of angiosperm roots, where a physical separation between sites for gravity sensing and curvature response has facilitated discovery. Gravity sensing takes place in the columella cells of the root cap, where sedimentation of starch-filled plastids (amyloplasts) triggers a pathway that results in a relocalization to the lower side of the cell of PIN proteins, which facilitate efflux of the plant hormone auxin efflux. Consequently, auxin accumulates in the lower half of the root, triggering bending of the root tip at the elongation zone. We review our understanding of the molecular mechanisms that control this process in primary roots, and discuss recent insights into the regulation of oblique growth in lateral roots and its impact on root-system architecture and soil exploration.
植物的茎通常逆重力方向生长以获取光照，而根则向下生长进入土壤以吸收水分和养分。这些向地性反应可以通过发育和环境线索来改变。在这篇综述中，我们讨论了调控被子植物根向地性的分子机制，在这种机制中，重力感应和弯曲响应位点的物理分离促进了发现。重力感应发生在根冠的柱形细胞中，在这里，充满淀粉的质体（淀粉体）的沉降触发了一个途径，导致 PIN 蛋白重新定位到细胞的下侧，从而促进植物激素生长素的外排。因此，生长素在根的下半部分积累，在伸长区触发根尖的弯曲。我们回顾了我们对控制这一过程的分子机制的理解，并讨论了最近对侧根斜向生长的调控及其对根系结构和土壤探索的影响的新见解。
