Molecular mechanisms of root gravity sensing and signal transduction
Molecular mechanisms of root gravity sensing and signal transduction
复制标题
DOI：
10.1002/wdev.14
复制
发表时间：
2012-03-01
影响因子：
--
通讯作者：
Masson, Patrick H.
中科院分区：
文献类型：
--
作者：
Strohm, Allison K.;Baldwin, Katherine L.;Masson, Patrick H.
植物利用重力引导它们的根进入土壤中，以锚住自己，并找到生长和发育所需的资源。在高等植物中，根尖的柱细胞形成重力感应的主要场所，并且在这些细胞中，致密的、充满淀粉的质体（造淀粉体）的沉积触发重力信号转导。这在根冠上产生了一个生长素梯度，它被传递到伸长区，在那里它促进了细胞的差异伸长，使根能够向下定向。淀粉体的沉积如何导致生长素的再分布，目前还不清楚。已经提出模型来解释机械敏感离子通道或配体受体相互作用如何连接这些事件。虽然它们的作用还不清楚，但在这一过程中可能的第二信使包括质子，Ca 2+和肌醇1，4，5-三磷酸。在重力刺激下，生长素流出促进剂PIN 3和PIN 7重新定位于柱细胞的下侧并介导生长素重新分布。然而，生长素独立的重力感应和信号转导的二级机制的证据表明，这一生理过程是相当复杂的。此外，植物必须整合各种环境线索，导致向重力性和其他定向生长反应（如向水性、向光性和向触性）之间的多方面关系。(C)2011 Wiley Periodicals，Inc.
Plants use gravity as a guide to direct their roots down into the soil to anchor themselves and to find resources needed for growth and development. In higher plants, the columella cells of the root tip form the primary site of gravity sensing, and in these cells the sedimentation of dense, starch-filled plastids (amyloplasts) triggers gravity signal transduction. This generates an auxin gradient across the root cap that is transmitted to the elongation zone where it promotes differential cell elongation, allowing the root to direct itself downward. It is still not well understood how amyloplast sedimentation leads to auxin redistribution. Models have been proposed to explain how mechanosensitive ion channels or ligand receptor interactions could connect these events. Although their roles are still unclear, possible second messengers in this process include protons, Ca2+, and inositol 1,4,5-triphosphate. Upon gravistimulation, the auxin efflux facilitators PIN3 and PIN7 relocalize to the lower side of the columella cells and mediate auxin redistribution. However, evidence for an auxin-independent secondary mechanism of gravity sensing and signal transduction suggests that this physiological process is quite complex. Furthermore, plants must integrate a variety of environmental cues, resulting in multifaceted relationships between gravitropism and other directional growth responses such as hydro-, photo-, and thigmotropism. (C) 2011 Wiley Periodicals, Inc.