百年假说终获解析: 穿梭的LAZY蛋白“唤醒”植物对重力的感应

doi:10.11983/CBB23131

摘要/Abstract

摘要： 植物感受到重力刺激后可通过重力反应协调自身各器官的生长方向。在植物重力反应过程中, 重力感应和信号转导一直都是植物学领域关注的焦点。经典的“淀粉-平衡石”假说认为植物对重力的感应是通过淀粉体(富含淀粉的质体)沉降来实现。此外, 研究发现LAZY蛋白通过调控生长素的不对称分布参与植物重力反应。然而, 淀粉体沉降引发的重力信号转导及其与LAZY蛋白之间协作的分子机制仍不清楚。近期, 清华大学陈浩东研究团队发现重力刺激能够诱导拟南芥(Arabidopsis thaliana) MKK5-MPK3激酶途径, 进而对LAZY蛋白进行磷酸化, LAZY蛋白的磷酸化增强其与淀粉体表面TOC蛋白的互作, 促进LAZY蛋白在淀粉体表面富集。淀粉体沉降引导LAZY蛋白在新的底侧质膜极性再定位。该研究深入解析了植物重力信号转导的分子机制, 建立了植物重力感应与LAZY蛋白介导的生长素不对称分布之间的联系, 是植物向重力性研究领域的重大突破。

关键词: 重力反应, 淀粉体, 极性定位, 磷酸化, “淀粉-平衡石”假说, LAZY, TOC, MPK

Abstract: Plants can coordinate the growth direction of their various organs upon the gravity stimulus. In the process of plant gravitropism, gravity sensing and gravity signal transduction have always been the focus of attention in the field of plants. The classical “starch-statolith” hypothesis proposes that plants sense gravity through the sedimentation of amyloplasts that contain starch granules. In addition, previous studies have shown that LAZY proteins regulate plant gravitropism by mediating the asymmetric distribution of auxin. However, the molecular mechanism underlying how sedimentation of amyloplasts triggers gravity signal transduction and its coordination with LAZY proteins remains unclear. Recently, Professor Haodong Chen’s team from Tsinghua University reveals that gravistimulation induces the phosphorylation of LAZY proteins via MKK5-MPK3 kinase pathway in Arabidopsis, which modulates the phosphorylation of LAZY proteins. The phosphorylated LAZY proteins can enhance their interaction with the TOC proteins on the surface of amyloplasts, leading to the enrichment of LAZY proteins on the surface of amyloplasts and the polarity relocation on the new bottom of plasma membrane. This study illustrates the molecular mechanism underlying gravity signal transduction in plants and establishes the molecular connection between gravity sensing and LAZY mediated auxin asymmetric distribution, which is a major breakthrough in the field of plant gravitropism.

Key words: gravitropism, amyloplast, polar localization, phosphorylation, “starch-statolith” hypothesis, LAZY, TOC, MPK

王文广, 王永红. 百年假说终获解析: 穿梭的LAZY蛋白“唤醒”植物对重力的感应. 植物学报, 2023, 58(5): 677-681.

Wang Wenguang, Wang Yonghong. Century-old Hypothesis Finally Revealed: the Shuttling LAZY Proteins “Awaken” Gravity Sensing in Planta. Chinese Bulletin of Botany, 2023, 58(5): 677-681.

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链接本文: https://www.chinbullbotany.com/CN/10.11983/CBB23131

https://www.chinbullbotany.com/CN/Y2023/V58/I5/677

图/表 1

图1 拟南芥根尖的向重力弯曲以及重力刺激后柱细胞中LAZY4-GFP的荧光分布(图片由陈浩东研究员提供) (A) 将拟南芥LAZY4-GFP/lazy234幼苗在竖直放置的MS培养基上生长4天(持续白光), 然后旋转90o到水平方向进行重力刺激, 重力刺激6小时的根尖表现出明显的向重力弯曲生长(bar=5 mm); (B), (C) 将部分竖直生长的幼苗转移到含有10 μmol?L-1 CHX (蛋白合成抑制剂)的MS培养基上, 并且旋转90o到水平位置进行重力刺激约0.5小时。用共聚焦显微镜采集荧光图片。红色箭头指示淀粉体的位置。白色箭头指示根尖柱细胞中, 下侧细胞膜上与淀粉体邻近的位置有明显的LAZY4-GFP蛋白富集。标有G的箭头表示重力方向。Bars=10 μm

Figure 1 Gravitropism of Arabidopsis root tip and the fluorescence of LAZY4-GFP in the columella cells under gravistimulation (photos provided by Prof. Haodong Chen) (A) Seedlings of LAZY4-GFP/lazy234 were grown vertically on MS plates under white light for 4 days, and then reoriented 90o to the horizontal position for gravistimulation, the root tip showed obvious gravitropic bending after 6 h gravistimulation (bar=5 mm); (B), (C) Some of the vertically growing seedlings were transferred to MS plates with 10 μmol?L-1 CHX (protein synthesis inhibitor) to inhibit protein synthesis, and reoriented 90o to the horizontal position for gravistimulation for around 0.5 h. Fluorescence images were acquired using a confocal microscope. Red arrowheads indicate the amyloplasts. White arrowheads indicate the accumulated signal of LAZY4-GFP on the lower side of plasma membrane adjacent to the amyloplasts in root tip columella cells. Arrows labeled G indicate the direction of gravity. Bars=10 μm

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