Plant Osmosensors

水对植物生长、发育和生态分布以及农业生产的各个方面都至关重要。干旱引发植物的干旱胁迫信号事件，调节基因表达网络和随后的生理和发育过程，减少水分损失。在这些信号事件中，渗透胁迫的初始感知在基因水平上知之甚少。该项目旨在鉴定和研究植物中编码干旱/水传感器的基因及其调控成分。本研究通过对植物水分感受器基因家族的鉴定和研究，不仅可以进一步了解植物对水分的感受机制，而且可以为作物、牧草和树木等耐旱植物的基因工程提供潜在的遗传靶点。渗透胁迫引起细胞内Ca 2+浓度（[Ca 2 +]i）的瞬时升高，其被认为与电子感应有关。然而，相应的光敏感组分的分子性质在很大程度上仍然未知。使用水母发光蛋白Ca 2+成像为基础的无偏正向遗传筛选，拟南芥突变体缺陷的渗透胁迫诱导的[Ca 2 +]i增加（oici）之前被分离，和一个基因，OSCA 1，被确定为一个功能新颖和进化保守的通道蛋白家族的创始成员。OSCA 1在质膜中形成具有Ca 2+渗透性的高渗透压门控非选择性阳离子通道。抑制OSCA 1导致气孔运动和根生长中的渗透信号减弱，表明OSCA 1在植物中起着渗透压传感器的作用。在这个项目中，将确定OSCA 1通道的详细生物物理特性（目标1）。然后，将筛选其他14个OSCA 1同源物的干旱敏感活性（目标2），并评估它们在干旱胁迫和根向水性中的生理功能（目标3）。最后，将通过对另外的oici突变体的精细定位来分离新的反义相关组分（目的4）。该项目将建立Ca 2+介导的感觉机制，植物通过该机制感知外部环境和内部组织中的水分可用性。

Water is crucial to all aspects of plant growth, development and ecological distribution, as well as agricultural production. Drought triggers osmotic-stress signaling events in plants, which regulate the gene expression network and subsequent physiological and developmental processes, reducing water loss. Among these signaling events, the initial perception for osmotic stress is poorly understood at the gene level. The project is designed to identify and study the genes encoding sensors for drought/water as well as their regulatory components in plants. In this project, the identification and examination of the gene family of water sensors will not only further our understanding of how plants sense water, but also provide potential genetic targets for engineering drought resistant plants, such as crops, grasses and trees.It is well established for over the last 20 years that osmotic stress evokes a transient increase in cytosolic Ca2+ concentration ([Ca2+]i), which is thought to be involved in osmosensing. However, the molecular nature of the corresponding osmosensing components remains largely unknown. Using aequorin Ca2+ imaging-based unbiased forward genetic screens, Arabidopsis mutants defective in osmotic stress-induced [Ca2+]i increases (oici) were previously isolated, and one gene, OSCA1, was identified as the founding member of a functionally novel and evolutionarily conserved family of channel proteins. OSCA1 forms hyperosmolality-gated, non-selective cation channels with Ca2+ permeability in the plasma membrane. Suppression of OSCA1 results in attenuated osmotic signaling in stomatal movements and root growth, suggesting that OSCA1 functions as an osmosensor in plants. In this project, the detailed biophysical properties of OSCA1 channels will be determined (Aim 1). Then, 14 other OSCA1 homologs will be screened for their osmosensing activities (Aim 2), and their physiological functions in drought stress and root hydrotropism will be assessed (Aim 3). Finally, novel osmosensing-related components will be isolated via fine-mapping of additional oici mutants (Aim 4). This project will establish the Ca2+-mediated sensory machinery by which plants perceive water availability in both external environments and internal tissues.