植物细胞响应重力变化的Ca^(2+)信号

Altered Gravity Induced Ca^(2+) Signal in Plant Cells

重力大小的改变(微重力和超重力)可以对植物的生长发育、生理生化特性、细胞超微结构、基因和蛋白的表达等产生广泛的影响,而Ca^(2+)可能在此过程中起信号物质的作用.重力刺激在植物细胞中引发事件的顺序可能是:重力刺激的感受—细胞膜系统张力改变—膜理化特性改变—膜透性、离子转运、膜连接酶活性等改变—Ca^(2+)信号的产生和转导—新陈代谢变化—生理反应.植物对重力水平变化应激响应的至关重要一步是引起细胞内Ca^(2+)分布区域和浓度的变化,这是将细胞外重力刺激转换为细胞内化学信号的关键步骤.由于机械力敏感的C^(2+)通道的活化和Ca^(2+)-ATPase酶活性受到抑制,重力改变时细胞质中自由Ca^(2+)浓度增加,随后Ca^(2+)作为第二信使介导相关酶活性发生改变,最终引起一连串的生理生化反应.本文探讨了重力变化对植物细胞质内自由Ca^(2+)浓度的影响、Ca^(2+)信号的产生机制.以及Ca^(2+)作为次级信号对细胞生理生化过程调节作用的途径和机制,介绍了常用的Ca^(2+)研究方法,并分析了研究的关键点和难点.

Altered gravity（microgravity and hypergravity） could affect many aspects of plants, such as growth,development,metabolism,ultrastructure,gene and protein expression.Ca^2＋ might play a role as a signal molecular in such graviresponses of plant.We supposed that the consequence of events occurring in plant cells under altered gravity were in the following order：gravisensing—changes in the cytoplasmic membrane surface tension—alterations in the physicochemical properties of the membrane—changes in membrane permeability,ion transport,membrane-bound enzyme activity etc—Ca^2＋ signaling—metabolism rearrangements—physiological responses.Under altered gravity, the intracellular Ca^2＋ balance was redistributed and the increased cytosolic Ca^2＋ concentration was the key step of transforming altered gravity stimulation into intracellular Ca^2＋ signal.Ca^2＋ influx into the cytosol was via activation of Ca^2＋ selective ion channels and inhibition of Ca^2＋-ATPases. Following the increased cytosolic Ca^2＋ concentration,altered gravity induced a series of biological effects by regulating enzyme activity,with involvement of regulatory Ca^2＋ messenger system.This paper summarized the influences of altered gravity on plant intracellular Ca^2＋ balance and discussed the possible pathways of Ca^2＋ influx/efflux and Ca^2＋ signaling in plant cell biochemical regulation to altered gravity.