As a possible peptide primary messenger, extracellular calmodulin (CaM) may regulate processes such as cell proliferation, pollen germination and expression of some genes. Stomata open or close quickly in response to environmental stimuli. CaM was found to be extracellular both in guard cells of broad bean leaves and in epidermal cells by immuno_electron microscopy and immuno_fluorescence microscopy techniques. Exogenous purified CaM enhanced stomatal closure and inhibited stomatal opening with an optimal concentration of 10-8 mol/L; CaM antagonist W7_agarose and anti_CaM serum, which were membrane_impermeable macromolecules, inhibited stomatal closure and promoted stomatal opening. All these data showed that endogenous extracellular CaM of guard cells did promote stomatal closure and inhibit stomatal opening, and could be active only outside the cells. Therefore under natural conditions, the endogenous extracellular CaM of guard cells might regulate stomatal movements as a primary messenger together with other signal molecules, and might be an important linkage between environmental stimuli and cell responses.
蚕豆下表皮细胞外钙调素的存在及其对气孔运动的调节
陈玉玲 张学琴 陈珈 王学臣*
中国农业大学生物学院，植物生理生化国家重点实验室，北京 100094
细胞外钙调素可能作为多肽第一信使，调节细胞增殖、花粉萌发、特定基因表达等生理过程。气孔能灵敏地对外界刺激作出反应，快速开闭。本文用免疫电镜和免疫荧光显微镜技术证明保卫细胞及其它表皮细胞胞外都存在钙调素。外源纯化钙调素能促进气孔关闭、抑制气孔开放，最适浓度为10-8 mol/L；不能透过质膜的大分子钙调素拮抗剂W7-agarose和钙调素抗血清都能抑制气孔关闭、促进开放，说明保卫细胞的内源胞外钙调素确实能促进气孔关闭、抑制开放，而且只能在细胞外起作用。推测在自然情况下，保卫细胞内源胞外钙调素可能作为胞外第一信使和其它信号分子一起调节气孔的开关运动，而且可能在环境刺激与细胞响应之间起重要作用。
关键词： 细胞外钙调素；蚕豆；气孔运动
通讯作者E-mail：xcwang@public.bta.net.cn
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