Reevaluation of the role of chloroplasts in the calsium signaling in guard cells

重新评估叶绿体在保卫细胞钙信号传导中的作用

基本信息

批准号：
18570048
负责人：
SHIINA Takashi
金额：
$ 2.57万
依托单位：
Kyoto Prefectural University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2006
资助国家：
日本
起止时间：
2006 至 2007
项目状态：
已结题

项目摘要

The role of guard cell chloroplasts in stomatal function is controversial. It is usually assumed that stomatal closure is preceded by a transient increase in cytosolic free Ca^<2+> concentration (Ca^<2+>)_<cyt>) in the guard cells. CAS (Ca^<2+> sensing receptor) is a plant-specific putative Ca^<2+>-binding protein. We foundthat CAS is an integral thylakoid membrane protein, and the N-terminus acidic Ca^<2+>-binding region is likely exposed to the stromal side of the membrane. CAS is essential for stomatal closure induced by external Ca^<2+>. These results provide the evidence that chloroplasts play a critical role in the generation of extracellular Ca^<2+>([Ca^<2+>]_<ext>)-induced[Ca^<2+>]_<cyt> transients and stomatal closure in Arabidopsis.In addition, we founs that extracellular abiotic and pathogen-related stress signals are relayed quickly to chloroplasts, and evoke rapid and transient increases in stromal Ca^<2+> concentration in a stress-dependent manner. Furthermore we demonstrated that CAS is also related to the generation of stromal Ca2+ transients induced by pathogen elicitors and/or light to dark transition. Furthermore, we demonstrated that CAS regulates a multitude of plant innate immune responses, such as flg22-induced stomatal closure, expression of pathogen-related genes, ROS production and a resistance (R) gene-triggered hypersensitive cell death in Arabidopsis. It should be noted that cas-1 shows no significant growth phenotype. These results may have implications for a far more important role of chloroplasts in the regulation of plant innate immune response than was thought.

防护细胞叶绿体在气孔功能中的作用是有争议的。通常假定在护罩细胞中，气孔闭合是在胞质游离Ca^<2+>浓度（Ca^<2+>）_ <cyt>上的瞬时增加。 CAS（Ca^<2+>传感受体）是一种植物特异性的Ca^<2+> - 结合蛋白。我们发现CAS是一种积分的类囊体膜蛋白，N-末端酸性Ca^<2+> - 结合区可能暴露于膜的基质侧。 CAS对于外部Ca^<2+>引起的气孔闭合至关重要。这些结果提供了一个证据，表明叶绿体在产生细胞外Ca^<2+>（[[Ca^<2+>] _ <ext>） - 诱导的[Ca^<2+>] _ <cyt>瞬态和气孔闭合，并在拟南芥中进行了闭合。瞬态以应力依赖性方式增加基质Ca^<2+>浓度。此外，我们证明了CAS还与病原体引起者和/或光到黑暗过渡引起的基质Ca2+瞬变的产生有关。此外，我们证明CAS调节了多种植物先天免疫反应，例如FLG22诱导的气孔闭合，病原体相关基因的表达，ROS产生和抗拟南芥的抗性（R）基因触发的超敏细胞死亡。应当指出的是，CAS-1没有明显的生长表型。这些结果可能对叶绿体在调节植物先天免疫反应中的重要作用可能比想象的要重要得多。