Calcium Regulation of Cytokinin-Stimulated Morphogenesis in Plant Cells

了解细胞分裂素（n6 -取代腺嘌呤）对植物细胞分裂的控制作为植物细胞调控的模型变得越来越重要。先前关于细胞分裂素诱导的目标苔藓茎突细胞不对称分裂的研究表明，细胞内钙离子浓度的空间控制上升是激活钙调蛋白的第二信使。提出了细胞分裂素刺激细胞分裂的模型，该模型表明细胞分裂素与靶细胞上不对称定位的质膜受体的结合增加了细胞内和细胞外的钙储存，导致钙依赖性蛋白激酶激活和蛋白质磷酸化/去磷酸化。细胞内钙和蛋白磷酸化的时空变化似乎都与激素治疗后的细胞质重排有关。通过磷酸化对预先存在的蛋白质进行共价修饰是调节细胞生长和分化的主要机制，这一点越来越清楚。钙和蛋白磷酸化可能在细胞分裂素控制细胞功能中起协同作用。当前项目的目标是：1。利用8-叠氮基苄基腺嘌呤进行光亲和标记，表征细胞分裂素结合位点。使用针对细胞分裂素的抗体分析细胞分裂素结合的定位，2。3 .利用金属色指标分析钙摄取；监测激素治疗后的细胞骨架重排、离子变化和磷酸化模式。这项研究将增加我们对细胞分裂素信号传导的理解，钙的第二信使作用，以及通过蛋白质磷酸化放大细胞反应导致植物发育变化。

Understanding the control of cell division in plants by cytokinins (N6-substituted adenines) is becoming increasingly important as a model for cellular regulation in plants. Previous research on cytokinin-induced asymmetrical division in target caulonema cells of the moss Funaria has implicated a spatially controlled rise in intracellular calcium ion concentration as a second messenger that activates calmodulin. A model for cytokinin stimulation of cell division is proposed that suggests that the binding of cytokinin to asymmetrically localized plasma membrane receptors on target cells increases intracellular calcium from both intracellular and extracellular stores leading to calcium-dependent protein kinase activation and protein phosphorylation/dephosphorylation. Both the spatial and temporal changes in intracellular calcium and the protein phosphorylation appear to be involved in the profound cytoplasmic rearrangements seen after hormone treatment. It is becoming increasingly clear that covalent modification of preexisting proteins by phosphorylation is a major mechanism in the regulation of cell growth and differentiation. Calcium and protein phosphorylation may play a synergistic role in cytokinin control of cellular function. The goals of the current project are to: 1. characterize cytokinin binding sites by photoaffinity labeling using 8-azido benzyladenine, 2. analyze the localization of cytokinin binding using antibodies directed against cytokinins, 3. analyze calcium uptake using metallochromic indicators, and 4. monitor the cytoskeletal rearrangements, ion changes and phosphorylation patterns after hormone treatment. This research will increase our understanding of cytokinin signalling, the second messenger role of calcium, and the amplification of cellular response by protein phosphorylation leading to developmental changes in plants.