摘要：

花粉管是植物有性生殖的重要结构之一,其生长需要精密的细胞内外信号协调。钙离子作为重要的第二信使,在花粉管生长的各个阶段发挥重要作用。钙离子通过离子通道从外部或内源性钙离子库进入细胞质,并通过钙离子泵和转运体被逆向转运出去,以维持钙离子动态平衡。这种钙离子内流与外排的协调调节,是钙离子信号建立与维持的关键。钙依赖蛋白激酶(CPK)和类钙调神经磷酸酶B亚基(CBL)是两类重要的钙离子感受蛋白,它们能够感知细胞内钙离子变化,并通过磷酸化下游靶蛋白调控花粉管的极性生长。具体而言,CBL信号通路通过调节离子平衡和液泡动态来参与调控,而CPK信号通路则通过调节水分通道、一氧化氮合成、离子通道等,影响花粉管的膨压、生长速度和生长方向。这些钙离子信号分子与小G蛋白ROP1及其下游通路之间存在复杂的相互调控关系。综述了钙离子信号在花粉管生长中的关键作用,并阐述了参与钙离子信号调节的蛋白激酶家族及其信号通路的调控机制,为深入理解花粉管极性生长的分子机制提供了重要参考。

关键词: 花粉管, 极性生长, 蛋白激酶, 磷酸化, 钙信号途径

Abstract:

The pollen tube is one of the important structures for plant sexual reproduction,and its growth requires precise coordination of intracellular and extracellular signals.Calcium ions(Ca²⁺)as an important second messenger play a crucial role in various stages of pollen tube growth.Ca²⁺ enters the cytoplasm through ion channels from the external environment or internal calcium stores,and is then transported out of the cell by calcium pumps and exchangers to maintain the dynamic balance of calcium ions.The coordinated regulation of calcium ion influx and efflux is the key to the establishment and maintenance of calcium ion signaling.Calcium-dependent protein kinases(CPKs)and calcineurin B-like proteins(CBLs)are two important classes of calcium-sensing proteins,which can perceive changes in intracellular calcium concentrations and regulate the polar growth of pollen tubes by phosphorylating downstream target proteins.Specifically,the CBL-CIPK signaling pathway may participate in the regulation of ion balance and vacuolar dynamics,while the CPK signaling pathway may affect the turgor pressure,growth rate and direction of the pollen tube by regulating water channels,nitric oxide synthesis,and ion channels.These calcium signaling molecules have complex regulatory relationships with the small G protein ROP1 and its downstream pathways.In summary,this review summarizes the critical role of calcium signaling in pollen tube growth,and elaborates on the regulatory mechanisms of the CPK and CBL-CIPK signaling pathways,providing important references for in-depth understanding of the molecular mechanisms underlying pollen tube polar growth.

Key words: Pollen tube, Polar growth, Protein kinase, Phosphorylation, Ca²⁺ signaling pathway