百合花粉管中的胞吞/胞吐作用观察分析

Visualization of the Endo/Exocytosis in Lily Pollen Tubes

应用细胞膜染料FM4-64结合Zeiss 5 live快速扫描型共聚焦显微镜观察了百合花粉管中的吞排作用.结果显示,培养基中加入FM4-64后,染料迅速进入到花粉管中,并在花粉管顶端形成一个锥形的区域;锥形区域表现出周期性变化,并且与花粉管脉冲生长呈负相关,即锥形区形成期花粉管生长缓慢,而锥形区消退期花粉管生长迅速;在锥形区域的消退期,花粉管顶端,尤其是最顶端快速向前延伸,而在锥形区域的形成期,花粉管最顶端的延伸速度显著下降,但亚顶端区域仍基本维持原有的生长速度.研究发现,花粉管的最顶端既是内吞作用也是胞吐作用的主要场所,但胞吞作用仅局限于花粉管的最顶端,而胞吐作用发生在包括亚顶端在内的整个花粉管顶端;胞吞和胞吐作用在花粉管最顶端交替发生,可能是花粉管脉冲生长的一个非常重要的原因.

Using FM4-64,endo/exocytosis in lily pollen tubes was observed under Zeiss 5 live laser scanning confocal microscope.The data indicated that FM4-64 quickly entered pollen tubes via endocytosis at the apex of pollen tubes,finally forming a V-shaped pattern in the ＂clear zone＂.Time-lape images revealed that the V-shaped pattern FM4-64 showed recurrent changes.Further measurement revealed that pollen tubes grew at an average speed of about 130～200 nm/s during V-shape fading stages,and the data reduced to 50～80 nm/s during V-shape formation stages.Analysis on the outline of the tip of pollen tube during oscillatory growth showed that the elongation of pollen tubes during V-shape fading stages mainly occured at the apex,forming a prolonged half-ball shape at the tip of pollen tubes.On the other hand,during V-shape formation stages,the whole tip of pollen tube elongated slowly,forming a half-ball shape at the tip of pollen tube.All these data enable us to conclude that endocytosis occurs at the extreme apex of the tube dome,while exocytosis occurs at the whole tip of pollen tubes,but mainly at the extreme apex of pollen tubes.Alternant endocytosis and exocytosis occurring at the apex of pollen tubes may answer for the pulsate growth of lily pollen tubes.