LlFH1-mediated interaction between actin fringe and exocytic vesicles is involved in pollen tube tip growth
LlFH1-mediated interaction between actin fringe and exocytic vesicles is involved in pollen tube tip growth
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LlFH1 介导的肌动蛋白边缘和胞吐囊泡之间的相互作用参与花粉管尖端的生长
DOI：
10.1111/nph.14395
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发表时间：
2017-04-01
期刊：
影响因子：
9.4
通讯作者：
Ren, Haiyun
中科院分区：
文献类型：
--
作者：
Li, Shanwei;Dong, Huaijian;Ren, Haiyun
花粉管顶端生长是细胞极化生长的一种极端形式，它需要基于动态肌动蛋白细胞骨架的极化胞吐作用。然而，肌动蛋白丝和胞吐囊泡之间的联系的分子基础还不清楚。在这里，我们确定了百合花粉特异性蛋白酶（LIFH1），并发现它定位于顶端囊泡和质膜（PM）。LlFH 1的过表达诱导管尖端区域出现过多的肌动蛋白索，而LlFH 1的下调则消除了肌动蛋白边缘。荧光恢复后的光漂白（FRAP）分析表明，LIFH1标记的胞吐囊泡表现出在顶点的肩膀处的初始积累，并与肌动蛋白条纹的前缘相吻合。延时分析表明，肌动蛋白丝的形成是伴随着顶端囊泡的出现而发生的，说明LIFH 1可以启动肌动蛋白的聚合，生化分析表明LIFH 1 FH1 FH2可以使肌动蛋白聚合成核，但在有倒刺的一端将肌动蛋白丝封端并抑制其伸长。而在百合profilins存在下，LIFH1 FH1 FH2可促进刺端肌动蛋白的伸长。另外，LIFH1 FH1 FH2还能使肌动蛋白丝成束，因此我们推测，在百合花粉管生长过程中，LIFH1和profilin协调肌动蛋白丝与胞吐小泡运输之间的相互作用。
Pollen tube tip growth is an extreme form of polarized cell growth, which requires polarized exocytosis based on a dynamic actin cytoskeleton. However, the molecular basis for the connection between actin filaments and exocytic vesicles is unclear.Here, we identified a Lilium longiflorum pollen-specific formin (LlFH1) and found that it localized at the apical vesicles and plasma membrane (PM). Overexpression of LlFH1 induced excessive actin cables in the tube tip region, and downregulation of LlFH1 eliminated the actin fringe. Fluorescence recovery after photobleaching (FRAP) analysis revealed that LlFH1-labeled exocytic vesicles exhibited an initial accumulation at the shoulder of the apex and coincided with the leading edge of the actin fringe. Time-lapse analysis suggested that nascent actin filaments followed the emergence of the apical vesicles, implying that LlFH1 at apical vesicles could initiate actin polymerization.Biochemical assays showed that LlFH1 FH1FH2 could nucleate actin polymerization, but then capped the actin filament at the barbed end and inhibited its elongation. However, in the presence of lily profilins, LlFH1 FH1FH2 could accelerate barbed-end actin elongation. In addition, LlFH1 FH1FH2 was able to bundle actin filaments.Thus, we propose that LlFH1 and profilin coordinate the interaction between the actin fringe and exocytic vesicle trafficking during pollen tube growth of lily.