Redistribution of actin, profilin and phosphatidylinositol-4,5-bisphosphate in growing and maturing root hairs
Redistribution of actin, profilin and phosphatidylinositol-4,5-bisphosphate in growing and maturing root hairs
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DOI：
10.1007/s004250050746
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发表时间：
1999-10-01
期刊：
影响因子：
4.3
通讯作者：
Menzel, D
中科院分区：
文献类型：
--
作者：
Braun, M;Baluska, F;Menzel, D
在根毛发生和根尖生长过程中，极性细胞质组织的不断变化反映在细胞骨架元素的动态再分布上。小G-肌动蛋白结合蛋白，profilin，这是已知的是一个广泛表达的，有效的调节肌动蛋白动力学，是专门定位在根尖的根毛和共分布的肌动蛋白的弥漫荧光顶帽，但不与subapical肌动蛋白微丝（MF）束。Profilin和肌动蛋白帽是专门存在于凸出的生长根毛和在伸长根毛的顶点;都消失时，尖端生长终止，表明尖端生长机制，涉及profilin-肌动蛋白相互作用的交付和本地化的分泌囊泡的胞吐。磷脂酰肌醇-4，5-二磷酸（PIP 2），profilin的配体，几乎只局限于凸起，随后，形成了一个弱的尖端到基部的梯度在伸长的根毛。当尖端生长被MF破坏抑制剂细胞松弛素D消除时，顶端profilin和肌动蛋白荧光丢失。已知Mastoparan可能通过刺激磷脂酶影响PIP 2周期，导致形成不同肌动蛋白MF的网状结构，取代弥漫性顶端肌动蛋白帽，伴随着尖端生长停止。这表明mastoparan干扰PIP 2调节的profilinactin相互作用，因此干扰了维持根毛尖端生长所必需的条件。
The continuously changing polar cytoplasmic organization during initiation and tip growth of root hairs is reflected by a dynamic redistribution of cytoskeletal elements. The small G-actin binding protein, profilin, which is known to be a widely expressed, potent regulator of actin dynamics, was specifically localized at the tip of root hairs and co-distributed with a diffusely fluorescing apical cap of actin, but not with subapical actin microfilament (MF) bundles. Profilin and actin caps were present exclusively in the bulge of outgrowing root hairs and at the apex of elongating root hairs; both disappeared when tip growth terminated, indicating a tip-growth mechanism that involves profilin-actin interactions for the delivery and localized exocytosis of secretory vesicles. Phosphatidylinositol-4,5-bisphosphate (PIP2), a ligand of profilin, was localized almost exclusively in the bulge and, subsequently, formed a weak tip-to-base gradient in the elongating root hairs. When tip growth was eliminated by the MF-disrupting inhibitor cytochalasin D, the apical profilin and the actin fluorescence were lost. Mastoparan, which is known to affect the PIP2 cycle, probably by stimulating phospholipases, caused the formation of a meshwork of distinct actin MFs replacing the diffuse apical actin cap and, concomittantly, tip growth stopped. This suggests that mastoparan interferes with the PIP2-regulated profilinactin interactions and hence disturbs conditions indispensable for the maintenance of tip growth in root hairs.