氯离子外流通过肌醇3,4,5,6-四磷酸盐调控花粉管的生长和细胞的体积

肌醇盐和Cl-流调控花粉管的生长和细胞的体积      氯离子外流通过肌醇3,4,5,6-四磷酸盐调控花粉管的生长和细胞的体积

p{text-indent:2em; margin:6px 3px 6px 3px; line-height:21px;} 图注： 上图1：Cl-振荡与花粉管生长速率一致。 上图2：肌醇3,4,5,6-四磷酸盐扰乱花粉管尖端的Cl-外流。负值代表外流。 花粉管生长是生物系统中自发组织的一个重要实例。在这些自发系统中，通过交互反馈通路传递信号，从而控制并调整分子及生化参数使之最适于生长和发挥作用。花粉作为一种研究植物细胞发育、生长以及生物生理学的模式材料，发现花粉管的振荡生长与Ca2+、H+、K+三种阳离子振荡内流有关。 在哺乳动物分泌细胞中，Cl-通道作为重要的调节者调控分泌活动并维持细胞体积。已经证明肌醇3,4,5,6-四磷酸盐负调控Ca2+激活Cl-通道。不同的肌醇磷酸盐作用于花粉管时，肌醇3,4,5,6-四磷酸盐的作用最强。 Feijó等研究人员应用非损伤微测技术探索了肌醇3,4,5,6-四磷酸盐和Cl-流之间的潜在关系。研究发现，在烟草和百合花粉管尖端出现振荡的Cl-外流，从距尖端12μm开始沿着花粉管出现持续内流。氯通道阻断剂DIDS（4,4’-diisothiocyanatostilbene-2,2‘-disulfonic acid）和5-硝基-2-(3-苯丙氨基)-苯甲酸（5-nitro-2-(3-phenylpropylamino)benzoic acid）分别在80μM和20μM时能够完全抑制烟草花粉管生长，诱导细胞体积增大，扰乱尖端Cl-外流。另外，肌醇3,4,5,6-四磷酸盐编码的信号不利于花粉管生长，并可诱导细胞体积增大，扰乱正常的Cl-振荡外流。相关分析表明Cl-外流的周期在时间上与生长周期吻合，且生长周期中Cl-外流与囊泡运动有关。 这一研究对于认识调控花粉管平衡和生长网络中的Cl-动力学非常重要。 关键词：花粉管（pollen tube）;Cl-流（Chloride flux）;肌醇3,4,5,6-四磷酸盐（inositol 3,4,5,6-tetra kisphosphate） 参考文献：Laura Zonia, et al. The Plant Cell, 2002, 14: 2233-2249 全文下载：http://www.xuyue.net/xylt/viewthread.php  【转载请注明出处】

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Abstract：

Oscillatory growth of pollen tubes has been correlated with oscillatory influxes of the cations Ca²⁺, H⁺, and K^+. Using an ion-specific vibrating probe, a new circuit was identified that involves oscillatory efflux of the anion Cl^- at the apex and steady influx along the tube starting at 12μm distal to the tip. This spatial coupling of influx and efflux sites predicts that a vectorial flux of Cl^- ion traverses the apical region. The Cl- channel blockers 4,4’-diisothiocyanatostilbene-2,2’-disulfonic acid (DIDS) and 5-nitro-2-(3-phenylpropylamino)benzoic acid completely inhibited tobacco pollen tube growth at 80 and 20μM, respectively. Cl^- channel blockers also induced increases in apical cell volume. The apical 50μm of untreated pollen tubes had a mean cell volume of 3905±75μm³. DIDS at 80μM caused a rapid and lethal cell volume increase to 6206±171μm³, which is at the point of cell bursting at the apex. DIDS was further demonstrated to disrupt Cl- efflux from the apex, indicating that Cl^- flux correlates with pollen tube growth and cell volume status. The signal encoded by inositol 3,4,5,6-tetrakisphosphate [Ins(3,4,5,6)P₄] antagonized pollen tube growth, induced cell volume increases, and disrupted Cl^- efflux. Ins(3,4,5,6)P₄ decreased the mean growth rate by 85%, increased the cell volume to 5997±148μm3, and disrupted normal Cl^- efflux oscillations. These effects were specific for Ins(3,4,5,6)P₄ and were not mimicked by either Ins(1,3,4,5)P₄ or Ins(1,3,4,5,6)P₅. Growth correlation analysis demonstrated that cycles of Cl^- efflux were coupled to and temporally in phase with cycles of growth. A role for Cl^- flux in the dynamic cellular events during growth is assessed. Differential interference contrast microscopy and kymographic analysis of individual growth cycles revealed that vesicles can advance transiently to within 2 to 4μm of the apex during the phase of maximally increasing Cl^- efflux, which temporally overlaps the phase of cell elongation during the growth cycle. In summary, these investigations indicate that Cl^- ion dynamics are an important component in the network of events that regulate pollen tube homeostasis and growth.