Type B Phosphatidylinositol-4-Phosphate 5-Kinases Mediate Arabidopsis and Nicotiana tabacum Pollen Tube Growth by Regulating Apical Pectin Secretion
Type B Phosphatidylinositol-4-Phosphate 5-Kinases Mediate Arabidopsis and Nicotiana tabacum Pollen Tube Growth by Regulating Apical Pectin Secretion
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DOI：
10.1105/tpc.108.059568
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发表时间：
2008-12-01
期刊：
影响因子：
11.6
通讯作者：
Heilmann, Ingo
中科院分区：
文献类型：
--
作者：
Ischebeck, Till;Stenzel, Irene;Heilmann, Ingo
磷脂酰肌醇 4,5-二磷酸 [PtdIns(4,5)P-2] 存在于生长的花粉管的顶端质膜中。由于负责在该位置产生 PtdIns(4,5) P-2 的酶尚未得到表征，因此 PtdIns(4,5) P-2 在花粉管尖端生长中的功能尚未确定。鉴定了编码拟南芥B亚科花粉表达的拟南芥磷脂酰肌醇-4-磷酸5-激酶（PI4P 5-激酶）的两个候选基因（PIP5K4和PIP5K5），其重组蛋白被鉴定为PI4P 5-激酶。缺乏 PIP5K4 和 PIP5K5 的 T-DNA 插入系的花粉表现出花粉萌发减少和花粉管伸长缺陷。荧光标记的 PIP5K4 和 PIP5K5 定位于拟南芥和烟草 (Nicotiana tabacum) 花粉管的顶端质膜微区，PIP5K4 或 PIP5K5 的过度表达触发了多个顶端分支事件。使用烟草系统的进一步研究表明，过度表达导致大量顶端果胶沉积，并伴有质膜内陷。相比之下，过表达细胞中的胼胝质沉积和细胞骨架结构没有改变。形态效应取决于 PtdIns(4,5) P-2 的产生，因为无活性的酶变体不会产生任何效应。数据表明，B 型 PI4P 5-激酶产生过多的 PtdIns(4,5) P2 会扰乱膜运输和顶端果胶沉积的平衡。因此，PtdIns(4,5) P-2 可能通过对膜运输和/或顶端果胶沉积的调节作用来调节花粉管极尖的生长。
Phosphatidylinositol-4,5-bisphosphate [PtdIns(4,5)P-2] occurs in the apical plasma membrane of growing pollen tubes. Because enzymes responsible for PtdIns(4,5) P-2 production at that location are uncharacterized, functions of PtdIns( 4,5) P-2 in pollen tube tip growth are unresolved. Two candidate genes encoding pollen-expressed Arabidopsis thaliana phosphatidylinositol-4-phosphate 5-kinases (PI4P 5-kinases) of Arabidopsis subfamily B were identified (PIP5K4 and PIP5K5), and their recombinant proteins were characterized as being PI4P 5-kinases. Pollen of T-DNA insertion lines deficient in both PIP5K4 and PIP5K5 exhibited reduced pollen germination and defects in pollen tube elongation. Fluorescence-tagged PIP5K4 and PIP5K5 localized to an apical plasma membrane microdomain in Arabidopsis and tobacco (Nicotiana tabacum) pollen tubes, and overexpression of either PIP5K4 or PIP5K5 triggered multiple tip branching events. Further studies using the tobacco system revealed that overexpression caused massive apical pectin deposition accompanied by plasma membrane invaginations. By contrast, callose deposition and cytoskeletal structures were unaltered in the overexpressors. Morphological effects depended on PtdIns(4,5) P-2 production, as an inactive enzyme variant did not produce any effects. The data indicate that excessive PtdIns(4,5) P2 production by type B PI4P 5-kinases disturbs the balance of membrane trafficking and apical pectin deposition. Polar tip growth of pollen tubes may thus be modulated by PtdIns(4,5) P-2 via regulatory effects on membrane trafficking and/or apical pectin deposition.