Arabidopsis RhoGDIs Are Critical for Cellular Homeostasis of Pollen Tubes
Arabidopsis RhoGDIs Are Critical for Cellular Homeostasis of Pollen Tubes
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DOI：
10.1104/pp.15.01600
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发表时间：
2016-02-01
期刊：
影响因子：
7.4
通讯作者：
Zhang, Yan
中科院分区：
文献类型：
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作者：
Feng, Qiang-Nan;Kang, Hui;Zhang, Yan
Rhos of plants（ROPs）通过调控细胞内肌动蛋白微丝的动态聚合等一系列细胞内活动，在植物细胞形态建成中发挥重要作用，特别是在顶端生长的花粉管和根毛中。ROP受鸟嘌呤核苷酸交换因子（RopGEF）、GTP酶激活蛋白（RopGAP）和鸟嘌呤核苷酸解离抑制剂（RhoGDI）调节。RopGEF和RopGAP在ROP信号传导中发挥进化保守的功能。相比之下，虽然植物RhoGDIs调节ROP的膜提取和细胞质螯合，但不太清楚它们在ROP信号传导中的积极作用，就像它们的酵母和后生动物对应物一样。我们在这里报告，所有三个拟南芥（拟南芥）的GDI（三-GDI）的功能丧失显着降低男性传输由于受损的花粉管生长在体外和体内。我们证明，ROPs异位激活的侧质膜的tri-gdi花粉管。然而，在tri-gdi突变体中，总ROP在后期降低，导致总体抑制的ROP信号传导。事实上，不能与GDI相互作用的R 0 P5突变体不能诱导生长，表明R 0 P-GDI相互作用对于ROP信号传导的重要性。GDIs的功能丧失损害了细胞内稳态，导致花粉管中壁组分的过量顶端积累，类似于异位磷脂酰肌醇4，5-二磷酸信号传导。GDIs和磷脂酰肌醇4，5-二磷酸可能拮抗协调，以维持细胞内稳态在花粉管生长。因此，我们的研究结果表明，一个更复杂的作用，GDI在ROP介导的花粉管生长。
Rhos of plants (ROPs) play a key role in plant cell morphogenesis, especially in tip-growing pollen tubes and root hairs, by regulating an array of intracellular activities such as dynamic polymerization of actin microfilaments. ROPs are regulated by guanine nucleotide exchange factors (RopGEFs), GTPase activating proteins (RopGAPs), and guanine nucleotide dissociation inhibitors (RhoGDIs). RopGEFs and RopGAPs play evolutionarily conserved function in ROP signaling. By contrast, although plant RhoGDIs regulate the membrane extraction and cytoplasmic sequestration of ROPs, less clear are their positive roles in ROP signaling as do their yeast and metazoan counterparts. We report here that functional loss of all three Arabidopsis (Arabidopsis thaliana) GDIs (tri-gdi) significantly reduced male transmission due to impaired pollen tube growth in vitro and in vivo. We demonstrate that ROPs were ectopically activated at the lateral plasma membrane of the tri-gdi pollen tubes. However, total ROPs were reduced posttranslationally in the tri-gdi mutant, resulting in overall dampened ROP signaling. Indeed, a ROP5 mutant that was unable to interact with GDIs failed to induce growth, indicating the importance of the ROP-GDI interaction for ROP signaling. Functional loss of GDIs impaired cellular homeostasis, resulting in excess apical accumulation of wall components in pollen tubes, similar to that resulting from ectopic phosphatidylinositol 4,5-bisphosphate signaling. GDIs and phosphatidylinositol 4,5-bisphosphate may antagonistically coordinate to maintain cellular homeostasis during pollen tube growth. Our results thus demonstrate a more complex role of GDIs in ROP-mediated pollen tube growth.