Eukaryotic cells rely on the accuracy and efficiency of vesicular traffic. In plants, disturbances in vesicular trafficking are well studied in quickly dividing root meristem cells or polar growing root hairs and pollen tubes. The development of the female gametophyte, a unique haploid reproductive structure located in the ovule, has received far less attention in studies of vesicular transport. Key molecules providing the specificity of vesicle formation and its subsequent recognition and fusion with the acceptor membrane are Rab proteins. Rabs are anchored to membranes by covalently linked geranylgeranyl group(s) that are added by the Rab geranylgeranyl transferase (RGT) enzyme. Here we show that Arabidopsis plants carrying mutations in the gene encoding the β-subunit of RGT (rgtb1) exhibit severely disrupted female gametogenesis and this effect is of sporophytic origin. Mutations in rgtb1 lead to internalization of the PIN1 and PIN3 proteins from the basal membranes to vesicles in provascular cells of the funiculus. Decreased transport of auxin out of the ovule is accompanied by auxin accumulation in tissue surrounding the growing gametophyte. In addition, female gametophyte development arrests at the uni- or binuclear stage in a significant portion of the rgtb1 ovules. These observations suggest that communication between the sporophyte and the developing female gametophyte relies on Rab-dependent vesicular traffic of the PIN1 and PIN3 transporters and auxin efflux out of the ovule.

中文翻译：

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依赖Rab的囊泡运输影响拟南芥中雌配子体发育

真核细胞依赖于囊泡运输的准确性和效率。在植物中，在快速分裂根分生组织细胞或极地生长的根毛和花粉管方面，对水泡运输的障碍进行了充分的研究。雌配子体的发育是位于胚珠中的独特的单倍体生殖结构，在水泡运输研究中受到的关注很少。提供小泡形成的特异性及其随后的识别和与受体膜融合的关键分子是Rab蛋白。Rab通过由Rab geranylgeranyl转移酶（RGT）酶添加的共价连接的geranylgeranyl基团锚定在膜上。在这里，我们显示拟南芥植物在RGT（rgtb1）的β亚基编码基因中携带突变）表现出严重破坏了女性配子发生的作用，这种作用是孢子起源的。rgtb1中的突变会导致PIN1和PIN3蛋白从基底膜到内膜的前血管中的囊泡内化。生长素从胚珠的运输减少伴随着生长素在生长中的配子体周围组织中的积累。此外，雌配子体发育停滞在rgtb1胚珠的很大一部分的单核或双核阶段。这些观察结果表明，孢子体与发育中的雌配子体之间的通讯依赖于PIN1和PIN3转运蛋白的Rab依赖性囊泡运输以及生长素从胚珠流出。