VPS9a, the common activator for two distinct types of Rab5 GTPases, is essential for the development of Arabidopsis thaliana
VPS9a, the common activator for two distinct types of Rab5 GTPases, is essential for the development of Arabidopsis thaliana
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DOI：
10.1105/tpc.107.053876
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发表时间：
2007-11-01
期刊：
影响因子：
11.6
通讯作者：
Nakano, Akihiko
中科院分区：
文献类型：
--
作者：
Goh, Tatsuaki;Uchida, Wakana;Nakano, Akihiko
Rab5 是 Rab GTPases 的一个亚家族，作为分子开关调节多种内体功能。拟南芥有两种不同类型的 Rab5 成员 GTP 酶：常规类型 ARA7 和 RHA1，以及植物特异性类型 ARA6。我们发现，尽管结构不同，但只有一种名为 VPS9a 的鸟嘌呤核苷酸交换因子 (GEF) 可以在体外将所有 Rab5 成员激活为 GTP 结合形式。在vps9a-1突变体中，其GEF活性完全丧失，胚胎发生在鱼雷阶段被阻止。绿色荧光蛋白 (GFP)-ARA7 和 ARA6-GFP 扩散在 vps9a-1 中 GDP 固定的 Rab5 突变体的胞质中，表明两种类型的 GTPase 均受 VPS9a 调节。在漏水vps9a-2突变体中，初生根的伸长受到严重影响。 ARA7 的 GTP 固定形式的过表达抑制了 vps9a-2 突变，但 ARA6 的过表达没有明显的影响。这些结果表明，两种类型的植物 Rab5 成员在功能上存在差异，尽管它们受到相同的激活剂 VPS9a 的调节。
Rab5, a subfamily of Rab GTPases, regulates a variety of endosomal functions as a molecular switch. Arabidopsis thaliana has two different types of Rab5-member GTPases: conventional type, ARA7 and RHA1, and a plant-specific type, ARA6. We found that only one guanine nucleotide exchange factor (GEF), named VPS9a, can activate all Rab5 members to GTP-bound forms in vitro in spite of their diverged structures. In the vps9a-1 mutant, whose GEF activity is completely lost, embryogenesis was arrested at the torpedo stage. Green fluorescent protein (GFP)-ARA7 and ARA6-GFP were diffused in cytosol like GDP-fixed mutants of Rab5 in vps9a-1, indicating that both types of GTPase are regulated by VPS9a. In the leaky vps9a-2 mutant, elongation of the primary root was severely affected. Overexpression of the GTP-fixed form of ARA7 suppressed the vps9a-2 mutation, but overexpression of ARA6 had no apparent effects. These results indicate that the two types of plant Rab5 members are functionally differentiated, even though they are regulated by the same activator, VPS9a.