OsRab5a regulates endomembrane organization and storage protein trafficking in rice endosperm cells
OsRab5a regulates endomembrane organization and storage protein trafficking in rice endosperm cells
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OsRab5a 调节水稻胚乳细胞内膜组织和储存蛋白运输
DOI：
10.1111/j.1365-313x.2010.04370.x
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发表时间：
2010-12-01
期刊：
影响因子：
7.2
通讯作者：
Wan, Jianmin
中科院分区：
文献类型：
--
作者：
Wang, Yihua;Ren, Yulong;Wan, Jianmin
水稻谷蛋白是在内质网（ER）合成的前体（前谷蛋白），并被运输到蛋白质储存液泡，在那里它们被加工成成熟蛋白。该过程的分子基础在很大程度上尚不清楚。在这里，我们报告的分离的水稻突变体，gpa1，积累57 kDa的谷蛋白原在种子和胚乳有面粉外观。透射电子显微镜分析表明，gpa1胚乳细胞有一个扩大的ER腔和一个较小的蛋白体II（PBII），并积累了三种类型的新产生的亚细胞结构。此外，gpa1胚乳细胞中的一部分谷蛋白没有被传递到PBII，而是被错误地靶向到两个新产生的结构或分泌。发现对应于gpa1突变的基因是OsRab5a，其编码小的GT3。在拟南芥原生质体中，OsRab5a蛋白被发现主要与AtVSR 2共定位，AtVSR 2是前液泡室（PVC）的分子标记。我们得出结论，OsRab5a在运输的存储蛋白PBII中起着至关重要的作用，可能是其功能的一部分，在组织内膜系统发育的水稻胚乳细胞。
P>Rice glutelins are synthesized at the endoplasmic reticulum (ER) as precursors (pro-glutelins), and are transported to protein storage vacuoles, where they are processed into mature proteins. The molecular basis of this process is largely unknown. Here, we report the isolation of a rice mutant, gpa1, that accumulates 57 kDa pro-glutelins in seeds and whose endosperm has a floury appearance. Transmission electron microscopy analysis showed that the gpa1 endosperm cells have an enlarged ER lumen and a smaller protein body II (PBII), and accumulated three types of newly generated subcellular structures. Moreover, a proportion of glutelins in the gpa1 endosperm cells were not delivered to PBII, and instead were mis-targeted to two of the newly generated structures or secreted. The gene corresponding to the gpa1 mutation was found to be OsRab5a, which encodes a small GTPase. In Arabidopsis protoplasts, OsRab5a protein was found to co-localize predominantly with AtVSR2, a molecular marker for the pre-vacuolar compartments (PVC). We conclude that OsRab5a plays an essential role in trafficking of storage protein to PBII, possibly as part of its function in organizing the endomembrane system in developing endosperm cells of rice.