Background

The sequences of several important mitochondrion-encoded genes involved in respiration in higher plants are interrupted by introns. Many nuclear-encoded factors are involved in splicing these introns, but the mechanisms underlying this splicing remain unknown.

Results

We isolated and characterized a rice mutant named floury shrunken endosperm 5 (fse5). In addition to having floury shrunken endosperm, the fse5 seeds either failed to germinate or produced seedlings which grew slowly and died ultimately. Fse5 encodes a putative plant organelle RNA recognition (PORR) protein targeted to mitochondria. Mutation of Fse5 hindered the splicing of the first intron of nad4, which encodes an essential subunit of mitochondrial NADH dehydrogenase complex I. The assembly and NADH dehydrogenase activity of complex I were subsequently disrupted by this mutation, and the structure of the mitochondria was abnormal in the fse5 mutant. The FSE5 protein was shown to interact with mitochondrial intron splicing factor 68 (MISF68), which is also a splicing factor for nad4 intron 1 identified previously via yeast two-hybrid (Y2H) assays.

Conclusion

Fse5 which encodes a PORR domain-containing protein, is essential for the splicing of nad4 intron 1, and loss of Fse5 function affects seed development and seedling growth.

中文翻译：

---

Rice FLOURY SHRUNKEN ENDOSPERM 5编码线粒体nad4内含子1的顺式剪接所需的推定的植物细胞器RNA识别蛋白。

背景

涉及高等植物呼吸作用的几个重要的线粒体编码基因的序列被内含子打断。这些内含子的剪接涉及许多核编码因子，但这种剪接的机制尚不清楚。

结果

我们分离并鉴定了一个水稻突变体，名为面粉皱缩的胚乳5（fse5）。fse5种子除了具有皱缩的胚乳外，还不能发芽或无法长出并最终死亡的幼苗。Fse5编码针对线粒体的假定植物细胞器RNA识别（PORR）蛋白。Fse5的突变阻碍了nad4的第一个内含子的剪接，后者编码线粒体NADH脱氢酶复合物I的必需亚基。复合物I的组装和NADH脱氢酶活性随后被该突变破坏，并且线粒体的结构异常。该fse5突变体。FSE5蛋白显示与线粒体内含子剪接因子68（MISF68）相互作用，它也是先前通过酵母双杂交（Y2H）分析鉴定的nad4内含子1的剪接因子。

结论

Fse5其编码含有PORR域的蛋白质，是用于拼接必不可少nad4内含子1，并丧失Fse5函数影响种子发育和幼苗生长。