ERA（E.coli Ras-like protein）蛋白是一种在大肠杆菌中发现的特殊小G蛋白。该蛋白拥有两个高度保守的结构域，分别是结合和水解GTP的GTP酶结构域（GTPase）与结合RNA的KH结构域（K Homology domain）。前人研究发现，ERA在金鱼草中的同源蛋白ERG，其单插入突变体出现了未成熟种子死亡的现象。然而，其具体机制尚不清楚。拟南芥基因组含有两个ERG的同源蛋白，分别是定位于叶绿体中的AtERG1和定位于线粒体的AtERG2。这两个基因的功能也未见报道。 本研究首先证明，尽管AtERG2是一个核基因编码蛋白，但其通过其5’端的150个特异氨基酸序列定位于线粒体，并且能够结合线粒体小亚基组成成分18S mt-rRNA。另外，对PAtERG2：：GUS转基因拟南芥的GUS染色及利用qRT-PCR检测AtERG2转录水平等实验也表明，AtERG2在雌/雄胚子体及受精后合子早期的胚囊中特异高表达。对T-DNA单插入突变体aterg2-1 +/- 及aterg2-2 +/- 后代的基因组水平鉴定及表型观察发现，aterg2 +/- 突变体呈现纯合致死、角果长度缩短和部分种子早期发育抑制的现象。然而，其成熟种子萌发及营养生长并没有异常。进一步研究发现，aterg2-1 +/- 突变体雌雄配子体的发育并未受到明显的影响，但其胚胎被大量滞留在合子时期，而且部分种子发育到授粉后1.5天出现形态大小发育受到抑制，甚至2.0天出现塌陷萎缩的表型，最终导致杂合突变体近2/3种子败育。aterg2-1 +/- 突变体授粉后1.5天种子的曙红及ROS染色实验结果显示，突变体角果内近2/3的种子胚囊中出现了发育异常的线粒体云降解和活性氧的聚集；发育滞后的种子内响应ROS积累信号的一系列细胞凋亡通路蛋白和线粒体修复通路成员蛋白的转录水平出现了明显的升高。同时，我们对开花前的野生型拟南芥进行氯霉素处理直到开花后1.5天及2.0天，收集角果材料进行分子水平检测及表型观察。结果表明，氯霉素处理导致拟南芥角果变短，授粉后的合子发育停止，ROS积累以及相关基因转录水平上升。这些结果表明，氯霉素处理抑制蛋白合成后与aterg +/-突变的表型相似。 综上，根据实验结果可以认为AtERG2通过结合18S mt-rRNA，对线粒体核糖体的组装及ATPase S6等线粒体自身蛋白的合成起着重要作用。该基因突变后，影响了核糖体的组装，抑制线粒体自身蛋白的翻译，破坏线粒体呼吸链关键复合物的功能完整，从而造成胚囊内线粒体云的降解及活性氧的大量积累，进而引起细胞的死亡，最终结果就是引起大量拟南芥种子的早期败育及突变体纯合致死。因此，该基因对拟南芥种子的早期发育是必需的。

The ERA (E. coli RAS-like protein)-related GTPase (ERG) is a nuclear-encoded GTPase with two conserved domains: a GTPase domain and a K Homology domain. ERG plays a vital role in early seed development in Antirrhinum majus. However, the mechanism that regulates seed development remains unclear. Blasting the genome sequence revealed two homologies of ERG, AtERG1, and AtERG2 in Arabidopsis. In this study, we found that AtERG2 is localised in the mitochondria and binds mitochondrial 18S RNA. Promoter and transcript analyses indicated that AtERG2 was mainly expressed in the leaf vein, trichome, mature pollen, and ovule. The mutants of AtERG2 showed recessive lethal, gametophytic maternal effects, silique shortage, and early seed abortion, in which some seeds arrested in the zygotic stage at 1.5 days after pollination (DAP) and aborted at 2.0-DAP in aterg2-1 +/-. WE-CLSM stain showed plenty seeds got mitochondria cloud degradation in embryo sac during zygote embryo development stage. At the same time, reactive oxygen species (ROS) accumulated at 1.5-DAP in the arrested seeds, and the transcription of several ROS-responsible genes, WRKY40, ANAC017, and AOX1a, was up-regulated in the aterg2-1 +/- seeds which were arrested 1.5-and 2.0-DAP but not in wild-type (WT) and aterg2-1 +/- seeds. The cell death-related gene BAG6 was also transcriptionally activated in aterg2-1 +/- seeds arrested at 2.0-DAP. Chloramphenicol treatment during pollination induced a similar phenotype and gene expression pattern but showed no transcriptional changes of ANAC017 in WT. These results suggested that AtERG2 promotes early seed development by affecting the maturation of the mitochondria ribosome small subunit and mitochondrial protein translation in Arabidopsis.