Australian Research Council Centre of Excellence in Plant Energy Biology, M316, University of Western Australia, 35 Stirling Highway, Crawley WA 6009, Australia.
Plant J. 2011 Sep;67(6):1067-80. doi: 10.1111/j.1365-313X.2011.04658.x. Epub 2011 Jul 6.
We have identified a mitochondrial protein (RUG3) that is required for accumulation of mitochondrial respiratory chain complex I. RUG3 is related to human REGULATOR OF CHROMOSOME CONDENSATION 1 (RCC1) and Arabidopsis UV-B RESISTANCE 8 (UVR8). Although the family of RCC1-like proteins in Arabidopsis has over 20 members, UVR8 is the sole plant representative of this family to have been functionally characterized. Mitochondria from Arabidopsis plants lacking a functional RUG3 gene showed greatly reduced complex I abundance and activity. In contrast, accumulation of complexes III, IV and V of the oxidative phosphorylation system and the capacity for succinate-dependent respiration were unaffected. A comprehensive study of processes contributing to complex I biogenesis in rug3 mutants revealed that RUG3 is required for efficient splicing of the nad2 mRNA, which encodes a complex I subunit. A comparison of the formation of complex I assembly intermediates between rug3 and wild type mitochondria indicated that NAD2 enters the assembly pathway at an early stage. Remarkably, rug3 mutants displayed increased capacities for import of nucleus-encoded mitochondrial proteins into the organelle and showed moderately increased mitochondrial transcript levels. This observation is consistent with global transcript changes indicating enhanced mitochondrial biogenesis in the rug3 mutant in response to the complex I defect.
我们已经鉴定出一种线粒体蛋白（RUG3），它是线粒体呼吸链复合物 I 积累所必需的。RUG3 与人类染色质凝聚调节因子 1（RCC1）和拟南芥紫外线-B 抵抗 8（UVR8）有关。尽管拟南芥 RCC1 样蛋白家族有 20 多个成员，但 UVR8 是该家族中唯一具有功能特征的植物代表。缺乏功能性 RUG3 基因的拟南芥植物的线粒体显示出复合物 I 丰度和活性大大降低。相比之下，氧化磷酸化系统的复合物 III、IV 和 V 的积累和琥珀酸依赖性呼吸能力不受影响。对 rug3 突变体中参与复合物 I 生物发生的过程的全面研究表明，RUG3 是 nad2 mRNA 有效剪接所必需的，nad2 mRNA 编码复合物 I 亚基。对 rug3 和野生型线粒体中复合物 I 组装中间体形成的比较表明，NAD2 在早期进入组装途径。值得注意的是，rug3 突变体表现出导入核编码线粒体蛋白进入细胞器的能力增加，并且线粒体转录本水平适度增加。这一观察结果与表明 rug3 突变体中增强的线粒体生物发生以响应复合物 I 缺陷的全局转录变化一致。
