Dong Chun-Juan, Wu Ai-Min, Du Shao-Jun, Tang Kai, Wang Yun, Liu Jin-Yuan
Laboratory of Plant Molecular Biology, Center for Plant Biology, School of Life Sciences, Tsinghua University, Beijing, China.
PLoS One. 2016 Sep 15;11(9):e0162928. doi: 10.1371/journal.pone.0162928. eCollection 2016.
GRIM-19 (Gene associated with Retinoid-Interferon-induced Mortality 19) is a subunit of mitochondrial respiratory complex I in mammalian systems, and it has been demonstrated to be a multifunctional protein involved in the cell cycle, cell motility and innate immunity. However, little is known about the molecular functions of its homologues in plants. Here, we characterised GhMCS1, an orthologue of human GRIM-19 from cotton (Gossypium hirsutum L.), and found that it was essential for maintaining complex integrity and mitochondrial function in cotton. GhMCS1 was detected in various cotton tissues, with high levels expressed in developing fibres and flowers and lower levels in leaves, roots and ovules. In fibres at different developmental stages, GhMCS1 expression peaked at 5-15 days post anthesis (dpa) and then decreased at 20 dpa and diminished at 25 dpa. By Western blot analysis, GhMCS1 was observed to be localised to the mitochondria of cotton leaves and to colocalise with complex I. In Arabidopsis, GhMCS1 overexpression enhanced the assembly of complex I and thus respiratory activity, whereas the GhMCS1 homologue (At1g04630) knockdown mutants showed significantly decreased respiratory activities. Furthermore, the mutants presented with some phenotypic changes, such as smaller whole-plant architecture, poorly developed seeds and fewer trichomes. More importantly, in the cotton fibres, both the GhMCS1 transcript and protein levels were correlated with respiratory activity and fibre developmental phase. Our results suggest that GhMCS1, a functional ortholog of the human GRIM-19, is an essential subunit of mitochondrial complex I and is involved in cotton fibre development. The present data may deepen our knowledge on the potential roles of mitochondria in fibre morphogenesis.
GRIM-19（类视黄醇-干扰素诱导死亡率相关基因19）是哺乳动物系统中线粒体呼吸复合体I的一个亚基，并且已被证明是一种参与细胞周期、细胞运动和先天免疫的多功能蛋白质。然而，对于其在植物中的同源物的分子功能却知之甚少。在此，我们对棉花（陆地棉）中人类GRIM-19的直系同源物GhMCS1进行了表征，发现它对于维持棉花中线粒体复合体的完整性和线粒体功能至关重要。在棉花的各种组织中都检测到了GhMCS1，在发育中的纤维和花中高水平表达，而在叶、根和胚珠中表达水平较低。在不同发育阶段的纤维中，GhMCS1的表达在开花后5 - 15天达到峰值，然后在20天开花后下降，并在25天开花后消失。通过蛋白质免疫印迹分析，观察到GhMCS1定位于棉花叶片的线粒体中，并与复合体I共定位。在拟南芥中，GhMCS1的过表达增强了复合体I的组装，从而增强了呼吸活性，而GhMCS1同源物（At1g04630）的敲除突变体显示呼吸活性显著降低。此外，这些突变体出现了一些表型变化，如整株植物结构较小、种子发育不良和毛状体较少。更重要的是，在棉花纤维中，GhMCS1的转录本和蛋白质水平都与呼吸活性和纤维发育阶段相关。我们的结果表明，GhMCS1作为人类GRIM-19的功能直系同源物，是线粒体复合体I的一个必需亚基，并参与棉花纤维发育。目前的数据可能会加深我们对线粒体在纤维形态发生中潜在作用的认识。
