Radin Ivan, Mansilla Natanael, Rödel Gerhard, Steinebrunner Iris
Institute for Genetics, Department of Biology, Technische Universität Dresden Dresden, Germany.
Instituto de Agrobiotecnología del Litoral-Consejo Nacional de Investigaciones Científicas y Técnicas, Universidad Nacional del Litoral Santa Fe, Argentina.
Front Plant Sci. 2015 Dec 18;6:1091. doi: 10.3389/fpls.2015.01091. eCollection 2015.
Members of the ubiquitous COX11 (cytochrome c oxidase 11) protein family are involved in copper delivery to the COX complex. In this work, we characterize the Arabidopsis thaliana COX11 homolog (encoded by locus At1g02410). Western blot analyses and confocal microscopy identified Arabidopsis COX11 as an integral mitochondrial protein. Despite sharing high sequence and structural similarities, the Arabidopsis COX11 is not able to functionally replace the Saccharomyces cerevisiae COX11 homolog. Nevertheless, further analysis confirmed the hypothesis that Arabidopsis COX11 is essential for COX activity. Disturbance of COX11 expression through knockdown (KD) or overexpression (OE) affected COX activity. In KD lines, the activity was reduced by 50%, resulting in root growth inhibition, smaller rosettes and leaf curling. In OE lines, the reduction was less pronounced (80% of the wild type), still resulting in root growth inhibition. Additionally, pollen germination was impaired in COX11 KD and OE plants. This effect on pollen germination can only partially be attributed to COX deficiency and may indicate a possible auxiliary role of COX11 in ROS metabolism. In agreement with its role in energy production, the COX11 promoter is highly active in cells and tissues with high-energy demand for example shoot and root meristems, or vascular tissues of source and sink organs. In COX11 KD lines, the expression of the plasma-membrane copper transporter COPT2 and of several copper chaperones was altered, indicative of a retrograde signaling pathway pertinent to copper homeostasis. Based on our data, we postulate that COX11 is a mitochondrial chaperone, which plays an important role for plant growth and pollen germination as an essential COX complex assembly factor.
普遍存在的COX11（细胞色素c氧化酶11）蛋白家族成员参与向COX复合体输送铜。在本研究中，我们对拟南芥COX11同源物（由基因座At1g02410编码）进行了表征。蛋白质免疫印迹分析和共聚焦显微镜鉴定出拟南芥COX11是一种线粒体内膜蛋白。尽管拟南芥COX11与酿酒酵母COX11同源物具有高度的序列和结构相似性，但它不能在功能上替代酿酒酵母的COX11同源物。然而，进一步分析证实了拟南芥COX11对COX活性至关重要这一假设。通过敲低（KD）或过表达（OE）干扰COX11的表达会影响COX活性。在KD系中，活性降低了约50%，导致根生长受抑制、莲座叶变小和叶片卷曲。在OE系中，活性降低不太明显（约为野生型的80%），但仍导致根生长受抑制。此外，COX11 KD和OE植株的花粉萌发也受到损害。这种对花粉萌发的影响只能部分归因于COX缺乏，可能表明COX11在活性氧代谢中具有可能的辅助作用。与其在能量产生中的作用一致，COX11启动子在对能量需求高的细胞和组织中高度活跃，例如茎尖和根尖分生组织，或源库器官的维管组织。在COX11 KD系中，质膜铜转运蛋白COPT2和几种铜伴侣蛋白的表达发生了改变，表明存在与铜稳态相关的逆行信号通路。基于我们的数据，我们推测COX11是一种线粒体伴侣蛋白，作为COX复合体组装的必需因子，对植物生长和花粉萌发起着重要作用。
