Molecular Plant Biophysics and Biochemistry, Department of Biosciences, University of Salzburg, Salzburg, Austria.
Bioinformatics of Allergens, Department of Biosciences, University of Salzburg, Salzburg, Austria.
PLoS One. 2018 Aug 29;13(8):e0201480. doi: 10.1371/journal.pone.0201480. eCollection 2018.
The Characeae are multicellular green algae with very close relationship to land plants. Their internodal cells have been the subject of numerous (electro-)physiological studies. When exposed to light, internodal cells display alternating bands of low and high pH along their surface in order to facilitate carbon uptake required for photosynthesis. Here we investigated for the first time the subcellular membrane protein composition of acidic and alkaline regions in internodal cells of Chara australis R. Br. using MS-proteomics. The identified peptides were annotated to Chara unigenes using a custom-made Chara database generated from a transcriptome analysis and to orthologous Arabidopsis genes using TAIR (The Arabidopsis Information Resource) database. Apart from providing the first public-available, functionally-annotated sequence database for Chara australis, the proteome study, which is supported by immunodetection, identified several membrane proteins associated with acidic regions that contain a high density of specific plasma membrane (PM) invaginations, the charasomes, which locally increase the membrane area to overcome diffusion limitation in membrane transport. An increased abundance of PM H+ ATPases at charasomes is consistent with their role in the acidification of the environment, but the characean PM H+ ATPase sequence suggests a different regulation compared to higher plant PM H+ ATPases. A higher abundance of H+ co-transporters in the charasome-rich, acidic regions possibly reflects enhanced uptake of ions and nutrients. The increase in mitochondrial proteins confirms earlier findings about the accumulation of cortical mitochondria in the acidic zones. The significant enrichment of clathrin heavy chains and clathrin adaptor proteins as well as other proteins involved in trafficking indicate a higher activity of membrane transport in the charasome-rich than in charasome-poor areas. New and unexpected data, for instance the upregulation and abundance of vacuolar transporters correlating with the charasome-rich, acidic cell regions account for new perspectives in the formation of charasomes.
Characeae 是具有密切陆地植物关系的多细胞绿藻。它们的节间细胞一直是许多（电）生理学研究的主题。当暴露在光下时，节间细胞在其表面显示出交替的低 pH 和高 pH 带，以促进光合作用所需的碳吸收。在这里，我们首次使用 MS 蛋白质组学研究了 Chara australis R. Br. 节间细胞中酸性和碱性区域的亚细胞膜蛋白组成。使用从转录组分析生成的定制 Chara 数据库和 TAIR（拟南芥信息资源）数据库中的同源拟南芥基因，将鉴定的肽注释到 Chara 单基因。除了提供第一个公开可用的、功能注释的 Chara australis 序列数据库外，这项由免疫检测支持的蛋白质组研究鉴定了几种与富含酸性区域的膜蛋白相关的蛋白，这些蛋白含有高密度的特定质膜 (PM) 内陷，即 charasomes，它局部增加膜面积以克服膜转运中的扩散限制。charasomes 中 PM H+ATPase 的丰度增加与它们在环境酸化中的作用一致，但 characean PM H+ATPase 序列表明其与高等植物 PM H+ATPase 的调节不同。在富含 charasomes 的酸性区域中 H+共转运蛋白的丰度增加可能反映了离子和养分的摄取增强。线粒体蛋白的增加证实了以前关于皮质线粒体在酸性区积累的发现。网格蛋白重链和网格蛋白衔接蛋白以及其他参与运输的蛋白的显著富集表明，富含 charasomes 的区域比 charasome 较少的区域具有更高的膜转运活性。新的和意外的数据，例如与富含 charasomes 的酸性细胞区域相关的上调和丰度增加的液泡转运蛋白，为 charasomes 的形成提供了新的视角。
