Vancaester Emmelien, Depuydt Thomas, Osuna-Cruz Cristina Maria, Vandepoele Klaas
Department of Plant Biotechnology and Bioinformatics, Ghent University, Ghent, Belgium.
VIB Center for Plant Systems Biology, Ghent, Belgium.
Mol Biol Evol. 2020 Nov 1;37(11):3243-3257. doi: 10.1093/molbev/msaa182.
Diatoms are a diverse group of mainly photosynthetic algae, responsible for 20% of worldwide oxygen production, which can rapidly respond to favorable conditions and often outcompete other phytoplankton. We investigated the contribution of horizontal gene transfer (HGT) to its ecological success. A large-scale phylogeny-based prokaryotic HGT detection procedure across nine sequenced diatoms showed that 3-5% of their proteome has a horizontal origin and a large influx occurred at the ancestor of diatoms. More than 90% of HGT genes are expressed, and species-specific HGT genes in Phaeodactylum tricornutum undergo strong purifying selection. Genes derived from HGT are implicated in several processes including environmental sensing and expand the metabolic toolbox. Cobalamin (vitamin B12) is an essential cofactor for roughly half of the diatoms and is only produced by bacteria. Five consecutive genes involved in the final synthesis of the cobalamin biosynthetic pathway, which could function as scavenging and repair genes, were detected as HGT. The full suite of these genes was detected in the cold-adapted diatom Fragilariopsis cylindrus. This might give diatoms originating from the Southern Ocean, a region typically depleted in cobalamin, a competitive advantage. Overall, we show that HGT is a prevalent mechanism that is actively used in diatoms to expand its adaptive capabilities.
硅藻是一类多样的主要进行光合作用的藻类，贡献了全球20%的氧气产量，它们能够迅速对有利条件做出反应，并且常常胜过其他浮游植物。我们研究了水平基因转移（HGT）对其生态成功的贡献。一项基于系统发育的针对9种已测序硅藻的大规模原核生物HGT检测程序表明，它们蛋白质组的3% - 5%有水平起源，并且在硅藻的祖先时期发生了大量基因流入。超过90%的HGT基因是表达的，三角褐指藻中物种特异性的HGT基因经历了强烈的纯化选择。源自HGT的基因涉及包括环境感知在内的多个过程，并扩展了代谢工具箱。钴胺素（维生素B12）是大约一半硅藻必需的辅因子，且仅由细菌产生。参与钴胺素生物合成途径最终合成的五个连续基因被检测为HGT，它们可能起到清除和修复基因的作用。在适应寒冷的圆柱脆杆藻中检测到了这整套基因。这可能赋予源自南大洋（一个通常缺乏钴胺素的区域）的硅藻竞争优势。总体而言，我们表明HGT是一种普遍存在的机制，硅藻积极利用它来扩展其适应能力。
