硅藻是海洋与淡水中的一种微型藻类，在海洋中居支配地位，占地球上初级生产力的约1/5。本期Nature发布了三角褐指藻（Phaeodactylum tricornutum）的完整基因组序列，它是第二个被测序的硅藻。与第一个被测序的硅藻——假微型海链藻（Thalassiosira pseudonana）所做的对比表明，通过硅藻与细菌之间的双向基因转移，硅藻从细菌获得了数百个基因。基因转移在硅藻演化中似乎是普遍存在的，产生了基因的非正规组合（其中包括一些来自植物和动物的基因），很可能在营养管理和环境信号作用中起重要作用。（生物谷Bioon.com）
生物谷推荐原始出处：
Nature 456, 239-244 (13 November 2008) | doi:10.1038/nature07410
The Phaeodactylum genome reveals the evolutionary history of diatom genomes
Diatoms are photosynthetic secondary endosymbionts found throughout marine and freshwater environments, and are believed to be responsible for around one-fifth of the primary productivity on Earth1, 2. The genome sequence of the marine centric diatom Thalassiosira pseudonana was recently reported, revealing a wealth of information about diatom biology3, 4, 5. Here we report the complete genome sequence of the pennate diatom Phaeodactylum tricornutum and compare it with that of T. pseudonana to clarify evolutionary origins, functional significance and ubiquity of these features throughout diatoms. In spite of the fact that the pennate and centric lineages have only been diverging for 90 million years, their genome structures are dramatically different and a substantial fraction of genes (40%) are not shared by these representatives of the two lineages. Analysis of molecular divergence compared with yeasts and metazoans reveals rapid rates of gene diversification in diatoms. Contributing factors include selective gene family expansions, differential losses and gains of genes and introns, and differential mobilization of transposable elements. Most significantly, we document the presence of hundreds of genes from bacteria. More than 300 of these gene transfers are found in both diatoms, attesting to their ancient origins, and many are likely to provide novel possibilities for metabolite management and for perception of environmental signals. These findings go a long way towards explaining the incredible diversity and success of the diatoms in contemporary oceans.
