Accelerated evolution associated with genome reduction in a free-living prokaryote.
Accelerated evolution associated with genome reduction in a free-living prokaryote.
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DOI：
10.1186/gb-2005-6-2-r14
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发表时间：
2005
期刊：
影响因子：
12.3
通讯作者：
Partensky F
中科院分区：
文献类型：
--
作者：
Dufresne A;Garczarek L;Partensky F
原绿球藻属。是基因组非常小的海洋细菌。然而，这些基因组减少的进化机制似乎与细胞内细菌基因组尺寸减小的机制不同。原绿球藻（海洋中最小且最丰富的光合生物）的三个完整基因组最近已发表。比较基因组分析表明，该属内发生了基因组收缩，与 G+C 含量急剧减少有关。由于迄今为止描述的所有基因组减少的例子都仅限于内共生体或病原体，具有依赖于宿主的生活方式，在原绿球藻中观察到的基因组减少是第一个记录在案的自由生活生物体中这种过程的例子。我们的结果清楚地表明，P. marinus SS120 中基因组的减少伴随着蛋白质进化速率的增加，这在 P. marinus MED4 中更为明显。这种加速影响了蛋白质编码基因的每个功能类别。相比之下，该属的 16S rRNA 基因似乎是按照时钟方式进化的。我们观察到 MED4 和 SS120 丢失了几个 DNA 修复基因，这些基因的缺失可能与突变偏差和氨基酸取代的加速有关。我们已经研究了该过程中涉及的进化机制，该机制与已知的依赖于宿主的生物体的进化机制不同。事实上，原绿球藻中发生的大多数取代必须是选择性中性的，因为种群规模大，遗传漂移低，纯化选择强。我们假设原绿球藻辐射内基因组减少的主要驱动力是有利于该生物体适应其环境的选择性过程。为该属的基因组进化提出了一个设想。
Prochlorococcus sp. are marine bacteria with very small genomes. The mechanisms by which these reduced genomes have evolved appears, however, to be distinct from those that have led to small genome size in intracellular bacteria. Three complete genomes of Prochlorococcus species, the smallest and most abundant photosynthetic organism in the ocean, have recently been published. Comparative genome analyses reveal that genome shrinkage has occurred within this genus, associated with a sharp reduction in G+C content. As all examples of genome reduction characterized so far have been restricted to endosymbionts or pathogens, with a host-dependent lifestyle, the observed genome reduction in Prochlorococcus is the first documented example of such a process in a free-living organism. Our results clearly indicate that genome reduction has been accompanied by an increased rate of protein evolution in P. marinus SS120 that is even more pronounced in P. marinus MED4. This acceleration has affected every functional category of protein-coding genes. In contrast, the 16S rRNA gene seems to have evolved clock-like in this genus. We observed that MED4 and SS120 have lost several DNA-repair genes, the absence of which could be related to the mutational bias and the acceleration of amino-acid substitution. We have examined the evolutionary mechanisms involved in this process, which are different from those known from host-dependent organisms. Indeed, most substitutions that have occurred in Prochlorococcus have to be selectively neutral, as the large size of populations imposes low genetic drift and strong purifying selection. We assume that the major driving force behind genome reduction within the Prochlorococcus radiation has been a selective process favoring the adaptation of this organism to its environment. A scenario is proposed for genome evolution in this genus.
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影响因子：
4.4
作者：
Fuller, NJ;Marie, D;Scanlan, DJ
通讯作者：
Scanlan, DJ
影响因子：
3.9
作者：
Andersson, SGE;Sharp, PM
通讯作者：
Sharp, PM
影响因子：
4.5
作者：
Moore, LR;Chisholm, SW
通讯作者：
Chisholm, SW
DOI：
10.1073/pnas.93.7.2873
发表时间：
1996-04-02
影响因子：
11.1
作者：
Moran, NA
通讯作者：
Moran, NA
影响因子：
30.8
作者：
Akman, L;Yamashita, A;Aksoy, S
通讯作者：
Aksoy, S