Comparative molecular evolution of newly discovered picocyanobacterial strains reveals a phylogenetically informative variable region of β-phycoerythrin
Comparative molecular evolution of newly discovered picocyanobacterial strains reveals a phylogenetically informative variable region of β-phycoerythrin
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DOI：
10.1111/j.1529-8817.2006.00282.x
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发表时间：
2006-12-01
影响因子：
2.9
通讯作者：
Wood, A. Michelle
中科院分区：
文献类型：
--
作者：
Everroad, R. Craig;Wood, A. Michelle
利用16 S rDNA、RNA聚合酶rpoC 1和藻红蛋白（PE）基因座的两个元件cpeA和cpeB（编码PE的α和β亚基）的部分序列，对来自阿拉伯海的10株微蓝细菌的遗传多样性和系统发育位置进行了研究。9个菌株表现出几乎相同的光谱表型的基础上，在体内激发光谱PE荧光发射，似乎是菌株合成藻胆素（PUB）缺乏PE。这些菌株包括一个，聚球藻属G2.1，已经知道是密切相关的丝状蓝藻，而不是通常研究的5.1亚群的海洋聚球藻。第10菌株是一种缺乏PE的菌株，这是令人感兴趣的，因为它是从具有这种表型的微蓝细菌相对罕见的开放海洋条件下分离出来的。串联的16 S rDNA和rpoC 1数据集的系统发育分析表明，没有以前描述的菌株是海洋聚球藻的5.1亚群的成员，也没有密切相关的菌株G2.1。相反，它们形成了一个得到充分支持的，以前未描述的蓝藻分支，是蓝藻的姐妹。因此，这些菌株代表了来自海洋沃茨的第一个含PE的蓝藻，并且它们定义的谱系包括来自相同环境的具有PE缺乏表型的菌株。PE序列数据的分析表明，PE脱辅基蛋白在G2.1谱系和由研究菌株代表的Cyanobium样谱系中独立进化。它还揭示了一个高变区的β-亚基之前没有描述过，在这个区域的变化显示了一个模式之间的广泛的含PE的生物体一致的系统发育关系推断从其他基因。这表明，PUB缺乏光谱表型更有可能已经在远亲系统发育谱系中通过发散或收敛进化而不是通过横向基因转移进化。保守的PE基因序列和推测的高变区的氨基酸序列在原绿球藻PE、红藻PE、来自海洋聚球藻5.1亚群的含PUB的PE、来自蓝藻样菌株的PE和来自其他蓝藻（包括菌株G2.1）的PE之间显示出相当大的分歧。因此，PE基因的高变区似乎可以用作分类群特异性标记。
The genetic diversity and phylogenetic position of 10 strains of picocyanobacteria from the Arabian Sea were examined using partial sequences from three loci: 16S rDNA, RNA polymerase rpoC1, and two elements of the phycoerythrin (PE) locus, cpeA and cpeB which encode for the alpha and beta subunit of PE. Nine of the strains showed nearly identical spectral phenotypes based on the in vivo excitation spectrum for PE fluorescence emission and appear to be strains synthesizing a phycourobilin (PUB)-lacking PE. These strains include one, Synechococcus sp. G2.1, already known to be closely related to filamentous cyanobacteria and not to the commonly studied 5.1 subcluster of marine Synechococcus. The 10th strain was a PE-lacking strain that was of interest because it was isolated from open-ocean conditions where picocyanobacteria with this phenotype are relatively uncommon. Phylogenetic analysis of the concatenated 16S rDNA and rpoC1 data sets showed that none of the previously described strains were members of the 5.1 subcluster of marine Synechococcus, nor were they closely related to strain G2.1. Instead, they form a well-supported and previously undescribed clade of cyanobacteria that is sister to Cyanobium. Thus, these strains represent the first PE-containing Cyanobium from oceanic waters, and the lineage they define includes a strain with a PE-lacking phenotype from the same environment. Analysis of the PE sequence data showed the PE apoprotein has evolved independently in the G2.1 lineage and the Cyanobium-like lineage represented by the study strains. It also revealed a hypervariable region of the beta-subunit not described previously; variation in this region shows a pattern among a wide range of PE-containing organisms congruent with the phylogenetic relationships inferred from other genes. This suggests that the PUB-lacking spectral phenotype is more likely to have evolved in distantly related phylogenetic lineages by either divergent or convergent evolution than by lateral gene transfer. Both the conserved PE gene sequences and the inferred amino acid sequences for the hypervariable region show considerable divergence among Prochlorococcus PEs, red algal PEs, PUB-containing PEs from the marine Synechococcus 5.1 subcluster, PEs from the Cyanobium-like strains, and PEs from other cyanobacteria (including strain G2.1). Thus, it appears that the hypervariable region of the PE gene can be used as a taxon-specific marker.