Satjarak Anchittha, Graham Linda E
Department of Botany, University of Wisconsin-Madison, 430 Lincoln Drive, Madison, Wisconsin, USA.
J Phycol. 2017 Apr;53(2):415-424. doi: 10.1111/jpy.12515. Epub 2017 Mar 6.
Prasinophytes form a paraphyletic assemblage of early diverging green algae, which have the potential to reveal the traits of the last common ancestor of the main two green lineages: (i) chlorophyte algae and (ii) streptophyte algae. Understanding the genetic composition of prasinophyte algae is fundamental to understanding the diversification and evolutionary processes that may have occurred in both green lineages. In this study, we sequenced the chloroplast genome of Pyramimonas parkeae NIES254 and compared it with that of P. parkeae CCMP726, the only other fully sequenced P. parkeae chloroplast genome. The results revealed that P. parkeae chloroplast genomes are surprisingly variable. The chloroplast genome of NIES254 was larger than that of CCMP726 by 3,204 bp, the NIES254 large single copy was 288 bp longer, the small single copy was 5,088 bp longer, and the IR was 1,086 bp shorter than that of CCMP726. Similarity values of the two strains were almost zero in four large hot spot regions. Finally, the strains differed in copy number for three protein-coding genes: ycf20, psaC, and ndhE. Phylogenetic analyses using 16S and 18S rDNA and rbcL sequences resolved a clade consisting of these two P. parkeae strains and a clade consisting of these plus other Pyramimonas isolates. These results are consistent with past studies indicating that prasinophyte chloroplast genomes display a higher level of variation than is commonly found among land plants. Consequently, prasinophyte chloroplast genomes may be less useful for inferring the early history of Viridiplantae than has been the case for land plant diversification.
绿藻门绿藻纲绿藻目绿藻科绿藻属藻类形成了一个早期分化的绿藻的并系类群，它们有可能揭示主要两个绿藻谱系的最后共同祖先的特征：（i）绿藻纲藻类和（ii）链形植物藻类。了解绿藻门绿藻纲绿藻目绿藻科绿藻属藻类的遗传组成对于理解这两个绿藻谱系中可能发生的多样化和进化过程至关重要。在本研究中，我们对帕克氏扁藻NIES254的叶绿体基因组进行了测序，并将其与帕克氏扁藻CCMP726的叶绿体基因组进行了比较，后者是唯一另一个已完全测序的帕克氏扁藻叶绿体基因组。结果表明，帕克氏扁藻的叶绿体基因组差异惊人。NIES254的叶绿体基因组比CCMP726的大3204 bp，NIES254的大单拷贝长288 bp，小单拷贝长5088 bp，反向重复序列比CCMP726短1086 bp。在四个大的热点区域，这两个菌株的相似性值几乎为零。最后，这两个菌株在三个蛋白质编码基因（ycf20、psaC和ndhE）的拷贝数上存在差异。使用16S和18S rDNA以及rbcL序列进行的系统发育分析解析出一个由这两个帕克氏扁藻菌株组成的分支和一个由这些菌株加上其他扁藻分离株组成的分支。这些结果与过去的研究一致，表明绿藻门绿藻纲绿藻目绿藻科绿藻属藻类的叶绿体基因组显示出比陆地植物中常见的更高水平的变异。因此，与陆地植物多样化的情况相比，绿藻门绿藻纲绿藻目绿藻科绿藻属藻类的叶绿体基因组在推断绿藻植物早期历史方面可能用处较小。
