梅花草属叶绿体基因组进化分析

叶绿体基因组序列变异和基因组成等特征可有效反映植物类群间的系统发育和进化关系。本研究利用Illumina高通量测序平台对梅花草属（Parnassia）及其近缘属5种植物的叶绿体基因组进行测序和组装，同时基于已发表的近缘种叶绿体基因组信息，对梅花草属叶绿体基因组结构特征、序列遗传变异和蛋白编码基因密码子偏好性比对分析。结果显示：梅花草属叶绿体基因组整体结构较为保守，均为四分体结构；梅花草多个基因出现假基因化，而本属其他物种叶绿体基因组成一致，均编码115个基因；与近缘属物种相比，本属所有物种均丢失rpl16基因的内含子；蛋白质编码基因的非同义/同义替代率比值较低，叶绿体基因可能经历纯化选择作用；密码子偏好性聚类结果与蛋白编码序列重建的系统发育关系结果一致。本研究表明选择压力可能在梅花草属叶绿体基因组蛋白编码基因进化过程中发挥作用，有助于进一步理解梅花草属植物的进化和适应机制。

Evolutionary Analysis of Chloroplast Genome of Parnassia

Sequence variation and gene composition of chloroplast genome could effectively reflect the phylogenetic and evolutionary relationships among plants. In this study， DNA libraries were prepared and sequenced by the Illumina HiSeq， chloroplast genomes offive species of Parnassia and allied genera were assembled respectively， and the structural characteristics， sequence genetic variation and codon preference of protein coding genes of Parnassia chloroplast genome with related species were compared and analyzed. The results showed that the chloroplast genome of Parnassia was conserved tetrad structure， and pseudogenization of several genes were found in P. palustris， but the chloroplast gene composition of other species was the same， encoding 115 genes. Compared with the relative species， the intron of rpl16 gene were lost in all species of Parnassia. The ratio of nonsynonymous/synonymous substitution rate of protein coding genes was low， and chloroplast genes might experience purification selection. Codon preference was consistent with the phylogenetic relationship shown by protein coding sequences. This study reveals that selection pressure may play an important role in the evolution of protein-coding genes in the chloroplast genome of Parnassia， which could enhance the understanding about evolution and adaptation of this genus.