乳苣叶绿体基因组特征及其系统发育分析

乳苣（Mulgedium tataricum）为菊科（Compositae）乳苣属（Mulgedium）植物，该物种含有天然黄酮类化合物，具有清热解毒、抗肿瘤、抗氧化等作用。叶绿体基因组中含有大量功能基因，在物种鉴定及系统发育中具有重要作用。采用高通量测序技术获得乳苣全长叶绿体基因组序列，并与NCBI已公布的32个菊科物种及拟南芥（Arabidopsis thaliana）的叶绿体基因组进行了系统发育分析。结果显示，乳苣叶绿体基因组大小为152 401 bp，呈现出典型的环状四分体结构，其包含有一对反向重复序列区（IRa和IRb）、大单拷贝区（LSC）和小单拷贝区（SSC），它们的长度分别为25 010、83 833和18 548 bp。共注释得到132个基因，其中包含8个rRNA基因、37个tRNA基因和87个mRNA基因；SSR位点分析发现,基因组序列中含有21个散在重复序列和197个串联重复序列。边界分析表明，乳苣与其他5个菊苣族物种在边界基因上存在一定差异，且6个菊苣族物种在IR/SC区出现明显扩张和收缩。系统进化分析将菊科14个属的33个物种被聚为两个分支：第一分支包括乳苣属（Mulgedium）、莴苣属(Lactuca)、蒲公英属(Taraxacum)、苦苣菜属(Sonchus)、香青属(Anaphalis)、火绒草属(Leontopodium)、茼蒿属(Chrysanthemum)、蒿属(Artemisia)、紫菀属(Aster)和向日葵属(Helianthus)，其中乳苣属和莴苣属的亲缘关系最近；第二分支包括蓟属（Cirsium）、红花属（Carthamus）、风毛菊属（Saussurea）和苍术属（Atractylodes）。研究结果为乳苣属植物的物种鉴定、系统进化及资源开发利用等奠定新的证据和材料基础。

Chloroplast Genome Structure Characteristic and Phylogenetic Analysis of Mulgedium tataricum

Mulgedium tataricumis a Compositae, Mulgedium plant, which contains natural flavonoids, including heat-clearing and detoxification, anti-tumor, and anti-oxidant, etc. Chloroplast genome contains a large number of functional genes, which play important roles in species identification and phylogeny. In this study, the chloroplast genome DNA was sequenced using high-throughput sequencing technology to obtain the full-length chloroplast genome sequence, and the chloroplast genome was assembled, annotated and characterized. Phylogenetic analysis of chloroplast genomes from 32 Compositae species and Arabidopsis thaliana was performed. The results showed that the whole length of Mulgedium tataricum chloroplast genome was 152 401 bp, showing a typical cyclic tetrad structure containing a pair of inverted repeats (IRa and IRb), large single copy (LSC), and small single copy (SSC), and the lengths were 25 010, 83 833 and 18 548 bp, respectively. A total of 132 genes including 8 ribosomal RNA genes, 37 transfer RNA genes and 87 predicted genes were identified. SSR site analysis revealed that the genome sequence contained 21 dispersed palindromic repeats and 197 tandem repeats. The boundary analysis showed that some differences in the boundary genes among Mulgedium tataricum and other five Lactuceae species, and six Lactuceae species showed obvious expansion and contraction in IR/SC region. Phylogenetic analysis showed that 33 species from 14 genera of Compositae were grouped into two branches: the first branch includedMulgedium, Lactuca, Taraxacum, Sonchus, Anaphalis, Leontopodium, Chrysanthemum, Artemisia, Aster and Helianthus, among them, Mulgedium was most closely related toLactuca. The second clade includedCirsium, Carthamus, SaussureaandAtractylodes. The results of this study laid the new evidence and material foundation for species identification, phylogenetic evolution and resource exploitation and utilization ofMulgedium tataricum.