A study of the phylogeny of Brassica rapa, B. nigra, Raphanus sativus, and their related genera using noncoding regions of chloroplast DNA.
A study of the phylogeny of Brassica rapa, B. nigra, Raphanus sativus, and their related genera using noncoding regions of chloroplast DNA.
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DOI：
10.1016/s1055-7903(02)00026-x
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发表时间：
2002-05
影响因子：
4.1
通讯作者：
Yau-Wen Yang;P. Tai;Y. Chen;Wen-Hsiung Li
中科院分区：
文献类型：
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作者：
Yau-Wen Yang;P. Tai;Y. Chen;Wen-Hsiung Li
芸苔属有两个进化谱系：芜菁/甘蓝谱系和黑芥谱系。利用核DNA序列，如5S rRNA基因之间的基因间隔区和18 S和25 S rRNA基因之间的内转录间隔区，我们和其他人以前已经证明萝卜是密切相关的黑谱系。本研究测定了7种植物叶绿体trnT和trnF之间以及trnD和trnT之间的非编码区序列。sativus与rapa/oleracea谱系的关系比与nigra谱系的关系更密切。从核DNA和叶绿体DNA的相互矛盾的结果支持的假设，萝卜是来自之间的杂交的rapa/oleracea和黑谱系。我们估计这一杂交事件的日期是两个芸苔属谱系之间的分歧时间的60%。此外，研究了核苷酸取代的模式和速率。在这些AT含量高的非编码区中，颠换比转换多。此外，一个位点上的置换之间的颠换比例随着其相邻两个核苷酸的A+T含量的增加而增加。当两条DNA链上相邻碱基均为A或T时，直接5′嘧啶对取代模式也有影响。在trnL组I内含子中的核苷酸取代率仅为trnT-trnF片段中附近基因间间隔区中的核苷酸取代率的约三分之一。在芜菁/甘蓝谱系中的核苷酸替换率至少是在黑谱系中的1.5倍。
There are two evolutionary lineages in the genus Brassica: the rapa/oleracea lineage and the nigra lineage. Using nuclear DNA sequences such as the intergenic spacer between 5S rRNA genes and the internal transcribed spacer between 18S and 25S rRNA genes, we and others had previously demonstrated that Raphanus sativus is closely related to the nigra lineage. In the present study, we sequenced the chloroplast noncoding region between trnT and trnF and that between trnD and trnT in seven species and showed that R. sativus is more closely related to the rapa/oleracea lineage than to the nigra lineage. The conflicting results from nuclear DNA and chloroplast DNA support the hypothesis that Raphanus was derived from a hybridization between the rapa/oleracea and the nigra lineages. We estimated the date of this hybridization event to be 60% of the divergence time between the two Brassica lineages. In addition, the pattern and rate of nucleotide substitution were studied. There were more transversions than transitions in these noncoding regions, which have a high AT content. Furthermore, the proportion of transversions among the substitutions at a site increases with increasing A+T content of its two adjacent nucleotides. An influence of immediate 5′pyrimidine on substitution pattern is also observed when both adjacent bases in the two DNA strands are A or T. The rate of nucleotide substitution in the trnL group I intron is only about one third of the rate in the nearby intergenic spacers in the trnT–trnF fragment. The rate of nucleotide substitution in the rapa/oleracea lineage is at least 1.5 times that in the nigra lineage.