Rates of nucleotide substitution in angiosperm mitochondrial DNA sequences and dates of divergence between Brassica and other angiosperm lineages
Rates of nucleotide substitution in angiosperm mitochondrial DNA sequences and dates of divergence between Brassica and other angiosperm lineages
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DOI：
10.1007/pl00006502
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发表时间：
1999-05-01
影响因子：
3.9
通讯作者：
Li, WH
中科院分区：
文献类型：
--
作者：
Yang, YW;Lai, KN;Li, WH
本研究从10种豆科植物中获得了线粒体基因第一内含子的16个核苷酸序列，每个核苷酸长度约为1400 bp。利用这些新序列和5个已发表的序列，我们构建了所研究的菊科植物的系统发育树，发现nad 4基因第一内含子的核苷酸替换率很低，每年每个位点大约0.16-0.23 × 10（-9）替换，大约是nad 4外显子沉默率的一半。该内含子、ITS和IGS的替换比率约为1：23：73，其中ITS是18 S和25 S rRNA基因之间的核基因间隔区，IGS是5S rRNA基因之间的基因间隔区。小麦中不存在的禾本科植物nad 4第一内含子中的一段（335 bp）被认为是非功能序列，并被用来估计mtDNA的中性率（突变率）为0.5-0.7 × 10（-9）/位点/年，这比nad 4第一内含子其余部分的替换率高出约3倍。我们估计，单子叶-双子叶植物分裂的分歧日期为1.7亿至2.35亿年（百万年），菊科-Letterae分裂的分歧日期为1.12亿至1.56亿年，菊科-Ambidopsis分裂的分歧日期为14.5亿至20.4亿年，拟南芥-Arabideae分裂的分歧日期为14.5亿至20.4亿年。
We obtained 16 nucleotide sequences (similar to 1400 bp each) of the first intron of the mitochondrial (mt) gene for NADH subunit 4 (nad4) from 10 species of Brassicaceae. Using these new sequences and five published sequences from GenBank, we constructed a phylogenetic tree of the Brassicaceae species under study and showed that the rate of nucleotide substitution in the first intron of nad4 is very low, about 0.16-0.23 x 10(-9) substitution per site per year, which is about half of the silent rate in exons of nad4. The ratios of substitution rates in this intron, ITS, and IGS are approximately 1: 23:73, where ITS is the nuclear intergenic spacer between 18S and 25S rRNA genes and IGS is the intergenic spacer of 5S rRNA genes. A segment (335 bp) in the first intron of nad4 in Brassicaceae species that is absent in wheat was considered as a nonfunctional sequence and used to estimate the neutral rate (the rate of mutation) in mtDNA to be 0.5-0.7 x 10(-9) substitution per site per year, which is about three times higher than the substitution rate in the rest of the first intron of nad4. We estimated that the dates of divergence are 170-235 million years (Myr) for the monocot-dicot split, 112-156 Myr for the Brassicaceae-Lettuce split, 14.5-20.4 Myr for the Brassica-Ambidopsis split, and 14.5-20.4 Myr for the Arabidopsis-Arabideae split.