基于Cyt b基因序列分析的松毛虫种群遗传结构研究

为了揭示松毛虫种群的遗传结构,采用DNA序列测定的方法测定了松毛虫不同种群的线粒体细胞色素b (Cyt b)基因的部分序列,并利用分子生物学软件分析其核苷酸组成、转换和颠换、氨基酸组成、遗传距离及亲缘关系。结果显示:在获得的Cyt b 基因387bp的序列中碱基A,T,C,G平均含量分别为40.1%、33.5%、9.5%、16.9%,A+T含量明显高于G+C含量表现出强烈的A、T偏向性,密码子第3位点的A+T含量高达86.5%,这种偏向性在种群间无明显差异。碱基替换主要发生在密码子第三位,转换大于颠换,且种群内替换高于种群间。该序列片段中共有39个核甘酸位点发生变异,遗传距离为0.000-0.100,显示出较小的遗传变异。蛋白质氨基酸由除谷氨酸以外的19种氨基酸组成。聚类分析结果表明马尾松毛虫和油松毛虫亚种遗传距离较近,种群间的遗传分化与生态环境有关。

Genetic structure of Pine caterpillars (Dendrolimus )populations based on the analysis of Cyt b gene sequences

As the major forest pest in China, Dendrolimus includes Dendrolimus punctatus Walker, D. tabulaeformis Tsai et Liu, D. spectabilis Butler, D. superans Butler, D. houi Lajonquiere and D. kikuchii Matsumura. During sequential outbreaks, economic damage was serious and the forest appeared to be burned. So a large number of studies were (carried out at different levels but the research concerning the genetic variation and differentiation of populations based on a single specific gene mutation has not been reported. In order to clarify the genetic structure of the populations of Dendrolimus, and provide the scientific basis for prevention and treatment of Dendrolimus, a fragment with 387 bp of the mitochondrial cytochrome b (Cyt b) gene sequence in different populations of D. punctatus Walker, D. spectabilis Butler and D. tabulaeformis Tsai et Liu was amplified and sequenced. Nucleotide composition, transitions and transversions, amino acid composition, genetic distance, and the phylogenetic relationship were analyzed with molecular biology software. The results indicated that the average contents of A, T, C and G were 40.1%, 33.5%, 9.5% and 16.9%, respectively, and the contents of A+T 73.6% were obviously higher than that of C+G 26.4%. Cyt b exhibits an A/T bias across all sites which was the most prominent at the third position of codon with the highest content of 86.5% but only 1.1% of C at the same position. There was no significant difference for A/T bias in the populations. Nucleotide substitution occurred mostly at the third position. Transitions were greater than transversions, while substitutions of intraspecific populations were higher than interspecific populations. Thirty nine nucleotide sites and eleven amino acids showed mutation in this sequence fragment and the variability were 10.1% and 8.5%. Nucleotide sequences and amino acid sequences in genetic distance were 0.000-0.100 and 0.000-0.086, indicating a low genetic variation. The amino acid sequences were believed to be more accurate than nucleotide sequences in genetic distance. Polypeptide is composed of nineteen amino acids except for glutamic acid and amino acid differences have little to do with populations. The most common amino acids and codons are lysine and asparagine .The average content of AAA and AAU is 15.00% and 10.63%, respcetively. Cluster analysis showed that the genetic distance between D. punctatus Walker and D. tabulaeformis is relatively close, while genetic differentiation exists between D. punctatus Walker and D. spectabilis Butler. The population genetic differentiation was related to ecological environment. These results provided a basic molecular biology clue to the studies on population genetics and ecological control of Dendrolimus.