Leclerc R F, Regier J C
Center for Agricultural Biotechnology, University of Maryland, College Park 20742.
J Mol Evol. 1994 Sep;39(3):244-54. doi: 10.1007/BF00160148.
Fifteen unique chorion protein-encoding cDNAs from gypsy moth have been completely sequenced. These sequences are encoded by a family of genes, based on pairwise similarity values of 78-100% within a 225-nt region. Pairwise comparisons and maximum parsimony analysis strongly support the existence of two clusters of 11 and four sequences each, called noc1 and noc2. While noc2 consists of two subclusters, there is little character support for subclusters within noc1. The highly localized character-state distribution on the parsimony tree in gypsy moth is reminiscent of that in Bombyx mori, specifically for those chorion families that have been shown to undergo gene conversion. Gene conversion thus becomes a reasonable explanation for the homogeneity of noc1 sequences and for their distinctness from noc2. The relationship between the two major clusters of chorion sequences in gypsy moth (noc1, noc2) and Bombyx mori (Bm alpha, Bm beta) has been addressed through mixed-species tree construction. All four groups cluster separately, thus providing no direct evidence of orthologous sequences. However, the occurrence of gene conversion could have eliminated such evidence. The relationship between the chorion gene tree and the species cladogenic event is discussed, as are biases in codon usage, base composition, and nucleotide transformations.
已经对来自舞毒蛾的15个独特的编码绒毛膜蛋白的cDNA进行了全序列测定。基于225个核苷酸区域内78%-100%的成对相似性值，这些序列由一个基因家族编码。成对比较和最大简约分析有力地支持了存在两个簇，分别包含11个和4个序列，称为noc1和noc2。虽然noc2由两个亚簇组成，但对于noc1内的亚簇几乎没有特征支持。舞毒蛾简约树上高度局部化的特征状态分布让人联想到家蚕中的情况，特别是对于那些已被证明经历基因转换的绒毛膜家族。因此，基因转换成为noc1序列同质性及其与noc2序列差异的合理原因。通过混合物种树构建研究了舞毒蛾（noc1、noc2）和家蚕（Bm alpha、Bm beta）中绒毛膜序列的两个主要簇之间的关系。所有四组都分别聚类，因此没有提供直系同源序列的直接证据。然而，基因转换的发生可能已经消除了此类证据。文中讨论了绒毛膜基因树与物种分支事件之间的关系，以及密码子使用、碱基组成和核苷酸转换中的偏差。
