栽培四倍体棉种及其二倍体祖先种的Histone3基因片段序列分析

The Sequence Analysis of Histone3 Gene Segments in Cultivated Tetraploid Cotton and Their Diploid Progenitors

组蛋白是植物基因组的重要组成部分。根据Genebank中登录的Histone3基因的全长cD NA序列,设计PCR引物,进行了异源四倍体栽培陆地棉、海岛棉及其二倍体祖先种非洲棉和雷蒙德氏棉中Histone3基因片段序列分析。不同物种中获得的基因片段分别由2个内含子、部分外显子区和3'端非翻译区组成。共存在77个单核苷酸多态性位点,其中外显子区9个,内含子Ⅰ区22个,内含子Ⅱ区21个,3'端非翻译区25个。外显子的SNP变化不影响Histone3基因的转录和翻译。分子聚类结果表明,不同物种A、D基因组的序列定向进化同源性明显,其中AvsD序列相似性为91.6%,AvsATB序列相似性为95.8%,AvsATH序列相似性为95.2%,DvsDTB序列相似性为98.5%,DvsDTH序列相似性为98.0%。A、D染色体组基因序列部分同源性分析表明,陆地棉中ATHvsDTH序列相似性为91.0%,海岛棉中ATBvsDTB序列相似性为92.5%。聚类结果再现了A、D基因组多倍体化后其基因序列与二倍体祖先种平行演化的特点以及A、D染色体组间进化速率在四倍体棉种中与二倍体祖先种中表现的一致性。本文也讨论了基因序列在不同物种中的相似性比较不仅是研究进化的有效方法,也可用于发现基因在不同物种中SNP序列及应用前景。

Histone is important component of the plant genome. The universal primer for amplifying conserved sequence of Histone3 gene in different cotton species have been designed based on registered Histone3 with whole length of (686 bp) cDNA sequence(Genebank Accession No. AF024716) in GenBank. Four studied cotton species include cultivated tetraploid (AD-genome) TM-1(G. hirsutum) and Hai7124 (G. barbadense), and their diploid progenitors G. herbaceum (A-genome) and G. raimondii (D-genome). The gene segments amplified from different cotton species also consist of two introns, partial extron and 3'-end untranscripted region. The lengths of the conserved sequence are 602 bp (from G. herbaceum, called as A), 600 bp (from G. raimondii, called as D), 609 bp (from A-subgenome of G. barbadense, called as A_(TB)), 598 bp (from D-subgenome of G. barbadense, called as D_(TB)), 602 bp (from A-subgenome of G. hirsutum, called as A_(TH)), and 599 bp (from D-subgenome of G. hirsutum, called as D_(TH)), respectively. By sequences comparison, 77 SNP (single nucleicide polymorphism) loci are found, which 9 in extron, 21 in intronⅠ, 22 in intronⅡ and 25 in 3'-end untranscripted region, respectively. SNP differences in extron didn't affect transcription and translation of Histone3 gene by inferred based on AF024716 sequence. Phylogenetic analysis showed detail evidence of orthologous (A vs D with similarity 91.6%, A vs A_(TH) with 95.2%, A vs A_(TB) with 95.8%, D vs D_(TH) with 98.0%, D vs D_(TB) with 98.5%) and homoeologous (A_(TB) vs D_(TB) with 92.5%, A_(TH) vs D_(TH) with 91.0%) relationship. The gene trees recovered reproduced the organismal history of diploid divergence followed by allotetraploid. The truth that genetic divergence between A_T and D_T is equal to that between A and D shows the evolutionary rates in diploids and polyploids are equivalent. In this paper, we also discuss that similarity analysis in different cotton species can not only be used to study evolution relationship, but also to find SNP loci with the species.