菊科BRC1-like基因片段的克隆与进化分析  

Isolation and Evolution of BRC1-like Genes in Asteraceae

作　　者：陈晓丽[1] 刘勇 赵瑞艳[1] 郗琳[1] 李俊香[1] 刘凤栾[1] 赵梁军[1] 

机构地区：[1]中国农业大学观赏园艺与园林系,北京100193 [2]深圳华大基因研究院,深圳518083

出　　处：《农业生物技术学报》2013年第6期650-658,共9页Journal of Agricultural Biotechnology

基　　金：国家高技术研究发展计划(863)项目(No.2011AA10020801);教育部高等学校博士学科点专项科研基金资助课题(博导类)(No.20110008110021)

摘　　要：菊科(Asteraceae)植物在进化中产生了丰富的分枝类型,而分枝类型的多样性源于分枝相关基因的多样性。BRC1(BRANCHED1)基因作为TCP家族的成员,已被验证具有抑制侧枝伸长的功能,且该家族的基因具有较快的进化速度。本文研究了BRC1-like基因的进化模式,该基因在进化中多次复制,且不同成员受到不同的选择压,这些可能是该家族成员众多及功能多样性的基础。本研究以菊科16个种为材料,克隆得到21个BRC1-like基因的片段,均包含保守的TCP结构域,R结构域,以及ECE模体,属于TCP家族中的CYCLOIDEA1(CYC1)亚簇。结合NCBI中得到的非洲菊(Gerbera hybrid)和向日葵(Helianthus annuus)的BRC1-like基因序列,构建系统发育树,结果表明,CYC1亚簇在菊科中又分为两组,分别命名为BRC1a和BRC1b,表明此亚簇在形成后又进行了复制。利用最大似然分枝检验的方法,对其进化选择压进行检验,结果表明,BRC1b受到了强烈的纯化选择,而BRC1a受到的选择压减小。进一步运用最大似然分枝-位点检验的方法,证明BRC1a受到中性选择,而未受正选择。利用最大似然位点检验的方法,检测了BRC1-like基因片段受到纯化选择和中性选择的位点,结果表明纯化选择的位点主要集中在TCP和R结构域,以及ECE模体,证明两组基因的主要结构域在进化中被固定。菊科植物中BRC1-like基因片段的进化表明,该基因首先通过复制成为两组,而这两组受到了不同的选择压,可能会导致产生不同的功能。Diversity of branching types is produced during the evolution of Asteraceae, which is originated by the diversity of branching genes. BRCl （BRANCHEDl） genes, as the member of TCP family, are provedto play important roles in inhibition of lateral branches. BRCl-like genes were replicated during evolution, and different members were through different selective pressures, both of which may lead to the large family anddiverse functions. Twenty-one BRCl-like gene fragments were isolated from l6 Asteraceae species, which contained the conserved TCP domain, R domain and ECE motif, and were in the CYCLOIDEAl （CYCl）subclade of TCP family. With the sequences we cloned and sequences from gerbera （Gerbera hybrid） and sunflower （Helianthus annuus）（downloaded from NCBI）, phylogenetic tree were constructed. All the BRCl-like genes from Asteraceae were clustered into two groups, BRCla and BRClb, which indicated that CYCl subclade replicated and expanded during evolution. Maximum likelihood （ML） branch test was performed todetect the selective pressure, the results indicated that BRClb group evoloved under a strong purifying selection, while the BRCla group had experienced a decrease in evolutionary constrains. Results in the MLbranch-site test showed that, relaxation of selective constrains rather than positive selection was the process associated with the evolution of BRCla group. The amino acid residue targets of selection in all BRCl-likegenes were identified with ML site test model. The results indicated that, residues evolved under strong purifying selections were located in the TCP domain, R domain and ECE motif, inferred that importantdomains were fixed during evolution. The evolution of BRCI-like gene in Asteraceae indicates that two groups were clustered through replication, then these two groups underwent different selective pressures,which may lead to different functions of genes.

关 键 词：菊科 BRC1 TCP 基因复制 分子进化 

分 类 号：Q78[生物学—分子生物学]