荠菜LEAFY同源基因的克隆与进化分析

LEAFY同源基因是高等植物花的分生组织分化的重要调节基因。根据已发表的LEAFY同源基因序列保守区设计引物,以荠菜(Capsellabursa-pastoris(L.)Medic.)基因组DNA序列为模板,克隆了一条长2866bp的LEAFY同源基因。序列分析表明,该基因含有3个外显子和2个内含子,外显子编码424个氨基酸组成的多肽。其单个外显子核苷酸序列与拟南芥(Arabidopsisthaliana)LEAFY基因同源性在90%以上,氨基酸序列同源性为86%,而与琴叶拟南芥(Ara-bidopsislyrata)的氨基酸序列同源性高达90%。不同植物物种的LEAFY同源氨基酸序列在C端高度保守,而N端则有较大程度的变异。3个外显子进化速率不同可能是由于所受选择压力不同所致。存在于荠菜CapLFY基因346位上的精氨酸突变可能是造成荠菜两种生态型花期不同的原因。

Cloning and Evolutionary Analysis of Homologous Sequences of LEAFY Gene in Capsella bursa-pastoris (Cruciferae)

LEAFY is an important regulator of floral meristems genes in higher plants.To investigate its origin and evolution,a LEAFY homologs with length of 2 866 bp was cloned from Capsella bursa-pastoris genome using the conserved primers from Arabidopsis thaliana LEAFY gene.Sequence analysis indicated three exons with the length of 457 bp,407 bp and 411 bp.These exons encoded a protein of 424 amino acids.The single exon was more than 90% homologous to A.thaliana LEAFY gene,and the amino acid homology was 86%.When compared to Arabidopsis lyrata LEAFY gene,there was 93 nucleotide substitution in the exons of C.bursa-pastoris,and 74.7% of these mutations located at the third position of codon,the amino acid homology reached 90%.Among the three exons,Ds/Dn ratio was 1.9,2.3 and 6.0.Homologous comparison indicated that the C-terminal amino acids were highly conserved among different plant species while the great variation existed in N-terminal.In addition,the Arg mutation located at 346 in CapLFY gene was speculated to be one of main reasons that caused the ecotypes with different flowering time in C.bursa-pastoris.