摘 要 ：用PCR方法从石笔木(Tutcheria spectabilis Dunn )的总DNA中扩增CHS基因外显子2的部分序列以代表该基因进行研究,经克隆后测序,得到长约740～780bp的序列共12个.以EMBL数据库中得到的紫花苜蓿和欧洲赤松各一个序列作为参照,进行排序和系统树的构建分析.结果显示,所有被测定的序列同源性均高于70%,为CHS基因家族的成员,且这些序列由3大类共5种不同的基因拷贝组成:第一类家族成员因碱基的插入和缺失改变了读码框,推测已失去了CHS基因的功能,成为假基因,其中个别拷贝存在较大缺失,这在以前的研究中未见报道;第二类家族成员因活性位点的氨基酸发生突变 ,可能具有新的基因功能;第三类家族成员则具有原CHS基因的功能.综上结果,可预测, 山茶科CHS基因家族较大,且有着复杂的进化式样.
Abstract:By using PCR method, partial sequences of chalcone synthase (CHS)gene exon 2 were amplified from genomic DNA of Tutcheria spectabilis (Theaceae). After cloning and sequencing, 12 sequences ranging from 740 bp to 780bp were obtained. Comparing these sequences, with the ones of Medicago sativa and Pinus sylvestris from EMBL database, it reveals a similarity higher than 70% at the nucleotide level, and they are the members of CHS gene family. The result indicates that these sequences consist of five diffrent gene copies in three groups. In group 1,the CHS genes lost their functions because of indels of bases, then turning into pseudo-genes, which is reported here for the first time;In group 2, the gene copies provide new functions because of the mutation of the amino acid in active sites; In group 3, the copies have the same function of CHS genes. It is suggested that the CHS gene family in Theaceae is large, which has complex evolutionary mode.