四个DNA 片段在山茶属分子系统学研究中的应用

选取山茶属14 个组中的10 组21 种植物对目前常用于属内种间的4 个DNA 片段( ITS、waxy 、trnLF
、rpL16) 进行序列测定。结果表明: ( 1) 来自叶绿体基因组的2 个片段( trnL- F、rpL 16) 其PCR 扩增和
测序都很容易, 但两者的进化速率都非常慢, 序列矩阵只有很少信息位点( trnL-F 含9 个, rpL16 为20
个) , 不能提供必要的系统发育信息。( 2) 来自核基因组的ITS 片段其PCR 产物比较容易获得, 但其序列
的测定存在较多问题。( 3) waxy 是来自核基因组的另一个片段, 其PCR 扩增因受模板DNA 的数量和质量
的影响很大而有一定难度, 但其进化速率较快, 序列矩阵具有较多信息位点( 92 个) , 并且在山茶属是单
拷贝, 这对于解决山茶属这类具有许多近缘物种的类群的系统关系有重要价值。基于tsnL- F、rpL16 和
waxy 三组数据所建分子系统树支持山茶属为一单系, 但属下系统由于取样等原因有待进一步研究。

The Application of Four DNA Sequences to Studying Molecular Phylogeny of Camellia ( Theaceae) *

Four DNA sequences) ITS, waxy , trnL- F, and rpL 16 have been used to resolve the inter- species relationships
of twenty- one species representing 10 out of the 14 sections in Camellia. The results indicated that: ( 1) PCR amplification
and sequencing were easy for trnL- F and rpL16 sequences, however, the divergence rates of the two chloroplast
sequences are too slow with few phylogenetically informative sites in data matrix es ( 9 sites in trnL- F and 20 sites in
rpL 16) , so they could not provide enough phylogenetic information; ( 2) The PCR products of ITS were easily obtained,
but there were still many problems in sequencing; ( 3) The waxy gene, another sequence from the nuclear genome, has
significant values in resolving the infrageneric relationships in Camellia. The divergence rate is faster than aforementioned
sequences. There were more informative sites ( 92) in data matrix though PCR amplification was difficult because it is affected
by quantity and quality of template DNA and it is a single copy gene in Camellia. The present study indicated that
the waxy gene had great potential values in the systematic study of Camellia while other three sequences are unfitted to resolve
the problem. The results of our DNA analysis of three segments support that the genus Camellia is a monophyletic
group, but the inter- species relationships is still needed more study.