樟属植物ITS序列多态性分析

The ribosomal DNA internal transcribed spacer (nrDNA ITS) of 17 representative samples of Cinnamomum Schaeffer in Lauraceae was cloned and sequenced. Relevant analyses were carried out on the length variation, GC content, stability of the secondary structure of the 5.8S region, genetic distance, evolutionary pattern and phylogenetic relationship of the 87 different ITS sequences obtained. The research results showed that there was obvious polymorphism in the ITS sequence within Cinnamomum plants. Among the 87 sequences, 22 sequences were identified as pseudogene sequences, and the remaining 65 sequences were functional gene sequences; the pseudogene sequences adopted a neutral evolutionary pattern, and the variation was significantly greater than that of the functional sequences. The incomplete concerted evolution and the presence of pseudogenes in the ITS sequence in Cinnamomum plants may also occur in other groups of Lauraceae, which may be an important reason for the low success rate of the direct sequencing method of the ITS sequence in Lauraceae plants.

对樟科樟属(Cinnamomum Schaeffer) 17个代表样本的核糖体DNA内转录间隔区(nrDNA ITS)进行克隆测序。对获 得的87条不同ITS序列的长度变异、GC含量、5.8S区二级结构的稳定性、遗传距离、进化模式以及系统发育关系进行了相 关分析。研究结果显示, ITS序列在樟属植物内存在明显的多态性, 87条序列中的22条序列被鉴定为假基因序列, 其余65条 序列为功能基因序列; 假基因序列采用中性进化模式, 变异明显大于功能序列。ITS序列在樟属植物中出现一致性进化不完 全和假基因现象也可能发生在樟科其它类群中, 这可能是导致樟科植物ITS序列直接测序方式成功率低的重要原因。