鹿角菜18S rDNA序列分析及其系统发生分析

Nucleotide Analysis and Molecular Phylogenetic Affinity of 18S rDNA of Silvetia siliquosa

通过制备鹿角菜DNA,PCR扩增得到鹿角菜18S rDNA序列.测序拼接后全长1733bp,碱基A、T、C、G含量分别为25.45%、26.72%、26.72%、21.12%,序列已提交GeneBank登录号为GQ433994.该序列与NCBI数据库中其他褐藻18S rDNA序列比对后,得到可变碱基位点184个,简约信息位点161个,单碱基变化位点23个.转换碱基值Si为44,颠换碱基值Sv为30,转换颠换比值R约为1.5.NJ法构建的系统发生树显示18S rDNA在褐藻门中具有保守性,可用于辅助传统分类.PLACE数据库预测发现在鹿角菜18S rD-NA保守区有多个与水分胁迫、光诱导、Ca2+信号传导等相关转录元件,这表明18S rDNA可能参与细胞重要调控途径.

DNA of Silvetia siliquosa is extracted and the ISS ribosome DNA sequence is amplified using poly chain reaction. The sequence result shows that it is composed of 1733 nucleotides in which the A, T, C and G contents are 25.45%, 26. 72%, 26. 72% and 21.12%, respectively. The nucleotides has been submitted to the database of Gene Bank, and accession number is GQ433994. Aligning with other sequences of 18S rDNA in Phaeophyceae, it reveals that there are 184 variable sites, 161 parsimonious-information sites and 23 singleton sites. Moreover, the results show that the number of base transition, transversion and transition-transversion ratio are 44, 30 and about 1.5, respectively. The phylogenetic tree, which inferred from the 18s rDNA sequence alignment by neighbor-joining method, shows that the 18S ribosomal gene is so conserved that it il- lustrats a good prospect of application in algae identification and classification. PLACE database prediction result shows that some cis-acting regulatory DNA elements such as dehydration-responsive elements, light-regulated transcription elements, Ca^2＋ -responsive elements, et al. , are found in the nucleotide sequence. Therefore, it indicates that 18S ribosomal RNA gene may probably take part in some important regulation pathways in cell.