亚心型扁藻叶绿体psbA基因的克隆及序列分析

Cloning and sequence analysis of psbA gene fragment from the chloroplast of Platymonas subcordiformis

psbA基因是叶绿体基因组中一个重要的光调控基因,编码光和系统Ⅱ反应中心的D1蛋白。根据叶绿体基因组序列高度保守的特性,利用莱茵衣藻(Chlamydomonas reinhardtii)psbA基因的保守序列(基因登录号:HQ667991.1)设计引物,采用PCR步移的方法从亚心型扁藻(Platymonas subcordiformis)基因组DNA中克隆到psbA基因全长(基因登录号:KF528742)。序列分析表明,亚心型扁藻psbA基因全长1939 bp,编码区长度为1062 bp,推导编码353个氨基酸,包括4个赖氨酸残基。有效密码子数显示psbA基因具有明显的密码子偏好性,并且偏好使用以A/T结尾的密码子。相对同义密码子使用度表明25个密码子在编码使用时具有偏好性,其中20个密码子以A/T碱基结尾,占到80%。其终止密码子使用了TAG。

The psbA gene coding for D1 protein in photosynthetic H reaction centre is one of the important light-regulated genes in the chloroplast genome. According to conserved motif of the homologous nucleotide sequence of psbA of Chlamydomonas reinhardtii （ Gen- Bank accession number： HQ667991.1 ） by using genome walking, 1939 bp fragment was amplified from the genome of Platymonas sub- cordiformis （GenBank accession number： KF528742）. Results showed that the coding region had 1062 bp and 353 amino acids were deduced including 4 lysines. The effective number of codons showed that codon bias existed in the psbA gene. The codons ending with A/T were frequently used. Synonymous eodon usage analysis showed that 25 codons were preferred by the psbA gene coding DNA se- quence （CDS） , and 20 codons ending with A/T, accounting for 80% of the entire CDS. The terminator codon was TAG.