家蝇抗菌肽Diptericin基因的克隆与分析

Diptericin是抗菌肽家族中的一员, 在昆虫先天免疫系统中起着重要作用。本研究通过EST序列筛选并结合RACE技术克隆了家蝇Musca domestica的Diptericin基因（Md-Diptericin, MdDpt）cDNA序列, GenBank登录号为FJ794602。其全长410 bp, 包含一个300 bp的完整开放阅读框（ORF）, 推导的氨基酸序列C端富含甘氨酸, N端富含脯氨酸, 同源性分析表明, 它与厩蝇Stomoxys calcitrans的Diptericin A mRNA相似性最高（identity=74%）。以邻接法（Neighbor-Joining, NJ）构建的系统关系表明, 家蝇Diptericin与其他双翅目昆虫的Diptericin起源于共同的祖先, 属于Attain_C超家族（Attacin_C superfamily）。基因定量分析表明, 大肠杆菌刺激后6～12 h, 家蝇幼体MdDpt表达出现明显上调。结果提示MdDpt基因在家蝇免疫防御过程中起着重要作用。

Cloning and characterisation of the diptericin gene in Musca domestica

Diptericin gene is a member of the antimicrobial peptide family, and plays a key role in insect innate immune system. In this study, a cDNA of 410 bp encoding for a diptericin was cloned from housefly (Musca domestica) by RACE based on dbEST information, which contains a 300 bp open reading frame (ORF) and was named Md-Diptericin (MdDpt) with the GenBank accession no. FJ794602. The C-terminal of the deduced peptide consists of a glycine-rich domain, while the N-terminal consists of a proline-rich domain.The result of sequence alignment analysis showed that this gene shares 74% identity with Stomoxys calcitrans. In addition, the phylogenetic analysis also indicated that the diptericin from housefly was in the same branch with those of other species, suggesting that they originated from the same ancestor and belong to Attacin_C superfamily. Analysis of quantitative RT-PCR indicated that, after challenged with Escherichia coli, the mRNA level of MdDpt in fly larvae was up-regulated and significantly higher than that of the blank control at 6 h to 12 h post-challenge. These results suggest that MdDpt plays an important role in fly defensive system.