Abstract:

A lysozyme gene,MseLYS,was cloned from oriental armyworm,and then,its prokaryotic expression vector was constructed by the prokaryotic expression system,and finally,the expression pattern of this gene was detected in different stages and tissues of oriental armyworm,to provide theoretical reference for exploring the function and structure of the MseLYS and lay a foundation for further study of the antibacterial function and physiological mechanism.We cloned the sequence of the lysozyme gene MseLYS from the midgut of Mythimna separata by reverse transcription PCR(RT-PCR)and rapid amplification of cDNA ends(RACE).The open reading frame(ORF)sequence with the signal peptide removed was ligated to the expression vector pET-30a(+),and the inducible expression was carried out by IPTG.Quantitative PCR was used to detect the spatiotemporal expression pattern of this gene.Sequence analysis showed that the full length cDNA of MseLYS was 729 bp,and its ORF was 426 bp,encoding a total of 141 amino acid residues.Meanwhile,the 5'non-coding region and 3'non-coding region included 75,228 bp,respectively.The isoelectric point and molecular weight of the protein encoded by MseLYS were 7.72 and 16.13 ku,respectively.Phylogenetic tree demonstrated that MseLYS was clustered with other species' C-type lysozyme,and was highly consistent with other insect amino acid sequences,suggesting that MseLYS was a C-type lysozyme.SDS-PAGE showed that the expressed protein was consistent with the expected size,which was about 20 ku,indicating that MseLYS can be expressed efficiently in BL21(DE3).Instar expression profiling analysis illustrated that there were significant differences in the expression levels of MseLYS gene among different developmental stages of larvae,males,and females.The expression levels of MseLYS gene were higher in the late larval and pupal stages of oriental armyworm,while the expression levels were lower in other developmental stages.The tissue expression analysis results indicated that there were significant differences in the expression levels of this gene among different tissues of male adults,with higher expression levels in the fat body and thorax;this gene expression also showed significant differences among different tissues of female adults,with higher expression levels in antennae,wings,and cuticle.To sum up,the full-length sequence of MseLYS is cloned,its prokaryotic expression vector is successfully constructed,which could efficiently express the target protein,and its expression pattern is clarified in different tissues and ages.

Key words: Mythimna separata, Lysozyme, Gene cloning, Prokaryotic expression, Quantitative PCR