木毒蛾钙黏蛋白基因的克隆及其表达与结构特点分析OA北大核心

[Objective]The molecular characteristics and expression pattern of cadherin in Lymantria xylina(LxCad),as well as its molecular interaction mechanism with Cry1Ac toxin were investigated to provide a reference for in-depth study of Cry toxin receptor proteins.[Method]Using the midgut cDNA of L.xylina larvae as the template,the LxCad gene was cloned by RT-PCR and then bio-logically analyzed.Its expression pattern in different instars and tissues(head,midgut and cuticula)was unveiled by real-time quantitative PCR(qRT-PCR).The medium lethal concentration(LC50)of Cry1Ac protein on the 2nd instar larvae of L.xylina was determined by virulence assay,and the expression of LxCad after Cry1Ac stress at LC50 was analyzed by qRT-PCR.Based on the ho-mology modeling of LxCad and Cry1Ac 3D model obtained from Protein Data Bank,the amino acid residues for their interactions were predicted by protein-protein docking analysis under computer simulation.[Result]The open reading frame(ORF)of the Lx-Cad gene(GenBank ID:MN380035.1)cloned from midgut is 5 172 bp in length,with the encoded protein containing 1 723 amino acids;it has a theoretical molecular weight of 194 ku and an isoelectric point of 4.24.The inferred amino acid sequences included 1 signal sequence(SIG),1 proprotein region(PRO),12 cadherin repeat regions(CR),1 membrane-proximal region(MPR),1 transmembrane domain(TM)and 1 cytomere(CYT).Sequence alignment and evolutionary tree analysis showed that the LxCad gene was most closely related to the Cad in L.dispar.The results of qRT-PCR showed that LxCad was mainly distributed in the larvae intestine,with the highest expression level in the 5th instar larvae,followed by the 6th instar larvae,and relatively less expression in the junior larvae.Under the Cry1Ac toxin stress,the expression of LxCad in the 2nd instar larvae was significantly up-regulated in comparison to the untreated control group.Protein-protein docking analysis showed that multiple amino acid residues located in the PRO,CR8 and CR9,which involved in the interaction of Cry1Ac toxin and receptor LxCad through hydrogen bonding.[Conclu-sion]LxCad may be a potential receptor protein of Cry1Ac.