Abstract: Insect ferritins play key roles in iron transport, response to oxidative stress and the immune response to pathogen infection and others. In this study, cDNA identification and expression of recombinant ferritin from Bemisia tabaci MED were done in order to elucidate the function of ferritin in this insect. The cDNA was amplified by RT-PCR and named BtFer1 (GenBank accession number: JX865415). The partial sequence of BtFer1 is 1 043 bp in length, encoding 224 amino acids. Sequence analysis indicated that the protein has the characteristic features of typical ferritin ironbinding region signature and a 19residue signal peptide. q-PCR assay displayed that BtFer1 was expressed in various developmental stages of B. tabaci and the expression levels in B. tabaci at the adult and 3rd instar nymphal stages were much higher than those at other stages. The expression profiling also showed that BtFer1 was up-regulated in adults treated with 1 mg/L imidacloprid. Furthermore, the BtFer1 gene was constructed into the expression vector pMAL-c2x for protein expression in prokaryotic cells and purified by amylose affinity. The results showed that the fused MBP-BtFer1 proteins could be effectively induced with 0.3 mmol/L IPTG, and the fusion protein was about 68 kDa, which was consistent with the predicted result. This study makes clear the expression levels of BtFer1 in various developmental stages and in adults of B. tabaci MED treated with lower concentration of imidacloprid, and provides a basis for further functional study of this gene. 

Key words: Bemisia tabaci MED, ferritin, gene cloning, expression profiling, prokaryotic expression, imidacloprid