Abstract: Insect reproduction physiology mainly focuses on the endocrine regulation mechanism of vitellogenesis. Vitellogenesis is regulated by the juvenile hormone metabolic pathway in most insects. Analysis of the function of the key regulation elements in hormone metabolic pathway will illustrate the reproductive regulation mechanism. Juvenile hormone esterase (JHE) plays an important role in insect juvenile hormone degradation, development, metamorphosis and reproduction. We cloned partial cDNA sequence of juvenile hormone esterase gene by RT-PCR and RACE-PCR from the whitefly Bemisia tabaci MED, which was named as Btjhe and deposited in GenBank under the accession no. KC422259, encoding 552 amino acids. Btjhe showed high identity in the deduced amino acid sequence with JHE genes in Athalia rosae and Apis mellifera. The deduced amino acid sequence of Btjhe contains five conserved motifs identified in JHEs of other insect species, including a long hydrophobic binding pocket GxSxG motif that is required for the key enzymatic activity of JHE proteins. Thus, Btjhe is inferred to code juvenile hormone esterases in B. tabaci MED. The mRNA expression level of Btjhe was detected in nymphs and adults at different developmental stages by real-time quantitative PCR. The expression level was higher in adults than in nymphs and reached the peak at 11 d after eclosion. Dynamics of the mRNA expression level of Btjhe was similar with that of the vitellogenin gene (vg). The results provide insights into the molecular and physiological mechanisms underlying the regulation of whitefly reproduction.

Key words:  Bemisia tabaci MED, juvenile hormone esterase, cDNA cloning, sequence analysis, real-time quantitative PCR