Target of rapamycin in the oriental fruit fly Bactrocera dorsalis (Hendel): its cloning and effect on yolk protein expression

Target of rapamycin (TOR), a serine/threonine protein kinase, is involved in regulating a number of growth and developmental processes of an organism, including yolk protein synthesis in insects. In this study, TOR gene was isolated, designated BdTOR (GenBank accession no. FJ167395), from the oriental fruit fly Bactrocera dorsalis (Hendel). Quantitative RT-PCR showed a higher expression of BdTOR in the pupa than in other developmental stages, as well as in ovary than in the fat body. Downregulation of BdTOR activity by rapamycin treatment and RNA interference (RNAi) in vivo resulted in a significant reduction in yolk protein transcripts in both fat body and ovary, with a substantial reduction in ovary size. However, an unexpected increase in the expression of yolk protein gene was observed in adult ovary 9 days after rapamycin treatment. Taken together, the results suggest the involvement of BdTOR in the regulation of yolk protein synthesis in B. dorsalis.