The alternative splicing of BdTai and its involvement in the development of Bactrocera dorsalis (Hendel)

Abstract

Interest in insect metamorphosis has primarily focused on juvenile hormone (JH) and ecdysone. Compared to ecdysone signaling, the molecular action of JH is less well established because Methoprene-tolerant (Met) as the JH receptor has been identified until recently. In vitro studies have indicated that Met forms an active JH-dependent complex with one partner protein, Taiman (Tai). However, the related studies on Tai's role in insect metamorphosis are very limited. In this study, five Tai isoforms differing in C-terminal region are identified from the oriental fruit fly Bactrocera dorsalis, an important worldwide pest infesting fruits and vegetables. The spatiotemporal expression pattern analysis indicates that BdTai-A and BdTai-B are highly expressed in early larvae while BdTai-D is more abundant in middle-late larvae. Meanwhile, in vivo methoprene stress leads to dramatic expression pattern fluctuation of BdTai isoforms. The subsequent reverse genetic study reveal that all Tai isoforms (denoted as "Tai-core") depletion in larvae stage of B. dorsalis produce precocious larvae-pupae development, i.e. shortened pupation process and miniature pupae. Further knockdown of individual Tai isoform show that silence of BdTai-E causes the same phenotype as of BdTai-core RNAi. The current data suggest that BdTai-E is involved in transducing the JH signal that represses metamorphosis. Besides, isoforms should be considered when studying Tai functions.

Keywords: Juvenile hormone; Metamorphosis; Oriental fruit fly; Tai.