| Summary: | 碩士 === 國立中興大學 === 昆蟲學系所 === 100 === The oriental fruit fly, Bactrocera dorsalis (Hendel), invades more than 150 fruit crops; it causes serious damage to fruits and leads to huge economic loss in Taiwan. Owing to the number of female flies is directly correlated to crops; a comprehensive understanding of sexual determination will be useful to find a new way to reducing female flies in the field. In the tephritid flies, transformer (tra) is a switch in female sex-determination. To learn more matter of this system, the expression patterns of sex-related genes including tra, transformer-2 (tra-2), doublesex (dsx) and yolk protein gene (Bdyp1) in Bactrocera dorsalis were examined in this study. RNA preparations from the different developmental stages of the oriental fruit flies were extracted to detect the expressions of these genes by Reverse transcription polymerase chain reaction (RT-PCR). High levels of Bdtraf observed in both unfertilized and fertilized eggs and consist with the previous observation from Ceratitis capitata that the female will deposit traf mRNA into eggs for its auto-regulatory function in embryonic stage. In the larval and pupal stage, many gender characters are still indefinite, expression levels of these sex-related genes are relatively low compared to those of adults. After eclosion, the expressions of Bdtraf, Bddsxf and Bdyp1 in female and the expression of Bddsxm in male are increasing with age. The phenomena indicate these products are functional and critical in sex differential pathways. TRA-2 is a protein present in both male and female, its expression level is constant in all stages as expected. Two RNA interference (RNAi) experiments were performed for Bdtra functional analyses. In the feeding experiment, 13 male and 10 female flies enclosed successful after the Bdtra siRNA treatment. However, all flies are normal in appearance, and the sex ratio of the F1 offspring of treated males close to 1:1 without expected intersex or pseudomales detected. In addition, Bdtra doubles-strand RNA covering exon 2 to exon 4 was prepared, and injected into 68 early pupae. Total 16 male and 19 female flies were successful eclosion. Eight RNAi treated female had deformed ovipositor; six of these female were unable to lay eggs. Most of male adults possessed normal external genitalia, but some individuals did not have offspring. No morphological changes were detected on ovaries or spermaries of Bdtra dsRNA treated flies.
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