Abstract
RNAi based sterile insect technique (SIT) is an authentic insect management approach but requires proper target genes. During this study, spermless males were developed by interfering with germ cell differentiation and azoospermia related genes. Data demonstrates significant reductions in the target genes expressions (boul, zpg, dsxM, fzo and gas8) after oral dsRNAs administration. Knock down of target genes significantly affected the reproductive ability of males and reduced egg-hatching as compared to the control group. Furthermore, different combinations of selected gene dsRNAs (boul + zpg, boul + dsxM and zpg + dsxM) were made, which resulted up to 85.40% of male sterility. The most effective combination was selected to prepare different concentrations of dsRNA, 250, 500, 750 and 1000 ng/μl, that caused 18.97%, 38.68%, 58.02% and 85.40% male sterility, respectively. Subsequently, 1000 ng/μl of the same combination of ds-RNAs was used against differently aged adult flies (1, 5, 7, 10 days) which lead to 85.40%, 31.42%, 21.76% and 9.90% male sterility, respectively. SIT developed in this study showed that, boul + zpg combination of dsRNA feeding for 6 hours significantly reduced the number of spermatozoa and viability of sperm in 1-day-old B. dorsalis flies. In short, this study provides an effective SIT technique for long-term B. dorsalis management.
Highlights
The oriental fruit fly, Bactrocera dorsalis (Hendel) is the notorious and most dangerous horticultural pest[1]
To check whether the dsRNA of target genes will aid in developing the sterile insect technique (SIT) technology in B. dorsalis, ten genes were selected based on previous studies[4] and their homologous genes in Drosophila melanogaster were identified (Table S1)
Our results showed that 5 genes are highly expressed in the testis-specific of B. dorsalis, including boul, zpg, gas[8], fzo and double sex male (dsxM) (Fig. 1) and these testis-specific expressed genes were selected for further investigation
Summary
The oriental fruit fly, Bactrocera dorsalis (Hendel) is the notorious and most dangerous horticultural pest[1]. When traditional SIT had failed in the olive fruit fly due to an altered mating behavior in SIT-flies, genetically enhanced SIT showed great potential to control the pest population[3]. They reported that Bol gene dsRNA treated insects have strong competiveness with the wild females and caused suitable refractoriness to wild fruit fly females of olive[3]. Screening of target genes and the combination of orally administered engineered-bacteria expressing dsRNAs of different genes can lead to male sterility, establishing a SIT technique in B. dorsalis using RNAi. It confirms that RNAi is an alternative technique to radioactivity and it provides a new option for controlling other agricultural pest populations
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