Conditional knockdown of transformer in sheep blow fly suggests a role in repression of dosage compensation and potential for population suppression

Identification and functional analysis of the female determiner gene in the bean bug, Riptortus pedestris

BACKGROUND

Homing-based gene drives targeting sex-specific lethal genes have been used for genetic control. Additionally, understanding insect sex determination provides new targets for managing insect pests. While sex determination mechanisms in holometabolous insects have been thoroughly studied and employed in pest control, the study of the sex determination pathway in hemimetabolous insects is limited to only a few species. Riptortus pedestris (Fabricius; Hemiptera: Heteroptera), commonly known as the bean bug, is a significant pest for soybeans. Nonetheless, the mechanism of its sex determination and the target gene for genetic control are not well understood.

RESULTS

We identified Rpfmd as the female determiner gene in the sex determination pathway of R. pedestris. Rpfmd encodes a female-specific serine/arginine-rich protein of 436 amino acids and one non-sex-specific short protein of 98 amino acids. Knockdown of Rpfmd in R. pedestris nymphs caused death of molting females with masculinized somatic morphology but did not affect male development. Knockdown of Rpfmd in newly emerged females inhibited ovary development, while maternal-mediated RNA interference (RNAi) knockdown of Rpfmd expression resulted in male-only offspring. Transcriptome sequencing revealed that Rpfmd regulates X chromosome dosage compensation and influences various biological processes in females but has no significant effect on males. Moreover, RNAi mediated knockdown of Rpfmd-C had no influence on the development of R. pedestris, suggesting that Rpfmd regulates sex determination through female-specific splicing isoforms. We also found that Rpfmd pre-mRNA alternative splicing regulation starts at the 24-h embryo stage, indicating the activation of sex differentiation.

CONCLUSION

Our study confirms that Rpfmd, particularly its female-specific isoform (Rpfmd-F), is the female determiner gene that regulates sex differentiation in R. pedestris. Knockdown of Rpfmd results in female-specific lethality without affecting males, making it a promising target for genetic control of this soybean pest throughout its development stages. Additionally, our findings improve the understanding of the sex-determination mechanism in hemimetabolous insects. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

CRISPR/Cas9 Genome Editing in the New World Screwworm and Australian Sheep Blowfly

Blowflies are of interest for medical applications (maggot therapy), forensic investigations, and for evolutionary developmental studies such as the evolution of parasitism. It is because of the latter that some blowflies such as the New World screwworm and the Australian sheep blowfly are considered major economic pests of livestock. Due to their importance, annotated assembled genomes for several species are now available. Here, we present a detailed guide for using the Streptococcus pyogenes Cas9 RNA-guided nuclease to efficiently generate both knockout and knock-in mutations in screwworm and sheep blowfly. These methods should accelerate genetic investigations in these and other closely related species and lead to a better understanding of the roles of selected genes in blowfly development and behavior.