Parental RNA interference as a tool to study genes involved in rostrum development in the Neotropical brown stink bug, Euschistus heros.

In insects, the identity of body segments is controlled by homeotic genes and the knockdown of these genes during embryogenesis can lead to an abnormal development and/or atypical phenotypes. The main goal of this study was to investigate the involvement of labial (lab), deformed (dfd), sex comb reduced (scr), extradenticle (exd) and proboscipedia (pb) in rostrum development in the Neotropical brown stink bug Euschistus heros, using parental RNAi (pRNAi). To achieve this objective, 10-days-old adult females were first microinjected with double-stranded RNAs (dsRNA) targeting these five genes. Then, the number of eggs laid per female, the percentage of hatched nymphs with normal or abnormal phenotype and target gene silencing were evaluated. Except for the dsDfd-treatment, the number of eggs laid per female per day was not affected by the different dsRNA-treatments compared to the control (dsGFP). However, treatment with either dsLab, dsDfd, dsScr or dsExd caused a strong reduction in egg hatching. The dsExd-treatment caused no apparent change in phenotype in the nymphs while hatched nymphs from the dsDfd, dsScr and dsPb-treatment showed abnormalities in the rostrum. Particularly for the dsPb-treatment, 91% of the offspring displayed a bifurcated rostrum with a leg-like structure. Overall, these results indicate that these five genes are involved in E. heros embryonic development and that the knockdown of dfd, scr and pb leads to an abnormal development of the rostrum. Additionally, this study demonstrates the efficiency of pRNAi in studying genes involved in embryogenesis in E. heros, with clear phenotypes and a strong target gene silencing in the next generation, after treatment of the parent female adult with gene-specific dsRNA.

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