Distinct developmental mechanisms influence sexual dimorphisms in the milkweed bugOncopeltus fasciatus

Abstract

Sexual dimorphism is common in animals. The most complete model of sex determination comes from Drosophila melanogaster , where the relative dosage of autosomes and X chromosomes leads indirectly to sex-specific transcripts of doublesex ( dsx ). Female Dsx interacts with a mediator complex protein encoded by intersex ( ix ) to activate female development. In males, the transcription factor encoded by fruitless ( fru ) promotes male-specific behaviour. The genetics of sex determination have been examined in a small number of other insects, yet several questions remain about the plesiomorphic state. Is dsx required for female and male development? Is fru conserved in male behaviour or morphology? Are other components such as ix functionally conserved? To address these questions, we report expression and functional tests of dsx , ix and fru in the hemipteran Oncopeltus fasciatus , characterizing three sexual dimorphisms. dsx prevents ix phenotypes in all sexes and dimorphic traits in the milkweed bug. ix and fru are expressed across the body, in females and males. fru and ix also affect the genitalia of both sexes, but have effects limited to different dimorphic structures in different sexes. These results reveal roles for i x and fru distinct from other insects, and demonstrate distinct development mechanisms in different sexually dimorphic structures.

Intersex is required for female sexual development in Hermetia illucens

“…, 2016; Just et al. , 2021). Treating with RNAi targeting to Btix in B. tabaci did not affect the morphology, but decreased the expression level of the vitellogenin gene, fecundity, eclosion rate of progeny, and body length of progeny in females (Liu et al.…”

“…In N. lugens, Nlix disruption caused both sexes external genitalia defects and impeded female-specific ovarian development (Zhang et al, 2021b). Knockdown of ix in O. fasciatus and C. metallifer affected the morphological external structure in both sexes and only in females, respectively (Aspiras et al, 2011;Gotoh et al, 2016;Just et al, 2021). Treating with RNAi targeting to Btix in B. tabaci did not affect the morphology, but decreased the expression level of the vitellogenin gene, fecundity, eclosion rate of progeny, and body length of progeny in females (Liu et al, 2020).…”

“…For example, in O. fasciatus, knock-down of dsx caused genitalia length to be shorter compared with control in both sexes, which is different from the results in D. melanogaster. However, knock-down of ix can also lead to shorter genitalia in both sexes (Just et al, 2021).…”

“…In the Hemiptera species Bemisia tabaci, reduction in Btix expression did not alter the morphology of external genitalia in females but did reduce the expression of the vitellogenin gene and influence the progeny (Liu et al, 2020). The function of ix has also been characterized in M. vitrata and Oncopeltus fasciatus (Cavaliere et al, 2009;Aspiras et al, 2011;Just et al, 2021).…”

Let's talk about sex: Mechanisms of neural sexual differentiation in Bilateria

“…Sex-specific splicing of fru and dsx is hypothesized to be a general mechanism of arthropod sex differentiation (Leelatanawit et al, 2009;Thaijongrak et al, 2022). The regulatory hierarchy upstream of these splicing events is F I G U R E 1 A phylogenetic tree showcasing the conserved nature of fru and dsx across different orders within Arthropoda (Bertossa et al, 2009;Just et al, 2023;Kientega et al, 2022;A.-M. Li et al, 2022;P. Li et al, 2017;Nguantad et al, 2020;Pomerantz & Hoy, 2015;Pomerantz & Hoy, 2015;Thaijongrak et al, 2022).…”