Molecular cloning and functional characterization of the sex-determination gene doublesex in the sexually dimorphic broad-horned beetle Gnatocerus cornutus (Coleoptera, Tenebrionidae)

Understanding the genetics of sex determination in insects and its relevance to genetic pest management

Sex determination pathways regulate male and female-specific development and differentiation and offer potential targets for genetic pest management methods. Insect sex determination pathways are comprised of primary signals, relay genes and terminal genes. Primary signals of coleopteran, dipteran, hymenopteran and lepidopteran species are highly diverse and regulate the sex-specific splicing of relay genes based on the primary signal dosage, amino acid composition or the interaction with paternally inherited genes. In coleopterans, hymenopterans and some dipterans, relay genes are Transformer orthologs from the serine-arginine protein family that regulate sex-specific splicing of the terminal genes. Alternative genes regulate the splicing of the terminal genes in dipterans that lack Transformer orthologs and lepidopterans. Doublesex and Fruitless orthologs are the terminal genes. Doublesex and Fruitless orthologs are highly conserved zinc-finger proteins that regulate the expression of downstream proteins influencing physical traits and courtship behaviours in a sex-specific manner. Genetic pest management methods can use different mechanisms to exploit or disrupt female-specific regions of different sex determination genes. Female-specific regions of sex determination genes can be exploited to produce a lethal gene only in females or disrupted to impede female development or fertility. Reducing the number of fertile females in pest populations creates a male-biased sex ratio and eventually leads to the local elimination of the pest population. Knowledge on the genetic basis of sex determination is important to enable these sex determination pathways to be exploited for genetic pest management.

Transcriptomic comparison analysis across seven developmental stages of the Triatoma rubrofasciata, a vector of Chagas disease

BACKGROUND

Triatoma rubrofasciata is an obligate hematophagous insect and a primary vector of Trypanosoma cruzi, the etiological agent of Chagas disease, with a widespread global distribution. In addition to Try. cruzi, T. rubrofasciata also serves as a vector for various other pathogens, including Try. lewisi, Try. conorhini, and Bartonella species. Despite its increasing epidemiological relevance in the transmission of multiple diseases, research on T. rubrofasciata remains limited.

RESULTS

Differentially expressed genes (DEGs) were associated with growth, development, carbohydrate metabolism, and immunity. Notably, homeobox protein genes, including homeobox protein Nkx-6.2-like, homeobox protein abdominal-B isoform X1, homeobox protein Hox-A3-like, and Hox-B4-like, along with E3 ubiquitin protein ligase genes and sexual differentiation-related genes, such as male-specific lethal 1-like 1 isoform X3 (MSL), transformer-2 protein homolog beta-like isoform X2 (tra-2), and doublesex- and mab-3-related transcription factor A2-like (dsx), were highly expressed in the egg stage. Additionally, venom-related genes, including venom histidine phosphatase-like protein 1 and venom serine carboxypeptidase-like, were predominantly expressed in nymphal stages 4 and 5, while cytochrome P450 CYP425A1v2 exhibited high expression levels in the adult stages. Among these DEGs, we propose that homeobox protein genes, dsx, tra-2, and others may serve as candidate genes involved in growth, development, and sexual differentiation. This study provides valuable insights into gene expression dynamics during T. rubrofasciata development and establishes a foundation for future functional research on this species.

CONCLUSIONS

In this study, we sequenced the complete developmental stages of T. rubrofasciata using HiSeq technology. Our findings offer novel insights into the molecular mechanisms underlying development and sex regulation in this species. Furthermore, the identified differentially expressed genes (DEGs) may serve as potential targets for innovative pest control strategies.

Challenges in developing a split drive targeting dsx for the genetic control of the invasive malaria vector Anopheles stephensi

BACKGROUND

Anopheles stephensi is a competent malaria vector mainly present in southern Asia and the Arabian Peninsula. Since 2012, it has invaded several countries of eastern Africa, creating an emerging risk of urban transmission. Urgent efforts are required to develop novel and more efficient strategies for targeted vector control. CRISPR/Cas9-based homing gene drives have been proposed as attractive alternative strategies. Gene drives have the potential to spread a desired trait through a population at higher rates than via normal Mendelian inheritance, even in the presence of a fitness cost. Several target genes have been suggested and tested in different mosquito vector species such as Anopheles gambiae and Aedes aegypti. Several promising suppression drives have been developed in An. gambiae that target the sex determination gene doublesex (dsx).

METHODS

In this study, a geographically confineable gene drive system targeting dsx was developed (dsxgRNA). Here, a transgenic line which expresses Cas9 under the control of the endogenous zpg promoter was generated. Separately a transgenic line which expresses a gRNA targeting the female specific exon of dsx was inserted into that same target site. The reproductive fitness of males and females heterozygous and homozygous for this element was determined. A series of experimental crosses was performed to combine the two elements and assess the homing rate of the dsx element in a split drive system.

RESULTS

The drive was able to home in a super-Mendelian rate comparable to those obtained by an autonomous drive in this species. Although inheritance rates as high as 99.8% were observed, potentially providing very potent gene drive, dominant effects on male and female fertility were observed, which would be sufficient to hinder spread of such a drive. Molecular analysis indicated that the gRNA expressing insertion disrupted normal splicing of dsx.

CONCLUSIONS

These results should be considered when proposing the viability of dsx as a target gene for a population suppression gene drives in Anopheles stephensi. Although high homing rates were observed, the fitness defects found in both males and females carrying the transgene would likely prohibit this drive from functioning in the field.

Induction of male-like mandibles in XX individuals of a stag beetle by gene knockdown of a feminizer gene transformer

Males and females share most of the genome, but many animals show different phenotypes between the sexes, known as sexual dimorphism. Many insect species show extreme sexual dimorphism, including beetles with "weapon traits" represented by extremely developed horns and mandibles. Existing studies of sex-specific development of beetle weapon traits suggest that sex-specific gene expression plays an important role. On the other hand, contributions of the Y-chromosome, which may potentially carry genes necessary for male development, to weapon trait expression have not been examined. In holometabolous insects, including beetles, the feminizing gene transformer (tra) is roughly conserved in its feminizing function. Only females express a functional isoform of Tra, which causes female differentiation. Knocking down tra in females leads to male tissue differentiation, enabling us to analyze male phenotypes in individuals lacking a Y-chromosome (XX-males). In this study, we investigate whether the Y-chromosome is necessary for stag beetles to express male-specific weapon traits by comparing tra-knockdown-induced XX-males with natural XY males. We show that XX-males could express weapons (enlarged mandibles) as in XY-males. These results suggest that the Y-chromosome does not have a major role in weapon trait expression in this species.

Transcriptomic Evidence for Cell-Autonomous Sex Differentiation of the Gynandromorphic Fat Body in the Silkworm, Bombyx mori

The classic model of sex determination in insects suggests that they do not have sex hormones and that sex is determined in a cell-autonomous manner. On the other hand, there is accumulating evidence that the development of secondary sexual traits is controlled in a non-cell-autonomous manner through external factors. To evaluate the degrees of the cell-autonomous and non-cell-autonomous regulation of secondary sexual trait development, we analyzed the dynamics of the sexually dimorphic transcriptome in gynandromorphic individuals of the mo mutant strain in the silkworm Bombyx mori. The silkworm possesses a female heterogametic sex-determination system (ZZ = male/ZW = female), where the master regulatory gene for femaleness, Feminizer (Fem), is located in the W chromosome. As a secondary sexual trait, we focused on the fat body, which shows remarkable differences between the sexes during the last instar larval stage. A comparison of the transcriptomes between the fat bodies of male and female larvae identified 232 sex-differentially expressed genes (S-DEGs). The proportions of ZZ and ZW cells constituting the fat body of the gynandromorphic larvae were calculated according to the expression level of the Fem. Based on the obtained values, the expression level of each S-DEG was estimated, assuming that the levels of S-DEG expression were determined according to the proportion of ZZ and ZW cells. The estimated expression levels of 207 out of 232 S-DEGs were strongly correlated with the corresponding S-DEG expression level of the gynandromorphic fat body, determined by RNA-seq. These results strongly suggest that most of the sexually dimorphic transcriptome in the fat body is regulated in a cell-autonomous manner.

Transcriptomic and functional screening of weapon formation genes implies significance of cell adhesion molecules and female-biased genes in broad-horned flour beetle

For understanding the evolutionary mechanism of sexually selected exaggerated traits, it is essential to uncover its molecular basis. By using broad-horned flour beetle that has male-specific exaggerated structures (mandibular horn, head horn and gena enlargement), we investigated the transcriptomic and functional characters of sex-biased genes. Comparative transcriptome of male vs. female prepupal heads elucidated 673 sex-biased genes. Counter-intuitively, majority of them were female-biased (584 genes), and GO enrichment analysis showed cell-adhesion molecules were frequently female-biased. This pattern motivated us to hypothesize that female-biased transcripts (i.e. the transcripts diminished in males) may play a role in outgrowth formation. Potentially, female-biased genes may act as suppressors of weapon structure. In order to test the functionality of female-biased genes, we performed RNAi-mediated functional screening for top 20 female-biased genes and 3 genes in the most enriched GO term (cell-cell adhesion, fat1/2/3, fat4 and dachsous). Knockdown of one transcription factor, zinc finger protein 608 (zfp608) resulted in the formation of male-like gena in females, supporting the outgrowth suppression function of this gene. Similarly, knockdown of fat4 induced rudimental, abnormal mandibular horn in female. fat1/2/3RNAi, fat4RNAi and dachsousRNAi males exhibited thick and/or short mandibular horns and legs. These cell adhesion molecules are known to regulate tissue growth direction and known to be involved in the weapon formation in Scarabaeoidea beetles. Functional evidence in phylogenetically distant broad-horned flour beetle suggest that cell adhesion genes are repeatedly deployed in the acquisition of outgrowth. In conclusion, this study clarified the overlooked functions of female-biased genes in weapon development.

The draft genome sequence of the Japanese rhinoceros beetle Trypoxylus dichotomus septentrionalis towards an understanding of horn formation

The Japanese rhinoceros beetle Trypoxylus dichotomus is a giant beetle with distinctive exaggerated horns present on the head and prothoracic regions of the male. T. dichotomus has been used as a research model in various fields such as evolutionary developmental biology, ecology, ethology, biomimetics, and drug discovery. In this study, de novo assembly of 615 Mb, representing 80% of the genome estimated by flow cytometry, was obtained using the 10 × Chromium platform. The scaffold N50 length of the genome assembly was 8.02 Mb, with repetitive elements predicted to comprise 49.5% of the assembly. In total, 23,987 protein-coding genes were predicted in the genome. In addition, de novo assembly of the mitochondrial genome yielded a contig of 20,217 bp. We also analyzed the transcriptome by generating 16 RNA-seq libraries from a variety of tissues of both sexes and developmental stages, which allowed us to identify 13 co-expressed gene modules. We focused on the genes related to horn formation and obtained new insights into the evolution of the gene repertoire and sexual dimorphism as exemplified by the sex-specific splicing pattern of the doublesex gene. This genomic information will be an excellent resource for further functional and evolutionary analyses, including the evolutionary origin and genetic regulation of beetle horns and the molecular mechanisms underlying sexual dimorphism.

doublesex Controls Both Hindwing and Abdominal Mimicry Traits in the Female-Limited Batesian Mimicry of Papilio memnon

Papilio butterflies are known to possess female-limited Batesian mimicry polymorphisms. In Papilio memnon, females have mimetic and non-mimetic forms, whereas males are monomorphic and non-mimetic. Mimetic females are characterized by color patterns and tails in the hindwing and yellow abdomens. Recently, an analysis of whole-genome sequences has shown that an approximately 160 kb region of chromosome 25 is responsible for mimicry and has high diversity between mimetic (A) and non-mimetic (a) alleles (highly diversified region: HDR). The HDR includes three genes, UXT, doublesex (dsx), and Nach-like, but the functions of these genes are unknown. Here, we investigated the function of dsx, a gene involved in sexual differentiation, which is expected to be functionally important for hindwing and abdominal mimetic traits in P. memnon. Expression analysis by reverse transcription quantitative PCR (RT-qPCR) and RNA sequencing showed that mimetic dsx (dsx-A) was highly expressed in the hindwings in the early pupal stage. In the abdomen, both dsx-A and dsx-a were highly expressed during the early pupal stage. When dsx was knocked down using small interfering RNAs (siRNAs) designed in the common region of dsx-A and dsx-a, a male-like pattern appeared on the hindwings of mimetic and non-mimetic females. Similarly, when dsx was knocked down in the abdomen, the yellow scales characteristic of mimetic females changed to black. Furthermore, when dsx-a was specifically knocked down, the color pattern of the hindwings changed, as in the case of dsx knockdown in non-mimetic females but not mimetic females. These results suggest that dsx-a is involved in color pattern formation on the hindwings of non-mimetic females, whereas dsx-A is involved in hindwing and abdominal mimetic traits. dsx was involved in abdominal and hindwing mimetic traits, but dsx expression patterns in the hindwing and abdomen were different, suggesting that different regulatory mechanisms may exist. Our study is the first to show that the same gene (dsx) regulates both the hindwing and abdominal mimetic traits. This is the first functional analysis of abdominal mimicry in butterflies.

Tissue-specific developmental regulation and isoform usage underlie the role of doublesex in sex differentiation and mimicry in Papilio swallowtails

Adaptive phenotypes often arise by rewiring existing developmental networks. Co-option of transcription factors in novel contexts has facilitated the evolution of ecologically important adaptations. doublesex (dsx) governs fundamental sex differentiation during embryonic stages and has been co-opted to regulate diverse secondary sexual dimorphisms during pupal development of holometabolous insects. In Papilio polytes, dsx regulates female-limited mimetic polymorphism, resulting in mimetic and non-mimetic forms. To understand how a critical gene such as dsx regulates novel wing patterns while maintaining its basic function in sex differentiation, we traced its expression through metamorphosis in P. polytes using developmental transcriptome data. We found three key dsx expression peaks: (i) eggs in pre- and post-ovisposition stages; (ii) developing wing discs and body in final larval instar; and (iii) 3-day pupae. We identified potential dsx targets using co-expression and differential expression analysis, and found distinct, non-overlapping sets of genes-containing putative dsx-binding sites-in developing wings versus abdominal tissue and in mimetic versus non-mimetic individuals. This suggests that dsx regulates distinct downstream targets in different tissues and wing colour morphs and has perhaps acquired new, previously unknown targets, for regulating mimetic polymorphism. Additionally, we observed that the three female isoforms of dsx were differentially expressed across stages (from eggs to adults) and tissues and differed in their protein structure. This may promote differential protein-protein interactions for each isoform and facilitate sub-functionalization of dsx activity across its isoforms. Our findings suggest that dsx employs tissue-specific downstream effectors and partitions its functions across multiple isoforms to regulate primary and secondary sexual dimorphism through insect development.

Characterization of the First W-Specific Protein-Coding Gene for Sex Identification in Helicoverpa armigera

Helicoverpa armigera is a globally-important crop pest with a WZ (female)/ZZ (male) sex chromosome system. The absence of discernible sexual dimorphism in its egg and larval stages makes it impossible to address any sex-related theoretical and applied questions before pupation unless a W-specific sequence marker is available for sex diagnosis. To this end, we used one pair of morphologically pre-sexed pupae to PCR-screen 17 non-transposon transcripts selected from 4855 W-linked candidate reads identified by mapping a publicly available egg transcriptome of both sexes to the male genome of this species and detected the read SRR1015458.67499 only in the female pupa. Subsequent PCR screenings of this read and the previously reported female-specific RAPD (random amplified polymorphic DNA) marker AF18 with ten more pairs of pre-sexed pupae and different annealing positions and/or temperatures as well as its co-occurrence with the female-specific transcript splicing isoforms of doublesex gene of H. armigera (Hadsx) and amplification and sequencing of their 5′ unknown flanking sequences in three additional pairs of pre-sexed pupae verified that SRR1015458.67499 is a single copy protein-coding gene unique to W chromosome (named GUW1) while AF18 is a multicopy MITE transposon located on various chromosomes. Test application of GUW1 as a marker to sex 30 neonates of H. armigera yielded a female/male ratio of 1.14: 1.00. Both GUW1 and Hadsx splicing isoforms assays revealed that the H. armigera embryo cell line QB-Ha-E-1 is a male cell line. Taken together, GUW1 is not only a reliable DNA marker for sexing all stages of H. armigera and its cell lines, but also represents the first W-specific protein-coding gene in lepidopterans.

Mutation of doublesex in Hyphantria cunea results in sex-specific sterility

BACKGROUND

The gene doublesex (dsx) plays pivotal roles in sex determination and controls sexually dimorphic development in certain insects. Importantly, it also displays a potential candidate target for pest management due to its sex-specific splicing. Therefore, we used CRISPR/Cas9-mediated gene disruption to investigate the function of dsx in Hyphantria cunea, an invasive forest pest.

RESULT

In the present study, we identified the dsx gene from H. cunea which showed a sex-biased expression pattern that was different from other lepidopteran insects. Referring to sex-specific functional analyses in Bombyx mori, we performed a site-specific knockout of the Hcdsx gene by using a CRISPR/Cas9 system, which induced severe abnormalities in external genitalia and some incomplete sex reversal phenotypes, which in turn led to reduced sex-specific fecundity. An alternative splicing pattern of Hcdsx was altered by CRISPR/Cas9-induced mutation, and alterations in splicing affected expression of downstream genes encoding pheromone binding protein 1, vg1 and vg2 (encoding vitellogenin), which contributed to the sex-specific sterility phenotypes in the Hcdsx mutants.

CONCLUSION

The Hcdsx gene plays important roles in sexual differentiation in H. cunea. Disruption of Hcdsx induced sex-specific sterility, demonstrating a potential application in control of this pest. © 2019 Society of Chemical Industry.

A specific type of insulin-like peptide regulates the conditional growth of a beetle weapon

Evolutionarily conserved insulin/insulin-like growth factor (IGF) signaling (IIS) has been identified as a major physiological mechanism underlying the nutrient-dependent regulation of sexually selected weapon growth in animals. However, the molecular mechanisms that couple nutritional state with weapon growth remain largely unknown. Here, we show that one specific subtype of insulin-like peptide (ILP) responds to nutrient status and thereby regulates weapon size in the broad-horned flour beetle Gnatocerus cornutus. By using transcriptome information, we identified five G. cornutus ILP (GcorILP1-5) and two G. cornutus insulin-like receptor (GcorInR1, -2) genes in the G. cornutus genome. RNA interference (RNAi)-mediated gene silencing revealed that a certain subtype of ILP, GcorILP2, specifically regulated weapon size. Importantly, GcorILP2 was highly and specifically expressed in the fat body in a condition-dependent manner. We further found that GcorInR1 and GcorInR2 are functionally redundant but that the latter is partially specialized for regulating weapon growth. These results strongly suggest that GcorILP2 is an important component of the developmental mechanism that couples nutritional state to weapon growth in G. cornutus. We propose that the duplication and subsequent diversification of IIS genes played a pivotal role in the evolution of the complex growth regulation of secondary sexual traits.

Disruption of sex-specific doublesex exons results in male- and female-specific defects in the black cutworm, Agrotis ipsilon

BACKGROUND

Doublesex (dsx), the downstream gene in the insect sex-determination pathway, is a key regulator of sexually dimorphic development and behavior across a variety of insects. Manipulating expression of dsx could be useful in the genetic control of insects. However, information on the sex-specific function of dsx in non-model insects is lacking.

RESULTS

In this work, we isolated a dsx homolog, which is alternatively spliced into six female-specific and one male-specific isoforms, from an important agricultural pest, the black cutworm, Agrotis ipsilon. Studies on the expression of sex-specific Aidsx mRNA during embryonic development showed that the sixth hour post oviposition is the key stage for sex determination in A. ipsilon. Functional analysis of Aidsx was conducted using a CRISPR/Cas9 system targeting female- and male-specific Aidsx exons. Disruptions of sex-specific Aidsx exons resulted in sex-specific, sexually dimorphic defects in external genitals, gonads and antennae, and expression of sex-specific genes as well as production of offspring in both sexes.

CONCLUSION

Our results not only demonstrate that dsx is a key player determining A. ipsilon sexually dimorphic traits, but also provide a potential method for the genetic control of this pest. © 2018 Society of Chemical Industry.

Genetic architecture and sex-specific selection govern modular, male-biased evolution of doublesex

doublesex regulates early embryonic sex differentiation in holometabolous insects, along with the development of species-, sex-, and morph-specific adaptations during pupal stages. How does a highly conserved gene with a critical developmental role also remain functionally dynamic enough to gain ecologically important adaptations that are divergent in sister species? We analyzed patterns of exon-level molecular evolution and protein structural homology of doublesex from 145 species of four insect orders representing 350 million years of divergence. This analysis revealed that evolution of doublesex was governed by a modular architecture: Functional domains and female-specific regions were highly conserved, whereas male-specific sequences and protein structures evolved up to thousand-fold faster, with sites under pervasive and/or episodic positive selection. This pattern of sex bias was reversed in Hymenoptera. Thus, highly conserved yet dynamic master regulators such as doublesex may partition specific conserved and novel functions in different genic modules at deep evolutionary time scales.

Intrasexually selected weapons

We propose a practical concept that distinguishes the particular kind of weaponry that has evolved to be used in combat between individuals of the same species and sex, which we term intrasexually selected weapons (ISWs). We present a treatise of ISWs in nature, aiming to understand their distinction and evolution from other secondary sex traits, including from 'sexually selected weapons', and from sexually dimorphic and monomorphic weaponry. We focus on the subset of secondary sex traits that are the result of same-sex combat, defined here as ISWs, provide not previously reported evolutionary patterns, and offer hypotheses to answer questions such as: why have only some species evolved weapons to fight for the opposite sex or breeding resources? We examined traits that seem to have evolved as ISWs in the entire animal phylogeny, restricting the classification of ISW to traits that are only present or enlarged in adults of one of the sexes, and are used as weapons during intrasexual fights. Because of the absence of behavioural data and, in many cases, lack of sexually discriminated series from juveniles to adults, we exclude the fossil record from this review. We merge morphological, ontogenetic, and behavioural information, and for the first time thoroughly review the tree of life to identify separate evolution of ISWs. We found that ISWs are only found in bilateral animals, appearing independently in nematodes, various groups of arthropods, and vertebrates. Our review sets a reference point to explore other taxa that we identify with potential ISWs for which behavioural or morphological studies are warranted. We establish that most ISWs come in pairs, are located in or near the head, are endo- or exoskeletal modifications, are overdeveloped structures compared with those found in females, are modified feeding structures and/or locomotor appendages, are most common in terrestrial taxa, are frequently used to guard females, territories, or both, and are also used in signalling displays to deter rivals and/or attract females. We also found that most taxa lack ISWs, that females of only a few species possess better-developed weapons than males, that the cases of independent evolution of ISWs are not evenly distributed across the phylogeny, and that animals possessing the most developed ISWs have non-hunting habits (e.g. herbivores) or are faunivores that prey on very small prey relative to their body size (e.g. insectivores). Bringing together perspectives from studies on a variety of taxa, we conceptualize that there are five ways in which a sexually dimorphic trait, apart from the primary sex traits, can be fixed: sexual selection, fecundity selection, parental role division, differential niche occupation between the sexes, and interference competition. We discuss these trends and the factors involved in the evolution of intrasexually selected weaponry in nature.

Recent advances in understanding the mechanisms of sexually dimorphic plasticity: insights from beetle weapons and future directions

Many traits that are sexually dimorphic, appearing either differently or uniquely in one sex, are also sensitive to an organism's condition. This phenomenon seems to have evolved to limit genetic conflict between traits that are under different selective pressures in each sex. Recent work has shed light on the molecular and developmental mechanisms that govern this condition sensitive growth, and this work has now expanded to encompass both sexual dimorphism as well as conditionally plastic growth, as it seems the two phenomena are linked on a molecular level. In all cases studied the gene doublesex, a conserved regulator of sex differentiation, controls both sexual dimorphism as well as the condition-dependent plastic responses common to these traits. However, the advent of next-generation -omics technologies has allowed researchers to decipher the common and diverged mechanisms of sexually dimorphic plasticity and expand investigations beyond the foundation laid by studies utilizing beetle weapons.

Sexually dimorphic traits in the silkworm, Bombyx mori, are regulated by doublesex

The DM domain genes, doublesex (dsx) in insects, or their structural homologs, male abnormal 3 (mab-3) in nematodes and Dmrt1 (doublesex and mab-3-related transcription factor 1) in mammals, are downstream regulators of the sex determination pathway that control sexually dimorphic development. Despite the functional importance of dsx and its potential applications in sterile insect technologies (SITs), the mechanisms by which it controls sexually dimorphic traits and the subsequent developmental gene networks in insects are poorly understood. Phylogenetic analyses indicate that insect dsx genes have sex-specific alternative splicing isoforms, whereas other taxa do not. We exploited genome editing and transgenesis technologies to induce mutations in either the male-specific isoform (dsx^M) or common region (dsx^C) of dsx in the somatic tissues of the lepidopteran model insect Bombyx mori. Disruptions of gene function produced either male-specific sexually-dimorphic defects or intersexual phenotypes; these results differ from those observed in other insects, including Drosophila melanogaster. Our data provide insights into the divergence of the insect sex determination pathways related to the most conserved downstream component dsx.