Sex determination in the silkworm, Bombyx mori, is based on Feminizer (Fem), a W-linked Fem piRNA that triggers female development in WZ individuals, and the Z-linked Masculinizer (Masc), which ...initiates male development and dosage compensation in ZZ individuals. While Fem piRNA is missing in a close relative of B. mori, Masc determines sex in several representatives of distant lepidopteran lineages. We studied the molecular mechanisms of sex determination in the Mediterranean flour moth, Ephestia kuehniella (Pyralidae). We identified an E. kuehniella Masc ortholog, EkMasc, and its paralog resulting from a recent duplication, EkMascB. Both genes are located on the Z chromosome and encode a similar Masc protein that contains two conserved domains but has lost the conserved double zinc finger domain. We developed PCR-based genetic sexing and demonstrated a peak in the expression of EkMasc and EkMascB genes only in early male embryos. Simultaneous knock-down experiments of both EkMasc and EkMascB using RNAi during early embryogenesis led to a shift from male- to female-specific splicing of the E. kuehniella doublesex gene (Ekdsx), their downstream effector, in ZZ embryos and resulted in a strong female-biased sex-ratio. Our results thus confirmed the conserved role of EkMasc and/or EkMascB in masculinization. We suggest that the C-terminal proline-rich domain, we have identified in all functionally confirmed Masc proteins, in conjunction with the masculinizing domain, is important for transcriptional regulation of sex determination in Lepidoptera. The function of the Masc double zinc finger domain is still unknown, but appears to have been lost in E. kuehniella.
Various primary signals direct insect sex determination. In hymenopteran insects, the presence of a paternal genome is needed to initiate female development. When absent, uniparental haploid males ...develop. We molecularly and functionally identified the instructor sex-determination gene,
(
), of the haplodiploid wasp
This gene contains a P53-like domain coding region and arose by gene duplication and genomic rearrangements. Maternal silencing of
results in male development of haploid embryos. Upon fertilization, early zygotic transcription from the paternal
allele is initiated, followed by a timely zygotic expression of
(
), leading to female development.
is an instructor gene with a parent-of-origin effect in sex determination.
Insects exhibit a variety of sex determining mechanisms including male or female heterogamety and haplodiploidy. The primary signal that starts sex determination is processed by a cascade of genes ...ending with the conserved switch doublesex that controls sexual differentiation. Transformer is the doublesex splicing regulator and has been found in all examined insects, indicating its ancestral function as a sex-determining gene. Despite this conserved function, the variation in transformer nucleotide sequence, amino acid composition and protein structure can accommodate a multitude of upstream sex determining signals. Transformer regulation of doublesex and its taxonomic distribution indicate that the doublesex–transformer axis is conserved among all insects and that transformer is the key gene around which variation in sex determining mechanisms has evolved.
Animals develop sex-specific morphological structures that are diverse between organisms. However, understanding the developmental and evolutionary mechanisms governing these traits is still limited ...and largely restricted to DM domain genes, which are conserved, sex-specific developmental regulators identified in genetic models. Here, we report a sex-specific developmental regulator gene, glubschauge (glu) that selectively regulates sexually dimorphic eye differentiation in honeybees. We found that the sex determination gene feminizer (fem) controls sex-specific splicing of glu transcripts, establishing a genetic switch in which Glu proteins with a zinc finger (ZnF) domain are only expressed in females. We showed that female coding sequence was essential and sufficient for partial feminization. Comparative sequence and functional studies revealed that the evolutionary origination of the genetic switch was followed by the mutational origin of the essential ZnF domain. Our results demonstrate that glu is a newly evolved sex-specific genetic switch for region-specific regulation of a dimorphic character.
Pheromones are pivotal to sexual communication in insects. These chemical signals are processed by sexually dimorphic circuitries in the antennal lobe (AL) of the insect brain. However, there is ...limited understanding of how these circuitries form during AL development. Our review addresses this issue by comparing how circuitries develop throughout the growth processes of peripheral and deutocerebral neurons in various insect orders. Olfactory sensory neurons (OSNs) expressing novel pheromone receptors are eligible candidates to initiate new sexually‐dimorphic circuitries when these OSNs survive programmed cell death and match the physiological properties of pheromone‐sensing sensilla. The probability of these OSNs forming new glomeruli is largely determined by the degree of glia‐OSN interactions and projection neuron (PN) prepatterning. The relative contribution of either of these processes determines the degree of evolutionary neuroplasticity, which is particularly prevalent in those species with complex ALs lacking specific macroglomerular structures. The extent of sexual dimorphism is determined by sex‐determination genes, such as Doublesex and Fruitless, that regulate factors inducing OSN programmed cell death. Currently, these mechanisms are largely unexplored. This review, therefore, aims to provide a solid foundation for ongoing research into the evolution of AL sexual dimorphism and formation of pheromone circuitries in the light of insect sex determination.
Pheromones are pivotal to sexual communication. These chemical signals are processed by sexually dimorphic circuitries in the brain. This review compares how circuitries develop in the antennal lobe of various insect orders. Olfactory sensory neurons (OSNs) are eligible candidates to form new sexually dimorphic circuitries when surviving programmed cell death. The probability of OSNs forming new glomeruli is largely determined by the degree of glia‐OSN interactions and projection neuron prepatterning. The extent of sexual dimorphism is determined by sex‐determination genes.
Doublesex (Dsx) has a conserved function in controlling sexual morphological differences in insects, but our knowledge of its role in regulating sexual behaviour is primarily limited to
. Here, we ...show with the parasitoid wasp
that males whose
gene had been silenced (
-i) underwent a three-level pheromonal feminization: (i)
-i males were no longer able to attract females from a distance, owing to drastically reduced titres of the long-range sex pheromone; (ii)
-i males were courted by wild-type males as though they were females, which correlated with a lower abundance of alkenes in their cuticular hydrocarbon (CHC) profiles. Supplementation with realistic amounts of synthetic (
)-9-hentriacontene (
9C31), the most significantly reduced alkene in
-i males, to
-i males interrupted courtship by wild-type conspecific males. Supplementation of female CHC profiles with
9C31 reduced courtship and mating attempts by wild-type males. These results prove that
9C31 is crucial for sex discrimination in
; and (iii)
-i males were hampered in eliciting female receptivity and thus experienced severely reduced mating success, suggesting that they are unable to produce the to-date unidentified oral aphrodisiac pheromone reported in
males. We conclude that Dsx is a multi-level key regulator of pheromone-mediated sexual communication in
.
ABSTRACT
Biological control is widely successful at controlling pests, but effective biocontrol agents are now more difficult to import from countries of origin due to more restrictive international ...trade laws (the Nagoya Protocol). Coupled with increasing demand, the efficacy of existing and new biocontrol agents needs to be improved with genetic and genomic approaches. Although they have been underutilised in the past, application of genetic and genomic techniques is becoming more feasible from both technological and economic perspectives. We review current methods and provide a framework for using them. First, it is necessary to identify which biocontrol trait to select and in what direction. Next, the genes or markers linked to these traits need be determined, including how to implement this information into a selective breeding program. Choosing a trait can be assisted by modelling to account for the proper agro‐ecological context, and by knowing which traits have sufficiently high heritability values. We provide guidelines for designing genomic strategies in biocontrol programs, which depend on the organism, budget, and desired objective. Genomic approaches start with genome sequencing and assembly. We provide a guide for deciding the most successful sequencing strategy for biocontrol agents. Gene discovery involves quantitative trait loci analyses, transcriptomic and proteomic studies, and gene editing. Improving biocontrol practices includes marker‐assisted selection, genomic selection and microbiome manipulation of biocontrol agents, and monitoring for genetic variation during rearing and post‐release. We conclude by identifying the most promising applications of genetic and genomic methods to improve biological control efficacy.
All insects in the order Hymenoptera have haplodiploid sex determination, in which males emerge from haploid unfertilized eggs and females are diploid. Sex determination in the honeybee Apis ...mellifera is controlled by the complementary sex determination (csd) locus, but the mechanisms controlling sex determination in other Hymenoptera without csd are unknown. We identified the sex-determination system of the parasitic wasp Nasonia, which has no csd locus. Instead, maternal input of Nasonia vitripennis transformer (Nvtra) messenger RNA, in combination with specific zygotic Nvtra transcription, in which Nvtra autoregulates female-specific splicing, is essential for female development. Our data indicate that males develop as a result of maternal imprinting that prevents zygotic transcription of the maternally derived Nvtra allele in unfertilized eggs. Upon fertilization, zygotic Nvtra transcription is initiated, which autoregulates the female-specific transcript, leading to female development.
Sexually dimorphic traits in insects are subject to sexual selection, but our knowledge of the underlying molecular mechanisms is still scarce. Here we investigate how the highly conserved gene, ...Doublesex (Dsx), is involved in shaping sexual dimorphism in the model parasitoid wasp Nasonia vitripennis (Hymenoptera: Pteromalidae). First, we present the revised Dsx gene structure including an alternative transcription start, and two additional male NvDsx transcript isoforms. We show sex-specific NvDsx expression and splicing throughout development, and demonstrate that transient NvDsx silencing in different male developmental stages shifts two sexually dimorphic traits from male to female morphology, with the effect being dependent on the timing of silencing. In addition, we determined the effect of NvDsx on the development of reproductive organs. Transient silencing of NvDsx in early male larvae affects the growth and differentiation of the internal and external reproductive tissues. We did not observe phenotypic changes in females after NvDsx silencing. Our results indicate that male NvDsx is required to suppress female-specific traits and/or to promote male-specific traits during distinct developmental windows. This provides new insights into the regulatory activity of Dsx during male wasp development in the Hymenoptera.
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•Two novel male-specific Doublesex isoforms are identified in Nasonia vitripennis.•Doublesex suppresses the default development of female-specific morphological traits in N. vitripennis males.•Doublesex regulates the development of smaller wing size in N. vitripennis males during distinct developmental windows.•Doublesex regulates genitalia tissue growth and differentiation during larval development.
In recent years, our knowledge of the conserved master-switch gene doublesex (dsx) and its function in regulating the development of dimorphic traits in insects has deepened considerably. Here, a ...comprehensive overview is given on the properties of the male- and female-specific dsx transcripts yielding DSX(F) and DSX(M) proteins in Drosophila melanogaster, and the many downstream targets that they regulate. As insects have cell-autonomous sex determination, it was assumed that dsx would be expressed in every somatic cell, but recent research showed that dsx is expressed only when a cell is required to show its sexual identity through function or morphology. This spatiotemporal regulation of dsx expression has not only been established in D. melanogaster but in all insect species studied. Gradually, it has been appreciated that dsx could no longer be viewed as the master-switch gene orchestrating sexual development and behaviour in each cell, but instead should be viewed as the interpreter for the sexual identity of the cell, expressing this identity only on request, making dsx the central nexus of insect sex determination.
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