Eveline C. Verhulst

Wageningen University & Research | WUR · Department of Entomology

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 a...

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 al...

Although sex determination is a universal process in sexually reproducing organisms, sex determination pathways are among the most highly variable genetic systems found in nature. Nevertheless, general principles can be identified among the diversity, like the central role of transformer (tra) in insects. When a functional TRA protein is produced i...

Paternal factor specifies female wasps Not all animals have specialized sex chromosomes to determine their sex. In hymenopteran insects, for example, unfertilized eggs become males and fertilized eggs become females. Prior work showed that the paternal genome provides instruction for female development. Zou et al. identified a sex determination ins...

Populations of the green peach aphid, Myzus persicae, rapidly develop resistance to insecticides applied in agriculture, necessitating regular resistance monitoring of pest populations. Previous research identified two dominant multilocus genotypes (MLGs) in conventional (using insecticides + biological control agents) Dutch sweet pepper greenhouse...

Whole‐genome duplication (polyploidy) poses many complications but is an important driver for eukaryotic evolution. To experimentally study how many challenges from the cellular (including gene expression) to the life history levels are overcome in polyploid evolution, a system in which polyploidy can be reliably induced and sustained over generati...

Aphids display remarkable adaptability to pest control strategies and their parthenogenetic reproduction results in rapid numerical increase of higher-fitness clones. Consequently, a high prevalence of only a few clonal lines could indicate positive selection for these genotypes, potentially reflecting adaptation to pest control methods. Here, we i...

Background The primary signals of sex determination in insects are diverse and evolve erratically. This also appears to be the case with moths and butterflies. In the silkworm Bombyx mori, female development is triggered by a W-linked Feminizer (Fem) piRNA by degrading the mRNA of the Z-linked Masculinizer (Masc) gene, which controls male developme...

The occurrence of facultative endosymbionts has been studied in many commercially important crop pest aphids, but their occurrence and effects in non‐commercial aphid species in natural populations have received less attention. We screened 437 aphid samples belonging to 106 aphid species for the eight most common facultative aphid endosymbionts. We...

Aphids are major agricultural pests and laboratory studies have shown that heritable bacterial endosymbionts can protect aphids against biocontrol parasitoids, but results from agricultural crop systems are lacking. Here we assess (1) which aphid species are present in Dutch strawberry crops, (2) which facultative endosymbionts they carry, and (3)...

Endosymbionts are maternally transmitted, and therefore benefit from maximizing female offspring numbers. Parthenogenesis-induction (PI) is the most effective type of manipulation for transmission, but has solely been detected in haplodiploid species, whereas cytoplasmic incompatibility (CI) is detected frequently across the arthropod phylum, inclu...

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 s...

Wolbachia manipulates host reproduction in various haplodiploid insect species, in which fertilized eggs normally develop into diploid females while unfertilized eggs develop into haploid males. Females infected with a thelytoky-inducing Wolbachia produce diploid daughters from unfertilized eggs (thelytoky), but in some infected species diploid mal...

Biological control (biocontrol) of crop pests is a sustainable alternative to the use of biodiversity and organismal health harming chemical pesticides. Aphids can be biologically controlled with parasitoid wasps, however, variable results of parasitoid‐based aphid biocontrol in greenhouses are reported. Aphids may display genetically encoded (endo...

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 t...

p>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 throughou...

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 Drosophila. Here, we show with the parasitoid wasp Nasonia vitripennis that males whose Dsx gene had been silenced (NvDsx-i) underwent a three-level pheromonal femi...

The parasitoid wasp Muscidifurax raptorellus (Hymenoptera: Pteromalidae) is a gregarious species that has received extensive attention for its potential in biological pest control against house fly, stable fly, and other filth flies. It has a high reproductive capacity and can be reared easily. However, genome assembly is not available for M. rapto...

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 seve...

The transcription factor Doublesex (Dsx) has a conserved function in controlling sexual morphological differences in insects, but our knowledge on its role in regulating sexual behavior is widely limited to Drosophila. Here, we show in the parasitoid wasp Nasonia vitripennis that males whose Dsx gene had been silenced by RNA interference (NvDsx-i)...

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 i...

RNA interference (RNAi) is a technique used in many insects to study gene function. However, prior research suggests possible off-target effects when using Green Fluorescent Protein (GFP) sequence as a non-target control. We used a transcriptomic approach to study the effect of GFP RNAi (GFP-i) in Nasonia vitripennis, a widely used parasitoid wasp...

Nesidiocoris tenuis (Reuter) is an efficient predatory biological control agent used throughout the Mediterranean Basin in tomato crops but regarded as a pest in northern European countries. From the family Miridae, it is an economically important insect yet very little is known in terms of genetic information and no genomic or transcriptomic studi...

Bracon brevicornis is an ectoparasitoid of a wide range of larval-stage Lepidopterans, including several pests of important crops, such as the corn borer, Ostrinia nubilalis. It is also one of the earliest documented cases of complementary sex determination in Hymenoptera. Here, we present the linked-read-based genome of B. brevicornis, complete wi...

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 genom...

Trichogramma brassicae (Bezdenko) are egg parasitoids that are used throughout the world as biological control agents and in laboratories as model species. Despite this ubiquity, few genetic resources exist beyond COI, ITS2, and RAPD markers. Aided by a Wolbachia infection, a wild-caught strain from Germany was reared for low heterozygosity and seq...

Bracon brevicornis is an ectoparasitoid of a wide range of larval-stage Lepidopterans, including several pests of important crops, such as the corn borer, Ostrinia nubilalis. It is also one of the earliest documented cases of complementary sex determination in Hymenoptera. Here, we present the linked-read genome of B. brevicornis, complete with an...

Bracon brevicornis is an ectoparasitoid of a wide range of larval-stage Lepidopterans, including several pests of important crops, such as the corn borer, Ostrinia nubilalis . It is also one of the earliest documented cases of complementary sex determination in Hymenoptera. Here, we present the linked-read genome of B. brevicornis , complete with a...

Sexually dimorphic traits in insects are rapidly evolving due to sexual selection which can ultimately lead to speciation. However, our knowledge of the underlying sex-specific molecular mechanisms is still scarce. Here we show that the highly conserved gene, Doublesex (Dsx), regulates rapidly diverging sexually dimorphic traits in the model parasi...

Trichogramma brassicae (Bezdenko) are egg parasitoids that are used throughout the world as biological control agents and in laboratories as model species. Despite this ubiquity, few genetic resources exist beyond COI, ITS2, and RAPD markers. Aided by a Wolbachia infection, a wild-caught strain from Germany was reared for low heterozygosity and seq...

Nesidiocoris tenuis (Reuter) is an efficient predatory biological control agent used throughout the Mediterranean Basin in tomato crops but regarded as a pest in northern European countries. Belonging to the family Miridae, it is an economically important insect yet very little is known in terms of genetic information: no published genome, populati...

Biological control is widely successful for controlling pests, but effective biocontrol agents are now more difficult to obtain due to more restrictive international trade laws. 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 underut...

Amblyseius swirskii Athias‐Henriot (Acari: Phytoseiidae) is a predatory mite used to control whiteflies and thrips in protected crops. This biocontrol agent, originating from the Eastern Mediterranean region, has been mass‐reared for commercial use since 2005 and is widely used in augmentative biocontrol programs. As a polyphagous predator, it has...

Poster presented at Entomologendag 2017 in The Netherlands. Made in the style of a choose your own adventure guide, based on a dichotomous key of sequencing approaches. No original data present, but based on our work so far in sequencing the genomes of different biocontrol agents. CC by 4.0 Abstract: The desire for sequencing non-model insect genom...

This is a presentation given the the 5th International Entomophagous Insect Conference in Kyoto, Japan, on October 18th, 2017. Abstract: Innovations within the realm of genetic sequencing have led to increased accessibility for biologists, both in terms of costs as well as the educational resources available, regardless of background. Our project i...

In many insect species maternal provision of sex-specifically spliced messenger RNA (mRNA) of sex determination genes is an essential component of the sex determination mechanism. In haplodiploid Hymenoptera, maternal provision in combination with genomic imprinting has been shown for the parasitoid Nasonia vitripennis, known as maternal effect gen...

In insect sex determination a primary signal starts the genetic sex determination cascade that, in most insect orders, is subsequently transduced down the cascade by a transformer (tra) ortholog. Only a female-specifically spliced tra mRNA yields a functional TRA-protein that forms a complex with TRA2, encoded by a transformer-2 (tra2) ortholog, to...

Abstract: Biocontrol is the introduction of one organism to control the population of another organism, and has had a commercial application for over a century. With the latest advances in next generation sequencing, now is the moment to both improve biocontrol as well as counter potential shortcomings, such as non-target effects. For example, when...

Personality traits are heritable and respond to natural selection, but are at the same time influenced by the ontogenetic environment. Epigenetic effects, such as DNA methylation, have been proposed as a key mechanism to control personality variation. However, to date little is known about the contribution of epigenetic effects to natural variation...

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 melan...

The research into the Drosophila melanogaster sex-determining system has been at the basis of all further research on insect sex determination. This further research has made it clear that, for most insect species, the presence of sufficient functional Transformer (TRA) protein in the early embryonic stage is essential for female sexual development...

Genetic model organisms have gifted researchers with a breathtakingly detailed understanding of the most intimate aspects of their genomes, cells, and development. And yet there is a problem—model organisms have been selected because they have simple life histories and happily inhabit laboratories. In short, they make a virtue of being boring. But...

Although the role of DNA methylation in insect development is still poorly understood, the number and role of DNA methyltransferases in insects vary strongly between species. DNA methylation appears to be widely present among the social hymenoptera and functional studies in Apis have suggested a crucial role for de novo methylation in a wide variet...

We report here genome sequences and comparative analyses of three closely related parasitoid wasps: Nasonia vitripennis, N. giraulti, and N. longicornis. Parasitoids are important regulators of arthropod populations, including major agricultural pests and disease vectors, and Nasonia is an emerging genetic model, particularly for evolutionary and d...

Primers used to genotype recombinants in the ws1 region. Base pair position in N. vitripennis genome assembly v1.0 SCAFFOLD23 is shown. Dashed line denotes markers within the mapped 13.5kb/10.8kb ws1 region. PCR conditions for all markers: 94C for 2min, 34 cycles of (94C for 30s, 55C for 45s, 72C for 60s), 72C for 10min. Enzyme: Restriction enzyme...

Wing setae are used to estimate changes in cell size. Example images of seta and nuclear density from male pupal and adult forewings are shown. Adult wing seta numbers and densities were used to infer changes in cell number and cell size due to ws1 (Table 2), based on estimates of the number of cells (nuclei) per seta in the pupal wing (Data presen...

Locations of dsx primers. Primer locations used for RT–PCR and qPCR of dsx are shown in relation to the dsx gene model. Male and female splice-forms are adapted from [18]. Lengths are not to scale. Approximate primer locations (half-arrows) are shown on the male splice-form for (a) male-specific dsxM qPCR, (b) non-sex-specific dsx qPCR, and (c) dsx...

Dsx splicing in male prepupal wings.RT–PCR of the differentially spliced 3’ domain of dsx in prepupal male wings is shown. RNA from single male prepupal wings, single male prepupal legs, and single whole pupal females was isolated using the Dynabeads mRNA DIRECT Micro Kit (Invitrogen) by the mini volumes protocol. Black arrowhead: 573bp unspliced (...

We report here genome sequences and comparative analyses of three closely related parasitoid wasps: Nasonia vitripennis, N. giraulti, and N. longicornis. Parasitoids are important regulators of arthropod populations, including major agricultural pests and disease vectors, and Nasonia is an emerging genetic model, particularly for evolutionary and d...

The genetic basis of morphological differences among species is still poorly understood. We investigated the genetic basis of sex-specific differences in wing size between two closely related species of Nasonia by positional cloning a major male-specific locus, wing-size1 (ws1). Male wing size increases by 45% through cell size and cell number chan...

The doublesex (dsx) gene of the parasitic wasp Nasonia vitripennis is described and characterized. Differential splicing of dsx transcripts has been shown to induce somatic sexual differentiation in Diptera and Lepidoptera, but not yet in other insect orders. Two spliceforms of Nasonia dsx mRNA are differentially expressed in males and females. In...

In the research of Eveline Verhulst the involvement of epigenetic modification in sex determination is shown for the first time. Both humans and the fruitfly Drosophila reproduce sexually, so their offspring has genes from both father and mother. The parasitic wasp Nasonia also reproduces sexually but females can produce offspring without mating. T...