Jozef Vanden Broeck | KU Leuven (original) (raw)

Papers by Jozef Vanden Broeck

Scientific Reports, 2019

Juvenile hormones (JH) are key endocrine regulators produced by the corpora allata (CA) of insect... more Juvenile hormones (JH) are key endocrine regulators produced by the corpora allata (CA) of insects. Together with ecdysteroids, as well as nutritional cues, JH coordinates different aspects of insect postembryonic development and reproduction. The function of the recently characterized JH receptor, Methoprene-tolerant (Met), appears to be conserved in different processes regulated by JH. However, its functional interactions with other hormonal signalling pathways seem highly dependent on the feeding habits and on the developmental and reproductive strategies employed by the insect species investigated. Here we report on the effects of RNA interference (RNAi) mediated SgMet knockdown during the first gonadotrophic cycle in female desert locusts (Schistocerca gregaria). This voracious, phytophagous pest species can form migrating swarms that devastate field crops and harvests in several of the world’s poorest countries. A better knowledge of the JH signalling pathway may contribute to...

Journal of Insect Physiology, 2019

Next generation sequencing has revealed the widespread occurrence of persistent virus infections ... more Next generation sequencing has revealed the widespread occurrence of persistent virus infections in insects but little is known regarding to what extent persistent infections can affect cellular physiology and how they might contribute to the development of disease. In contrast to the pathogenic infections occurring in Drosophila S2 cells, it was observed that Cricket Paralysis virus (CrPV; Dicistroviridae) causes persistent infections in 9 lepidopteran and 2 coleopteran cell lines. The status of the persistent infection was subsequently investigated in more detail using silkworm-derived Bm5 cells, where the infection eventually becomes pathogenic after 3-4 weeks. The short-term persistence period in Bm5 cells is characterized by low levels of viral replication and virion production as well as by the production of viral siRNAs. However, during this period cellular physiology also becomes altered since the cells become susceptible to infection by the nodavirus Flock House virus (FHV). Pathogenicity and widespread mortality at 4 weeks is preceded by a large increase in virion production and the transcriptional activation of immune-related genes encoding RNAi factors and transcription factors in the Toll, Imd and Jak-STAT pathways. During the infection of Bm5 cells, the infective properties of CrPV are not altered, indicating changes in the physiology of the host cells during the transition from short-term persistence to pathogenicity. The in vitro system of Bm5 cells persistently infected with CrPV can therefore be presented as an easily accessible model to study the nature of persistent virus infections and the processes that trigger the transition to pathogenicity, for instance through the application of different "omics" approaches (transcriptomics, proteomics, metabolomics). The different factors that can cause the transition from persistence to pathogenicity in the Bm5-CrPV infection model are discussed.

Scientific Reports, 2018

While regulatory RNA pathways, such as RNAi, have commonly been described at an intracellular lev... more While regulatory RNA pathways, such as RNAi, have commonly been described at an intracellular level, studies investigating extracellular RNA species in insects are lacking. In the present study, we demonstrate the presence of extracellular microRNAs (miRNAs) in the cell-free conditioned media of two Drosophila cell lines. More specifically, by means of quantitative real-time PCR (qRT-PCR), we analysed the presence of twelve miRNAs in extracellular vesicles (EVs) and in extracellular Argonaute-1 containing immunoprecipitates, obtained from the cell-free conditioned media of S2 and Cl.8 cell cultures. Next-generation RNA-sequencing data confirmed our qRT-PCR results and provided evidence for selective miRNA secretion in EVs. To our knowledge, this is the first time that miRNAs have been identified in the extracellular medium of cultured cells derived from insects, the most speciose group of animals.

Scientific Reports, 2017

Venus kinase receptors (VKR) are a subfamily of invertebrate receptor tyrosine kinases, which hav... more Venus kinase receptors (VKR) are a subfamily of invertebrate receptor tyrosine kinases, which have only recently been discovered. They contain an intracellular tyrosine kinase domain and an extracellular Venus FlyTrap domain. VKRs have been functionally and pharmacologically characterized in only two invertebrate species, namely the human parasite Schistosoma mansoni and the mosquito Aedes aegypti, where they play a crucial role in oogenesis. Here, we report the characterization of a VKR in the desert locust, Schistocerca gregaria. We performed an in-depth profiling study of the SgVKR transcript levels in different tissues throughout the female adult stage. Using the RNA interference technique, the possible role of SgVKR was investigated. SgVKR knockdown had significant effects on ovarian ecdysteroid levels and on the size of oocytes during the vitellogenic stage. SgVKR is probably involved in the complex cross-talk between several important pathways regulating female reproductive physiology. Contrary to A. aegypti and S. mansoni, we cannot conclude that this receptor is essential for reproduction, since silencing SgVKR did not affect fecundity or fertility. Considering the evolutionary distance between A. aegypti and S. gregaria, as well as the differences in regulation of their female reproductive physiology, this article constitutes a valuable asset in better understanding VKRs. In 2003, a novel receptor tyrosine kinase (RTK) was discovered in the human parasite, Schistosoma mansoni 1. This membrane receptor was designated as the venus kinase receptor (VKR), since it possesses an extracellular ligand-binding Venus FlyTrap (VFT) domain that is connected via a single membrane spanning segment with the intracellular tyrosine kinase (TK) domain. VKR-encoding genes have since then been identified in genomes of several other invertebrate species 2. In most of these species, only one vkr gene was found, but the genomes of some Trematoda, such as Schistosoma 3 , and Lepidoptera contain two vkr genes (vkr1 and vkr2). It should also be noted that no vkr genes were found in two major invertebrate research models, Drosophila melanogaster and Caenorhabditis elegans. Phylogenetic analysis evinced that all putative VKRs are clustering as a monophyletic group and likely evolved from a common ancestor 2. The TK domain of VKR closely resembles that of insulin-like peptide receptors (InR) and contains all motifs that are crucial for tyrosine kinase activity, such as the ATP binding site (GxGxxG), the catalytic loop implicated in the phosphotransfer (HRDxAxRN), and the two putative autophosphorylation sites (YY) 4. Using recombinant VKRs and in vitro kinase assays, it was demonstrated that VKRs are functional tyrosine kinase receptors that can form dimers and autophosphorylate 4,5. Phylogenetic and structural analysis of the VFT module (VFTM) of VKRs and other VFTM-containing receptors resulted in the identification of a monophyletic VKR clade which is closely resembling the γ-aminobutyric acid type B receptors (GABA B R) 4. VFTMs of class C G protein-coupled receptors (GPCRs), including GABA B R, bind small ligands such as Ca 2+ , GABA and other amino acid transmitters, and small sugars 6. Class C GPCRs that bind amino acids contain a consensus motif of 8 residues in their VFTM, which can be found in most VKRs 2. In vitro kinase assays have shown that the VKR of Apis mellifera and SmVKR1 are activated by L-Arg, while SmVKR2 is activated by Ca 2+ 3,4. Moreover, for the amino acid recognition by VKRs the serine and arginine residues of the conserved 8 residue motif are required 2. Very recently, the VKR of Aedes aegypti was also deorphanized and surprisingly AaVKR was shown to bind to the rather 'large' ovary

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Desert locusts (Schistocerca gregaria) and migratory locusts (Locusta migratoria) are closely rel... more Desert locusts (Schistocerca gregaria) and migratory locusts (Locusta migratoria) are closely related species, which display a fascinating type of phenotypic plasticity called phase transition. This means that these locusts can occur in two extreme phenotypes: the ...

Neurotransmitter, 2015

Serotonin is an ancient monoamine neurotransmitter, biochemically derived from tryptophan. It is ... more Serotonin is an ancient monoamine neurotransmitter, biochemically derived from tryptophan. It is most abundant in the gastrointestinal tract, but is also present throughout the rest of the body of animals and can even be found in plants and fungi. Serotonin is especially famous for its contributions to feelings of well-being and happiness. More specifically it is involved in learning and memory processes and is hence crucial for certain behaviors throughout the animal kingdom. This brief review will focus on the metabolism, biological role and mode-of-action of serotonin in insects. First, some general aspects of biosynthesis and breakdown of serotonin in insects will be discussed, followed by an overview of the functions of serotonin, serotonin receptors and their pharmacology. Throughout this review comparisons are made with the vertebrate serotonergic system. Last but not least, possible applications of pharmacological adjustments of serotonin signaling in insects are discussed.

Foods

Edible orthopterans (grasshoppers, crickets, and locusts) are major delicacies, especially across... more Edible orthopterans (grasshoppers, crickets, and locusts) are major delicacies, especially across sub-Saharan Africa. Their promotion as food ingredients is increasingly gaining momentum. This study evaluates the nutritional profiles of three widely consumed orthopterans: Gryllus bimaculatus, Locusta migratoria, and Schistocerca gregaria after blanching and oven-drying. All three species had high protein (65.3, 54.2, and 61.4% on a dry matter (DM) basis for G. bimaculatus, L. migratoria, and S. gregaria, respectively) and fat contents. Oleic (22.9–40.8%) and palmitic (26.1–43.0%) were the two most abundant fatty acids. All essential amino acids (in mg/100 g protein) were present, with glutamic acid (120–131), alanine (90.2–123), and leucine (82.3–84.6) being the most abundant. The minerals (in mg/100 g dry matter) potassium (796–1309) and phosphorus (697–968) were moderately high, and iron (4.60–7.31), zinc (12.7–24.9), manganese (0.40–7.15), and copper (1.20–4.86) were also observe...

Ecdysteroid levels were determined for hemolymph samples (A) and ovary samples (B). Anim... more Ecdysteroid levels were determined for hemolymph samples (A) and ovary samples (B). Animals were injected with 4 µg OMP-DH dsRNA or 4 µg GFP dsRNA on day 5. Hemolymph samples were taken on several time points until day 12. Samples were extracted and measured with the EIA. The resulting average ecdysteroid titers for the different time points are represented in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0031425#pone-0031425-g007" target="_blank">Figure 7A</a>. On day 12, ovaries were dissected, ecdysteroids were extracted and measured with the enzyme immunoassay before (free ecdysteroids) and after enzyme treatment (“total” ecdysteroids). The resulting ecdysteroid content per mg tissue is represented in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0031425#pone-0031425-g007" target="_blank">Figure 7B</a>. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0031425#s3" target="_blank">Results</a> were obtained by analyzing about 25 individuals per condition and are represented as means ± S.D. Asterisks indicate significant differences (P<0.01) between the experimental and control groups (unpaired t-test).</p

Transcript levels were determined on day 4 and day 10 of the adult stage in males (A) an... more Transcript levels were determined on day 4 and day 10 of the adult stage in males (A) and females (B). <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0031425#s3" target="_blank">Results</a> were obtained by analyzing three independent pools of eight individuals per condition and are represented as means ± S.D. Normalization was performed according to Vandesompele et al. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0031425#pone.0031425-Vandesompele1" target="_blank">[26]</a>, using the geNorm applet. Abbreviations used on the X-axis: Br: brain, Opl: optic lobes, Sog: suboesophageal ganglion, T1: prothoracic ganglion, T2: mesothoracic ganglion, T3: metathoracic ganglion, Ab 4–5: abdominal ganglia 4 and 5, Ab 6–7: Abdominal ganglia 6 and 7, Ab 8: Abdominal ganglion 8.</p

Animals were injected daily with 1 pmol CRF-like DH (dissolved in 4 µl Milli-Q® water) s... more Animals were injected daily with 1 pmol CRF-like DH (dissolved in 4 µl Milli-Q® water) starting from day 1 until day 15 of the adult stage. Control animals were injected in the same way, but only with Milli-Q® water. The resulting average oocyte size (measured on day 15) is represented on the Y-axis. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0031425#s3" target="_blank">Results</a> were obtained by analyzing more than 25 individuals per condition and are represented as means ± S.D. Asterisks indicate significant differences (P<0.01) between the experimental group and the control group (unpaired t-test).</p

Ecdysteroid levels were determined for hemolymph samples (A) and ovary samples (B). Anim... more Ecdysteroid levels were determined for hemolymph samples (A) and ovary samples (B). Animals were injected daily with 1 pmol CRF-like DH (dissolved in 4 µl Milli-Q® water) from day 1 until day 15 of the adult stage. Control animals were injected in the same way, but only with Milli-Q® water. Hemolymph samples were taken on different time points and the ecdysteroid content was measured with the EIA. The resulting average ecdysteroid titers for the different time points are represented in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0031425#pone-0031425-g005" target="_blank">figure 5A</a>. On day 15, ovaries were dissected, ecdysteroids were extracted and measured with the enzyme immunoassay before (free ecdysteroids) and after enzyme treatment (“total” ecdysteroids). The resulting ecdysteroid content per mg tissue is represented in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0031425#pone-0031425-g005" target="_blank">Figure 5B</a>. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0031425#s3" target="_blank">Results</a> were obtained by analyzing more than 25 individuals per condition and are represented as means ± S.D. Asterisks indicate significant differences (P<0.01) between the different experimental groups and control groups (unpaired t-test).</p

Viruses

Insect antiviral immunity primarily relies on RNAi mechanisms. While a key role of small interfer... more Insect antiviral immunity primarily relies on RNAi mechanisms. While a key role of small interfering (si)RNAs and AGO proteins has been well established in this regard, the situation for PIWI proteins and PIWI-interacting (pi)RNAs is not as clear. In the present study, we investigate whether PIWI proteins and viral piRNAs are involved in the immunity against single-stranded RNA viruses in lepidopteran cells, where two PIWIs are identified (Siwi and Ago3). Via loss- and gain-of-function studies in Bombyx mori BmN4 cells and in Trichoplusia ni High Five cells, we demonstrated an antiviral role of Siwi and Ago3. However, small RNA analysis suggests that viral piRNAs can be absent in these lepidopteran cells. Together with the current literature, our results support a functional diversification of PIWI proteins in insects.

A) Multiple sequence alignment of the long S. gregaria OMP-DH precurs... more A) Multiple sequence alignment of the long S. gregaria OMP-DH precursor and several homologous insect precursors, performed with use of the ClustalW program (<a href="http://www.ebi.ac.uk/clustalw/" target="_blank">http://www.ebi.ac.uk/clustalw/</a>), available from the European Bioinformatics Institute. Default parameters were used. The consensus is presented under each part of the alignment as follows: ‘*’ represents a position at which an amino acid is completely conserved, while ‘:’ and ‘.’ represent positions with lower degrees of conservation. The dashed boxes indicate the OMP-encoding region of the S. gregaria precursor (the region between the signal peptide and the first cleavage site of the S. gregaria precursor) and the corresponding region of the other precursors. The full boxes indicate the CRF-like DH coding region, flanked by dibasic cleavage sites (“(G)KR”). Abbreviations: Apime-DHP, Apis mellifera CRF-like DH precursor <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0031425#pone.0031425-Hummon1" target="_blank">[16]</a>; Harsa-DHP, Harpegnathos saltator CRF-like DH precursor (UniProtKB/TrEMBL: E2B7W2); Schgr-DHP, S. gregaria OMP-DH-L precursor (described in this paper); Rhopr-DHP, Rhodnius prolixus CRF-like DH precursor <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0031425#pone.0031425-TeBrugge1" target="_blank">[5]</a>, UniProtKB/TrEMBL: F1AYR6; Trica-DHP, Tribolium castaneum CRF-like DH (47) precursor <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0031425#pone.0031425-Li1" target="_blank">[17]</a>. B) Alignment of the CRF-like peptides and OMPs from Schistocerca gregaria (Schgr-DH and Schgr-OMP) and Locusta migratoria (Locmi-CRF/DH and Locmi-OMP). Both CRF-like peptides are C-terminally amidated (“a”). Abbreviations: Locmi-CRF/DH, CRF-like DH from L. migratoria <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0031425#pone.0031425-Kay1" target="_blank">[6]</a>–<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0031425#pone.0031425-Lehmberg1" target="_blank">[7]</a>, UniProtKB/TrEMBL: P23465); Schgr-DH, CRF-like DH from S. gregaria (this paper); Locmi-OMP, Ovary Maturating Parsin from L. migratoria <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0031425#pone.0031425-Girardie1" target="_blank">[19]</a>, UniProtKB/TrEMBL: P80045; Schgr-OMP: the longest Ovary Maturating Parsin isoform from S. gregaria <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0031425#pone.0031425-Girardie4" target="_blank">[22]</a>.</p

International Journal of Molecular Sciences, 2021

Accurate control of innate behaviors associated with developmental transitions requires functiona... more Accurate control of innate behaviors associated with developmental transitions requires functional integration of hormonal and neural signals. Insect molting is regulated by a set of neuropeptides, which trigger periodic pulses in ecdysteroid hormone titers and coordinate shedding of the old cuticle during ecdysis. In the current study, we demonstrate that crustacean cardioactive peptide (CCAP), a structurally conserved neuropeptide described to induce the ecdysis motor program, also exhibits a previously unknown prothoracicostatic activity to regulate ecdysteroid production in the desert locust, Schistocerca gregaria. We identified the locust genes encoding the CCAP precursor and three G protein-coupled receptors that are activated by CCAP with EC50 values in the (sub)nanomolar range. Spatiotemporal expression profiles of the receptors revealed expression in the prothoracic glands, the endocrine organs where ecdysteroidogenesis occurs. RNAi-mediated knockdown of CCAP precursor or r...

Plants, 2021

RNA-mediated pathways form an important regulatory layer of myriad biological processes. In the l... more RNA-mediated pathways form an important regulatory layer of myriad biological processes. In the last decade, the potential of RNA molecules to contribute to the control of agricultural pests has not been disregarded, specifically via the RNA interference (RNAi) mechanism. In fact, several proofs-of-concept have been made in this scope. Furthermore, a novel research field regarding extracellular RNAs and RNA-based intercellular/interorganismal communication is booming. In this article, we review key discoveries concerning extracellular RNAs in insects, insect RNA-based cell-to-cell communication, and plant–insect transfer of RNA. In addition, we overview the molecular mechanisms implicated in this form of communication and discuss future biotechnological prospects, namely from the insect pest-control perspective.

Scientific Reports, 2019

Journal of Insect Physiology, 2019

Scientific Reports, 2018

Scientific Reports, 2017

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KULeuven. ...

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Neurotransmitter, 2015

Foods

Ecdysteroid levels were determined for hemolymph samples (A) and ovary samples (B). Anim... more Ecdysteroid levels were determined for hemolymph samples (A) and ovary samples (B). Animals were injected daily with 1 pmol CRF-like DH (dissolved in 4 µl Milli-Q® water) from day 1 until day 15 of the adult stage. Control animals were injected in the same way, but only with Milli-Q® water. Hemolymph samples were taken on different time points and the ecdysteroid content was measured with the EIA. The resulting average ecdysteroid titers for the different time points are represented in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0031425#pone-0031425-g005" target="_blank">figure 5A</a>. On day 15, ovaries were dissected, ecdysteroids were extracted and measured with the enzyme immunoassay before (free ecdysteroids) and after enzyme treatment (“total” ecdysteroids). The resulting ecdysteroid content per mg tissue is represented in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0031425#pone-0031425-g005" target="_blank">Figure 5B</a>. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0031425#s3" target="_blank">Results</a> were obtained by analyzing more than 25 individuals per condition and are represented as means ± S.D. Asterisks indicate significant differences (P<0.01) between the different experimental groups and control groups (unpaired t-test).</p

Viruses

International Journal of Molecular Sciences, 2021

Plants, 2021