Vanden Broeck, J. | bioRxiv Science

bioRxiv2026

Infection with non-retroviral RNA viruses produces virus-derived DNA across diverse insect species

Growing evidence shows that eukaryotic genomes contain DNA sequences of non-retroviral RNA virus origin, yet the mechanisms underlying the generation of this virus-derived complementary DNA (vDNA) remain poorly understood, particularly in insects. Here, we demonstrate that infection with diverse non-retroviral RNA viruses induces the production of reverse-transcribed vDNA across multiple lepidopteran and hemipteran species. We further show that a Drosophila melanogaster-derived cell line actively secretes reverse-transcribed vDNA associated with extracellular vesicles (EVs), widely conserved nanoscale mediators of intercellular communication. Together, these findings reveal that infection-induced vDNA formation is a widespread phenomenon in insects and suggest that EVs may facilitate the systemic dissemination of vDNA.

biochemistry↗

bioRxiv2022

Multiplexed neuropeptide mapping in ant brains integrating microtomography and 3D mass spectrometry imaging

Neuropeptides are important regulators of animal physiology and behavior. Hitherto large-scale localization of neuropeptides mainly relied on immunohistochemical methods requiring the availability of antibody panels, while another limiting factor has been the brains opacity for subsequent light or fluorescence microscopy. To address these limitations, we integrated high-resolution mass spectrometry imaging (MSI) with microtomography for a multiplexed mapping of neuropeptides in two evolutionary distant ant species, Atta sexdens and Lasius niger. For analyzing the spatial distribution of chemically diverse peptide molecules across the brain in each species, the acquisition of serial mass spectrometry images was essential. As a result, we have comparatively mapped the 3D distributions of eight conserved neuropeptides throughout the brain micro-anatomy. We demonstrate that integrating the 3D MSI data into high-resolution anatomy models can be critical for studying organs with high plasticity such as brains of social insects. Several peptides, like the tachykinin-related peptides TK1 and TK4, were widely distributed in many brain areas of both ant species, whereas others, for instance myosuppressin was restricted to specific regions only. Also, we detected differences at the species level; many peptides were identified in the optic lobe of L. niger, but only one peptide (ITG-like) was found in this region in A. sexdens. Our approach provides the basis for investigating fundamental neurobiological processes by visualizing the unbiased 3D neurochemistry in its complex anatomic environment. Significance statementUntil recently, the inability to detect entire molecules such as neuropeptides within their spatial biological context and simultaneously link their occurrence to anatomically and physiologically relevant areas has limited our understanding of complex neurochemical processes. This situation has now changed dramatically with the optimization of a new multiplexed imaging method based on mass spectrometry, which enables us to study previously invisible processes at the microscopic scale. With the marriage of mass spectrometry imaging and microtomography, we show that it has become possible to build high-resolution maps of neuropeptides in complex anatomical structures as small as ant brains. These maps, embedded in the 3D neuroanatomy, expand the understanding of the spatial organization of brain chemistry and provide a baseline for neurobiological and neurochemical studies.

biophysics↗

bioRxiv2020

Crucial role of Juvenile Hormone receptor components Methoprene-tolerant and Taiman in sexual maturation of adult male desert locusts (Schistocerca gregaria)

The desert locust, Schistocerca gregaria, is an infamous migrating insect, generally considered to be one of the most dangerous pest species worldwide. In an area that encompasses one fifth of the Earths land surface, desert locust swarms can devastate the agricultural production. Consequently, they pose a serious threat to food security and can have a dramatic socio-economic impact. Currently (in 2020), large parts of East Africa, Southwest and South Asia are experiencing the worst desert locust plague in many decades. Exceptionally high rainfall in different regions has caused the favorable environmental conditions for very successful reproduction and population growth. To better understand the molecular mechanisms responsible for this remarkable reproductive capacity, as well as to fill existing knowledge gaps regarding the regulation of male reproductive physiology, we decided to investigate the role of the methoprene-tolerant (Scg-Met) and taiman (Scg-Tai) genes in adult male desert locusts. Methoprene-tolerant and Taiman belong to the basic helix-loop-helix/Per-Arnt-Sim (bHLH/PAS) family of transcription factors and form a complex that is responsible for transducing the Juvenile Hormone (JH) signal. So far, in vivo research has mainly focused on the role of these JH receptor components in post-embryonic development, as well as in the reproductive physiology of adult female insects. In the current study, we show that silencing these components by RNA interference strongly inhibits sexual maturation of gregarious desert locust males, thereby severely disrupting reproduction. This observation is evidenced by the absence of a yellow colored cuticle, the significant reduction in the relative weight of the testes, the inability to show mating behavior, and the drastically reduced phenylacetonitrile (PAN) pheromone levels of the treated males. In addition, we also observed significant reductions of the relative weight, as well as the relative protein content, of the male accessory glands in Scg-Met knockdown locusts. Interestingly, in these animals the size of the corpora allata (CA), the endocrine glands where JH is synthesized, was significantly increased, and a significant rise was observed in the relative transcript levels of JH acid methyltransferase (JHAMT), a rate-limiting enzyme in the JH biosynthesis pathway. Moreover, other endocrine pathways also appeared to be affected by the knockdown, as evidenced by significant changes in the levels of the transcripts coding for the insulin-related peptide and for two neuroparsins in the fat body. Our results demonstrate that JH signaling pathway components play a crucial role in male reproductive physiology. Since they are crucial for a successful reproduction, they may hold great potential as candidate targets for the design of novel strategies for locust population management. Significance statementDesert locusts can form devastating swarms that threaten the livelihood in many of the worlds poorest countries, as demonstrated by the plagues in East Africa, Southwest and South Asia that are currently covered in the news worldwide. Control of this migratory pest mainly relies on the large-scale use of neurotoxic insecticides, also affecting non-target organisms in their already fragile habitats. Therefore, the identification of novel molecular targets for the design of more sustainable and more selective pest management techniques remains of crucial importance. Potential candidate targets in this respect are pathway components that transduce signals of typical insect hormones, such as ecdysteroids and juvenile hormones. By focusing in our current study on the JH receptor components, we showed that the reproductive capacities of desert locust males can be severely inhibited in an early stage, resulting in individuals that display no mating behavior, do not produce an important pheromone and do not show the characteristic yellow color of sexually mature gregarious males. Specifically targeting molecular components of the JH signaling pathway in future, more biorational control strategies could therefore be a very successful way by which expansion of these devastating plagues might be prevented.

molecular biology↗