Biology subjects

Duplais, C.

Publications and source records attributed to Duplais, C..

5 recordsLinked to original sources

bioRxiv2026

optix regulates abdominal melanin pigmentation in the tobacco hawkmoth Manduca sexta

Research on butterflies has uncovered a conserved "toolkit" of genes for color pattern development and evolution. One of these genes is optix, a homeobox transcription factor that regulates ommochrome and melanin pigmentation, as well as structural coloration, in nymphalid butterflies. It remains unclear, however, whether optix plays any roles in color patterning outside of the Nymphalidae. We used CRISPR-Cas9 to disrupt optix in the tobacco hornwormmoth Manduca sexta and observed a dramatic abdominal pigmentation phenotype, where orange pigmentation was replaced by black eumelanin. Chemical assays suggest that the orange pigment is not an ommochrome, indicating that optix modulates an alternative, uncharacterized pigment pathway in M. sexta. RNA-seq and chemical analyses of orange and black abdominal scales lead us to speculate that the orange pigment may be a type of melanin, perhaps N-{beta}-alanyldopamine (NBAD) sclerotin. Our results suggest that optix plays a deeply ancestral role in pigment regulation in Lepidoptera, and demonstrates evolutionary flexibility in how it interfaces with pigment chemistry across moths and butterflies.

genetics↗

bioRxiv2025

UGT35B1 is the principal enzyme mediating nicotine glycosylation in Drosophila melanogaster

Nicotine is a plant-derived pyridine alkaloid with potent neurotoxic properties. A major pathway for detoxification of nicotine in mammals is via glucuronidation to produce nicotine N-glucuronide, but this process in insects remains poorly understood. Using mass spectrometry, we demonstrate that Drosophila melanogaster detoxifies nicotine through glycosylation, producing nicotine N-glycoside. Given that many new agrochemicals contain pyridine rings, we also investigated the metabolism of flonicamid and imidacloprid. We detected glycosylation of flonicamid, but not imidacloprid. A targeted RNAi screen across 21 UDP-glycosyltransferases (Ugts) identified Ugt35B1 as important for survival of nicotine exposure. CRISPR-based knockout of Ugt35B1 increases sensitivity to nicotine and flonicamid, but not to imidacloprid, nor to a structurally distinct neonicotinoid (thiamethoxam). Mass spectrometry of knockout and control flies confirms that Ugt35B1 glycosylates nicotine, its metabolite cotinine, and flonicamid. Together these findings establish Ugt35B1 as the principal UGT mediating nicotine detoxification in D. melanogaster, revealing a previously uncharacterized insect glycosylation pathway with potential implications for herbivory, insecticide detoxification and toxicology. Highlights- Drosophila detoxifies nicotine by glycosylation into nicotine N-glycoside. - A targeted RNAi screen identifies Ugt35B1 as critical for nicotine survival. - Ugt35B1 knockout sensitizes flies to nicotine and flonicamid, but not to imidacloprid or thiamethoxam. - First demonstration of an insect UGT mediating in vivo glycosylation of nicotine and cotinine.

pharmacology and toxicology↗

bioRxiv2024

Tracking Helicoverpa zea (Lepidoptera: Noctuidae) flight behavior with infrared camera around pheromone trap

Understanding the flight behavior of nocturnal insect pests is essential for designing effective trapping systems and improving integrated pest management (IPM). This study used infrared (IR) reflectance and IR camera to analyze the flight behavior of corn earworm (Helicoverpa zea) around Scentry Heliothis pheromone trap, focusing on approach, escape, and capture rates. Video analysis revealed low average catch rate of 25% for a total of 48 approaches from 7 p.m. to 4 a.m., as many moths approached the lure but escaped without being trapped. The study identified critical behavioral patterns, such as upwind approach, downwind horizontal escape, or vertical ascending leading to capture. These findings suggest that positioning lure closer to the trap entrance could significantly improve the effectiveness of Scentry Heliothis trap. Additionally, the study highlights the importance of developing a comprehensive database of nocturnal insect behavior around trapping systems. This knowledge can be used to refine trap design for specific insect pest and to update catch count thresholds to improve the effectiveness of insecticide spray programs in precision agriculture. This work demonstrates the potential of IR cameras as a simple, commercially available, and affordable tool for studying nocturnal insect pest activity and flight behavior, with the potential to enhance pest management strategies in agriculture.

animal behavior and cognition↗

bioRxiv2020

Heterodimeric insecticidal peptide provides new insights into the molecular and functional diversity of ant venoms

Ants use venom for predation, defence and communication, however, the molecular diversity, function and potential applications of ant venom remains understudied compared to other venomous lineages such as arachnids, snakes and cone snails. In this work, we used a multidisciplinary approach that encompassed field work, proteomics, sequencing, chemical synthesis, structural analysis, molecular modelling, stability studies, and a series of in vitro and in vivo bioassays to investigate the molecular diversity of the venom of the Amazonian Pseudomyrmex penetrator ants. We isolated a potent insecticidal heterodimeric peptide {Delta}-pseudomyrmecitoxin-Pp1a ({Delta}-PSDTX-Pp1a) composed of a 27-residue long A-chain and a 33-residue long B-chain crosslinked by two disulfide bonds in an antiparallel orientation. We chemically synthesised {Delta}-PSDTX-Pp1a, its corresponding parallel AA and BB homodimers, and its monomeric chains and demonstrated that {Delta}-PSDTX-Pp1a had the most potent insecticidal effects in blow fly assays (LD50 = 3 nM). Molecular modelling and circular dichroism studies revealed strong alpha-helical features, indicating its cytotoxic effects could derive from membrane disruption, which was further supported by insect cell calcium assays. The native heterodimer was also substantially more stable against proteolytic degradation (t1/2 =13 h) than its homodimers or monomers (t1/2 <20 min), indicating an evolutionary advantage of the more complex structure. The proteomic analysis of Pseudomyrmex penetrator venom and in-depth characterisation of {Delta}-PSDTX-Pp1a provide novel insights in the structural complexity of ant venom, and further exemplifies how nature exploits disulfide-bond formation and dimerization to gain an evolutionary advantage via improved stability; a concept that is also highly relevant for the design and development of peptide therapeutics, molecular probes and bioinsecticides.

pharmacology and toxicology↗

bioRxiv2020

Assessing biosynthetic gene cluster diversity in a multipartite nutritional symbiosis between herbivorous turtle ants and conserved gut symbionts

In insect-microbe nutritional symbioses the symbiont supplements the low nutrient diet of the host by producing amino acids and vitamins, and degrading lignin or polysaccharides. In multipartite mutualisms composed of multiple symbionts from different taxonomical orders, it has been suggested that in addition to the genes involved in the nutritional symbiosis the symbionts maintain genes responsible for the production of metabolites putatively playing a role in the maintenance and interaction of the bacterial communities living in close proximity. To test this hypothesis we investigated the diversity of biosynthetic gene clusters (BGCs) in the genomes and metagenomes of obligate gut symbionts associated with the herbivorous turtle ants (genus: Cephalotes). We studied 17 Cephalotes species collected across several geographical areas to reveal that (i) mining bacterial metagenomes and genomes provides complementary results demonstrating the robustness of this approach with metagenomic data, (ii) symbiotic gut bacteria have a high diversity of BGCs which is correlated with host geography but not host phylogeny, (iii) the majority of the BGCs comes from the bacteria involved in the nutritional symbiosis supporting conserved metabolic functions for colonization, communication and competition in the gut environment, (iv) phylogenetic analysis of arylpolyene, polyketide (PK), and siderophore shows high similarity between BGCs of a single symbiont across different ant host species, while non-ribosomal peptide (NRP) shows high similarity between BGCs from different bacterial orders within a single host species suggesting multiple mechanisms for genome evolution of these obligate mutualistic gut bacteria.

evolutionary biology↗