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DGIMI - Diversity, Genomes and Insects-Microorganisms Interactions

DGIMI is a joint research unit supervised by INRAE and the University of Montpellier. It is located on the Triolet campus of the University of Montpellier, and houses staff from both INRAE and UM.

The research carried out by UMR DGIMI is devoted to the study of interaction mechanisms between insect crop pests, their pathogens and parasites, and their host plants. This research takes into account the diversity of the partners and is based on knowledge of their genomes.

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HAL : Dernières publications

  • [hal-05625613] Priority effects drive fungal and nematode emergence from insect larvae

    Abstract Priority effects, in which species arrival history influences community assembly, are increasingly recognized to affect host–parasite systems. However, priority effects across disparate groups of parasitic organisms are poorly understood despite the wide range of taxonomic groups involved. In California oak woodland, we investigated how priority effects between two insect-parasitic fungi (Metarhizium and Beauveria) influenced emergence of nematodes from insect larvae. Field and laboratory results indicated that both fungi were common, but priority effects prevented them from co-emerging from the same larva. Metarhizium- and Beauveria-infected insects did not differ in the species composition of emerging nematodes, but larvae without fungal emergence had distinct nematode communities, with Oscheius almost always emerging without fungi. Experiments indicated that none of the commonly found nematodes (Acrobeloides, Mesorhabditis, Oscheius, and Rhabditis) were entomopathogenic, but that Oscheius could exclude Beauveria if it arrived early. This time-dependent exclusion was likely caused by a bacterium that Oscheius nematodes carried (Serratia proteamaculans). Together, these findings suggest that fungi enter insects as primary arrivers, while nematodes come as secondary arrivers to exploit fungus-killed insects, with priority effects influencing both groups. We suggest that this system is a promising natural microcosm for understanding priority effects across disparate groups in host–parasite systems.

    ano.nymous@ccsd.cnrs.fr.invalid (Amaury Payelleville) 18 May 2026

    https://hal.science/hal-05625613v1
  • [hal-05651879] Argonaute protein and small RNA expression patterns in Spodoptera frugiperda (Lepidoptera, Noctuidae)

    PIWI-interacting RNAs (piRNAs) and PIWI proteins were initially described as playing a role in gametogenesis and maintaining genome integrity by controlling transposable elements (TEs). Expressed also in the soma and able to regulate protein coding gene expression, they are involved in multiple biological pathways, including host-pathogens interaction, sex determination and reproductive isolation. Spodoptera frugiperda (Sf) is a major invasive insect pest species consisting of two strains with distinct host-plant ranges. To identify which pathway was regulated by piRNAs in this species, we characterized proteins and genomic regions involved in their biogenesis, as well as TE and gene transcripts regulated. By phylogenetic analysis, we identified two new Piwi genes conserved in the genus Spodoptera, compared to the Lepidopteran model Bombyx mori, one more than in Drosophila. One of them, more expressed in the gonads than in the soma, could be a functional homolog of Drosophila PIWI or replace AGO3. A pool of 11 sRNA-Seq libraries was used to annotate piRNA clusters with ShortStack in the genomes of the two Sf strains. Identification of TE targeted by putative piRNAs revealed that active transposons may differ between the two Sf strains, despite a similar TE content, as a putative cause or consequence of reproductive isolation. GO analysis of genes targeted by piRNAs shows that some are involved in protein translation initiation. A piRNA cluster in the Masc gene suggests that sex determination is regulated by piRNAs. Our analysis contributes to functional annotation of the Sf strains genomes and supports additional roles than silencing of transposable elements for piRNAs.

    ano.nymous@ccsd.cnrs.fr.invalid (Imène Séninet) 10 Jun 2026

    https://hal.science/hal-05651879v1
  • [hal-05595327] Poly-immunity arrays associated with Rhs toxins confer wide protection against competitors

    Bacterial genomes evolve under intense competition with diverse microorganisms. Polymorphic toxins are one of the best examples for demonstrating the intensity of this process. They comprise hypervariable C-terminal domains, encoding a broad range of toxic activities. These toxins are typically accompanied by highly specific immunity proteins encoded immediately downstream, which protect the producing bacteria from self-intoxication or fratricide. Here, we show that Photorhabdus and Xenorhabdus spp. genomes harbor extensive arrays of clustered immunity genes encoding proteins that neutralize type VI secretion system (T6SS) rearrangement hot spot (Rhs) polymorphic toxins secreted by closely related species. These immunity genes derive from ancient toxin-immunity pairs, yet only the immunity components are conserved, highlighting their protective role. Consistent with this, many of these immunity genes are expressed under steady-state conditions. Finally, we identify novel genetic elements conserved in several bacterial genera, termed Xer passenger cassettes (XPCs), which associate with both Rhs and the contact-dependent growth inhibition (CDI) polymorphic toxins, suggesting a potential role in their diversification and horizontal dissemination.

    ano.nymous@ccsd.cnrs.fr.invalid (Julius Martinkus) 17 Apr 2026

    https://hal.science/hal-05595327v1

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