Biology subjects

Gibert, J.-M.

Publications and source records attributed to Gibert, J.-M..

3 recordsLinked to original sources

bioRxiv2026

The histone demethylase Kdm5 and the ARGONAUTE proteins Piwi and Aubergine regulate female abdominal pigmentation in Drosophila melanogaster

Insect pigmentation is an ecologically critical trait influencing many physiological processes. In Drosophila melanogaster, abdominal pigmentation is sexually dimorphic: males have fully pigmented posterior segments, while females exhibit a posterior melanin stripe. Pigmentation relies on the expression of pigmentation genes that encode enzymes involved in pigment synthesis. These genes are tightly regulated during pupal and young adult stages. To expand the gene regulatory network of pigmentation genes, we conducted an RNAi screen using the yellow-Gal4 driver, expressed during the pupal stage in abdominal epidermis. One of the candidates from this screen, Kdm5, encodes a histone demethylase erasing the H3K4me3 histone mark catalyzed by the histone methyl-transferase Trithorax (Trx). We show that Kdm5 down-regulation reduces abdominal pigmentation, mimicking trx down-regulation. Kdm5 activates melanin production through regulation of the pigmentation gene tan. Transcriptomic analyses reveal that Kdm5 and Trx share many targets in pupal abdominal epidermis, including piRNA pathway components such as piwi and aubergine. These piRNA components, originally associated with transposon silencing in the germline, also function in some somatic tissues such as the nervous system, the fat body or the gut. We demonstrate that Piwi and Aubergine participate in female abdominal pigmentation establishment, without evident piRNA production. We also show that Kdm5 and Piwi act not only in pupal abdominal epidermis but also in pupal fat body. This study therefore expands the regulatory network of pigmentation genes. It identifies a new somatic function for Kdm5 and Piwi and reveals a role for pupal fat body in female abdominal pigmentation regulation.

genetics↗

bioRxiv2025

Genome-wide screen for deficiencies modifying Cyclin G-induced developmental instability in Drosophila melanogaster.

Despite long-lasting interest and research efforts, the genetic bases of developmental stability - the robustness to developmental noise - and its most commonly used estimator, fluctuating asymmetry (FA), remain poorly understood. The Drosophila melanogaster Cyclin G gene (CycG) encodes a transcriptional cyclin that regulates growth and the cell cycle. Over-expression of a potentially more stable isoform of the protein (deleted of a PEST-rich domain, hereafter called CycG{Delta}P) induces extreme wing size and shape FA (i.e. high developmental noise), indicating a major disruption of developmental stability. Previous attempts to identify the genetic bases of FA have been impeded by the constitutively low level of developmental noise, limiting the power to detect any effect. Here, we leverage the extreme developmental instability induced by overexpression of CycG{Delta}Pto explore the genetic bases of FA: we perform a genome-wide screen for deficiencies that enhance or reduce CycG{Delta}P-induced wing FA. 499 deficiencies uncovering 90% of the euchromatic genome were combined with a recombinant chromosome expressing CycG{Delta}P. We identified 13 and 16 deficiencies that respectively enhance and decrease FA. Analysis of mutants for some genes located in these deficiencies shows that Cyclin G ensures homogeneous growth of organs in synergy with the major morphogens of the wing, Dpp and Wg, as well as the Hippo and InR/TOR pathways. They also reveal that CycG{Delta}P-induced FA involves Larp, a potential direct interactor of Cyclin G, that regulates translation at the mitochondrial membrane. This opens up new research perspectives for understanding developmental stability, suggesting a significant role for mitochondrial activity.

genetics↗

bioRxiv2022

Drosophilid cuticle pigmentation impacts body temperature

Cuticle pigmentation has been clearly demonstrated to impact body temperature for several relatively large species of insects, but it was questioned for small insects. Here we used a thermal camera to assess the impact of drosophilid cuticle pigmentation on body temperature when individuals are exposed to light. We compared mutants of large effects within species (Drosophila melanogaster ebony and yellow mutants). Then we analyzed the impact of naturally occurring pigmentation variation within species complexes (Drosophila americana/Drosophila novamexicana and Drosophila yakuba/Drosophila santomea). Finally we analyzed lines of D. melanogaster with moderate differences in pigmentation. We found significant differences in temperatures for each of the four pairs we analyzed. The temperature differences appeared to be proportional to the differently pigmented area: between Drosophila melanogaster ebony and yellow mutants or between Drosophila americana and Drosophila novamexicana, for which the whole body is differently pigmented, the difference in temperatures was around 0.6{degrees}C {+/-}0.2{degrees}C. By contrast, between D. yakuba and D. santomea or between Drosophila melanogaster Dark and Pale lines, for which only the posterior abdomen is differentially pigmented, we detected a temperature difference of about 0.14{degrees}C {+/-}0.10{degrees}C. This demonstrates that cuticle pigmentation has ecological implications in drosophilids regarding adaptation to environmental temperature.

evolutionary biology↗