Biology subjects

Lassance, J.-M.

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

10 recordsLinked to original sources

bioRxiv2026

Seeing danger? Visual constraints and collision risk in the Bearded Vulture Gypaetus barbatus

The Bearded Vulture, Gypaetus barbatus is highly vulnerable to collisions with human-made aerial infrastructures. Yet, its visual sensory system remains poorly understood, limiting the development of species-specific collision mitigation measures. To address this gap, we characterized its visual ecology across four complementary dimensions: visual fields, spatial resolution, contrast sensitivity and spectral sensitivity of cone visual rhodopsins. Bearded vultures have no blind area in the direction of travel during foraging flight, indicating that frontal visual-field limitations are unlikely to contribute to their risk of collisions. Their axial length predicts high spatial visual resolution, suggesting that insufficient spatial resolution is unlikely to be a primary cause of collisions. By contrast, Bearded Vultures display very low peak contrast sensitivity compared to other birds, which may limit their ability to detect objects when contrast with the background, or within the objects themselves, is low. Functional characterization of the four cone visual pigments indicated sensitivity spanning approximately 350-640 nm, with a potential chromatic-discrimination range from 400 to 602 nm. Together, these results identify that contrast sensitivity, rather than visual-field configuration or spatial resolution, is a key perceptual constraint to consider in collision mitigation of the Bearded Vulture. Visual markers should therefore maximize both internal contrast and brightness contrast against the surrounding environment. More broadly, our multidisciplinary approach highlights how birds differ substantially in how they perceive anthropogenic structures and illustrates the importance of incorporating species-specific sensory ecology into conservation efforts, especially in the design of collision-mitigation strategies.

ecology↗

bioRxiv2026

Reconstruction of a rare {triangleup}10 desaturation pathway enables production of yellow peach moth pheromone precursors in Camelina sativa

Sex pheromones are environmentally friendly alternatives to traditional insecticides for pest control. The high synthesis cost, however, has restricted large-scale application. Plant-based biofactories provide a promising, sustainable route for cost-effective production that could facilitate the broader use of pheromone-based pest control. Mating disruption of the yellow peach moth, Conogethes punctiferalis--a serious pest of fruit trees and field crops in East Asia--can be achieved using (E)-10-hexadecenal and (Z)-10-hexadecenal, two components of its sex pheromone. To enable rational reconstruction of the biosynthetic pathway towards these unusual fatty acid derivatives in heterologous production systems, we first elucidated their biosynthesis by combining in vivo labeling experiments, transcriptomics and functional characterization of candidate desaturase and reductase genes using Nicotiana benthamiana and yeast expression systems. We identified a rare {Delta}10 fatty acyl desaturase that catalyzes the production of both (E)-10- and (Z)-10-hexadecenoic acids, along with a downstream fatty acyl reductase with higher activity on the E isomer. We further introduced this {Delta}10 desaturase together with an acyl-ACP thioesterase-1 into Camelina sativa to redirect seed lipid metabolism towards the accumulation of the pheromone precursor fatty acids. After four generations of selection, we obtained stably inherited Camelina lines accumulating up to 4.7% of target fatty acids in total seed lipids, with individual seeds containing up to 8.3 g, without significant effects on plant growth or seed viability. These findings demonstrate how elucidating moth pheromone biosynthetic pathways can support the development of sustainable biotechnological production systems for pheromone-based pest management.

synthetic biology↗

bioRxiv2026

Paving the way for plant-based bioproduction of (Z)-13-octadecenoic moth pheromone compounds

Sex pheromones are eco-friendly agents to control pest insects. Yet, the cost of synthetic pheromone production has restricted their use essentially to high value crops. Plant-based bioproduction of pheromone compounds offers a promising and sustainable alternative, opening up for the deployment of pheromone-mediated pest control also in row crops. The rice leaffolder Cnaphalocrocis medinalis uses C18 pheromone compounds and is a major rice pest in South China. We demonstrate that the fatty acid precursor of the main C18 pheromone component of C. medinalis, (Z)-13-octadecenal, can be biotechnologically produced using the oilseed crop Camelina sativa. First, we used deuterium-labelling to establish an elongation-based pathway for pheromone precursor formation from hexadecanoic (palmitic) acid via desaturation to (Z)-11-hexadecenoic acid and elongation to (Z)-13-octadecenoic acid. Using transient expression in Nicotiana benthamiana, we identified a minimal pathway consisting of a {Delta}11 desaturase (CmedDES1), an elongase (CmedELO1), and a fatty acyl reductase (CmedFAR2) for the heterologous biosynthesis of long-chain pheromone monounsaturated C18 precursors in planta. Co-expression of the insect desaturases CmedDES1 or CsupYPAQ with the Camelina elongase CsaKCS1 in Nicotiana benthamiana resulted in higher production of Z13-18 products compared to co-expression with insect elongases. We finally engineered Camelina sativa seeds through seed-specific co-expression of the Z11-16-forming insect desaturase CsupYPAQ and CsaKCS1 elongase, enabling the accumulation of C18 fatty acid pheromone precursors. Our study paves the way for sustainable production of the sex pheromone of C. medinalis and other C18 monounsaturated pheromone precursors for crop protection.

synthetic biology↗

bioRxiv2025

Exploring the visual system of the black Grouse (Lyrurus tetrix): Combining experimental and molecular approaches to inform strategies for reducing collisions

Understanding the visual systems of birds can inform conservation efforts and mitigate the impact of collisions with man-made structures. Here we investigate the visual abilities of the black grouse Lyrurus tetrix (Galliformes: Phasianidae), a European mountain bird highly vulnerable to collisions with aerial infrastructures. Using behavioural assays, we show that black grouse have wide monocular lateral visual fields, extensive binocular overlap and a minimal blind area behind the head, altogether indicating the ability to detect aerial objects from different fields of view. The spatial resolution and contrast sensitivity of the black grouse are in the low avian range but align with the ecology of a prey species and allow to establish the limits of detection of an object size and contrast under variable environmental conditions. To characterize the range of wavelengths perceived, the four cone visual pigments (SWS1, SWS2, Rh2, and LW) were reconstituted and characterized functionally, showing detection of light across a spectral range spanning the visible spectrum up to 650 nm and with limited sensitivity below 400 nm. Combined with spectral and achromatic modelling analyses, our results inform on the limits of detection of aerial objects and the perception of existing visual markers, offering practical perspectives to continue mitigating black grouse collisions.

ecology↗

bioRxiv2023

Evolution of gene expression across brain regions in behaviorally divergent deer mice

The evolution of innate behaviors is ultimately due to genetic variation likely acting in the nervous system. Gene regulation may be particularly important because it can evolve in a modular brain-region specific fashion through the concerted action of cis- and trans-regulatory changes. Here, to investigate transcriptional variation and its regulatory basis across the brain, we perform RNA sequencing (RNA-Seq) on ten brain subregions in two sister species of deer mice (Peromyscus maniculatus and P. polionotus) - which differ in a range of innate behaviors, including their social system - and their F1 hybrids. We find that most of the variation in gene expression distinguishes subregions, followed by species. Interspecific differential expression (DE) is pervasive (52-59% of expressed genes), whereas the number of DE genes between sexes is modest overall ([~]3%). Interestingly, the identity of DE genes varies considerably across brain regions. Much of this modularity is due to cis-regulatory divergence, and while 43% of genes were consistently assigned to the same gene regulatory class across subregions (e.g., conserved, cis-, or trans-regulatory divergence), a similar number were assigned to two or more different gene regulatory classes. Together, these results highlight the modularity of gene expression differences and divergence in the brain, which may be key to explain how the evolution of brain gene expression can contribute to the astonishing diversity of animal behaviors.

evolutionary biology↗

bioRxiv2023

Convergent evolution of noxious heat sensing by TRPA5, a novel class of heat sensor in Rhodnius prolixus

As ectotherms, insects need a multifaceted repertoire of heat-sensitive receptors to monitor environmental temperatures and finely control behavioral thermoregulation. Here, we show that TRPA5 genes, a class of ankyrin transient receptor potential channels lost in genomes of model fruit flies or mosquitoes, are widespread across insect orders, and encode a previously uncharacterized type of heat receptors. We demonstrate that RpTRPA5B, a TRPA5 channel of the triatomine bug Rhodnius prolixus (Insect: Hemiptera), primary vector of Chagas disease, forms a homo-tetrameric channel displaying a uniquely high thermosensitivity. The channel biophysical determinants include a large channel activation enthalpy change (72 kcal/mol), a high temperature coefficient (Q10 = 25), and temperature-induced currents from 53 {degrees}C to 68 {degrees}C (T0.5= 58.6 {degrees}C) in vitro, similar to mammalian noxious TRPV heat receptors. Monomeric and tetrameric predictions of the ion channel architecture show reliable and conserved structural parallels with fruit fly dTRPA1, albeit depicting structural uniqueness from dTRPA, Painless and Pyrexia in the ankyrin repeat domain and the channel selectivity filter, potential modulator regions of functional characteristics of TRPs. The channel activation response, structural features and ubiquitous sensory tissue expression delineate a potential thermosensitive physiological niche close to that of Pyrexia genes, lost during the evolution of true bugs. Overall, the finding of TRPA5 genes as a class of temperature-activated receptor illustrates the dynamic evolution of a large family of insect molecular heat detectors, with TRPs as promising multimodal sensory targets for triatomine vector control.

evolutionary biology↗

bioRxiv2021

A novel enhancer of Agouti contributes to parallel evolution of cryptically colored beach mice

Identifying the genetic basis of repeatedly evolved traits provides a way to reconstruct their evolutionary history and ultimately investigate the predictability of evolution. Here, we focus on the oldfield mouse (Peromyscus polionotus), which occurs in the southeastern United States, where it exhibits considerable coat-color variation. Dorsal coats range from dark brown in mice inhabiting mainland habitat to near white on the white-sand beaches of the southeastern US, where light pelage has evolved independently on Floridas Gulf and Atlantic coasts as an adaptation to visually hunting predators. To facilitate genomic analyses in this species, we first generated a high-quality, chromosome-level genome assembly of P. polionotus subgriseus. Next, in a uniquely variable mainland population that occurs near beach habitat (P. p. albifrons), we scored 23 pigment traits and performed targeted resequencing in 168 mice. We find that variation in pigmentation is strongly associated with a ~2 kb region approximately 5 kb upstream of the Agouti-signaling protein (ASIP) coding region. Using a reporter-gene assay, we demonstrate that this regulatory region contains an enhancer that drives expression in the dermis of mouse embryos during the establishment of pigment prepatterns. Moreover, extended tracts of homozygosity in this region of Agouti indicate that the light allele has experienced recent and strong positive selection. Notably, this same light allele appears fixed in both Gulf and Atlantic coast beach mice, despite these populations being separated by >1,000km. Given the evolutionary history of this species, our results suggest that this newly identified Agouti enhancer allele has been maintained in mainland populations as standing genetic variation and from there has spread to, and been selected in, two independent beach mouse lineages, thereby facilitating their rapid and parallel evolution.

evolutionary biology↗

bioRxiv2021

Automated tracking reveals the social network of beach mice and their burrows

Evolutionary biologists have long sought to understand the selective pressures driving phenotypic evolution. While most experimental data come from the study of morphological evolution, we know much less about the ultimate drivers of behavioral variation. Among the most striking examples of behavioral evolution are the long, complex burrows constructed by oldfield mice (Peromyscus polionotus ssp.). Yet how these mice use burrows in the wild, and whether burrow length may affect fitness, remains unknown. A major barrier to studying behavior in the wild has been the lack of technologies to continuously monitor - in this case, nocturnal and underground - behavior. Here, we designed and implemented a novel radio frequency identification (RFID) system to track patterns of burrow use in a natural population of beach mice. We combine RFID monitoring with burrow measurements, genetic data, and social network analysis to uncover how these monogamous mice use burrows under fully natural ecological and social conditions. We first found that long burrows provide a more stable thermal environment and have higher juvenile activity than short burrows, underscoring the likely importance of long burrows for rearing young. We also find that adult mice consistently use multiple burrows throughout their home range and tend to use the same burrows at the same time as their genetic relatives, suggesting that inclusive fitness benefits may accrue for individuals that construct and maintain multiple burrows. Our study highlights how new automated tracking approaches can provide novel insights into animal behavior in the wild.

animal behavior and cognition↗

bioRxiv2020

Evolution of the Codling Moth Pheromone Through the Member of an Ancient Desaturase Expansion

Defining the origin of genetic novelty is central to our understanding of the evolution of novel traits. Diversification among fatty acid desaturase (FAD) genes has played a fundamental role in the introduction of structural variation in fatty acyl derivatives. Because of its central role in generating diversity in insect semiochemicals, the FAD gene family has become a model to study how gene family expansions can contribute to the evolution of lineage-specific innovations. Here we used the codling moth (Cydia pomonella) as a study system to decipher the proximate mechanism underlying the production of the {Delta}8{Delta}10 signature structure of Olethreutine moths. Biosynthesis of the codling moth sex pheromone, (E8,E10)-dodecadienol (codlemone), involves two consecutive desaturation steps, the first of which is unusual in that it generates an E9 unsaturation. The second step is also atypical: it generates a conjugated diene system from the E9 monoene C12 intermediate via 1,4-desaturation. Here we describe the characterization of the FAD gene acting in codlemone biosynthesis. We identify 27 FAD genes corresponding to the various functional classes identified in Insects and Lepidoptera. These genes are distributed across the C. pomonella genome in tandem arrays or isolated genes, indicating that the FAD repertoire consists of both ancient and recent duplications and expansions. Using transcriptomics, we show large divergence in expression domains: some genes appear ubiquitously expressed across tissue and developmental stages; others appear more restricted in their expression pattern. Functional assays using heterologous expression systems reveal that one gene, Cpo_CPRQ, which is prominently and exclusively expressed in the female pheromone gland, encodes an FAD that possesses both E9 and {Delta}8{Delta}10-desaturation activities. Phylogenetically, Cpo_CPRQ clusters within the Lepidoptera-specific {Delta}10/{Delta}11 clade of FADs, a classic reservoir of unusual desaturase activities in moths. Our integrative approach shows that the evolution of the signature pheromone structure of Olethreutine moths relied on a gene belonging to an ancient gene expansion. Members of other expanded FAD subfamilies do not appear to play a role in chemical communication. This advises for caution when postulating the consequences of lineage-specific expansions based on genomics alone.

evolutionary biology↗

bioRxiv2020

The evolution of red colour vision is linked to coordinated rhodopsin tuning in lycaenid butterflies

Colour vision is largely mediated by changes in number, expression, and spectral properties of rhodopsins, but the genetic mechanisms underlying adaptive shifts in spectral sensitivity remain largely unexplored. Using in vivo photochemistry, optophysiology, and in vitro functional assays, we link variation in eye spectral sensitivity at long wavelengths to species-specific absorbance spectra for LW opsins in lycaenid butterflies. In addition to loci specifying an ancestral green-absorbing rhodopsin with maximum spectral sensitivity ({lambda}max) at 520-530 nm in Callophrys sheridanii and Celastrina ladon, we find a novel form of red-shifted LW rhodopsin at {lambda}max = 565-570 nm in Arhopala japonica and Eumaeus atala. Furthermore, we show that Ca. sheridanii and Ce. ladon exhibit a smaller bathochromic shift at BRh2 (480-489 nm), and with the ancestral LW rhodopsin, cannot perceive visible red light beyond 600 nm. In contrast, molecular variation at the LW opsin in A. japonica and E. atala is coordinated with tuning of the blue opsin that also shifts sensitivity to longer wavelengths enabling colour discrimination up to 617 nm. We then use E. atala as a model to examine the interplay between red and blue spectral sensitivity. Owing to blue duplicate expression, the spatial distribution of opsin mRNAs within an ommatidium defines an expanded retinal stochastic mosaic of at least six opsin-based photoreceptor classes. Our mutagenesis in vitro assays with BRh1 ({lambda}max = 435 nm) chimeric blue rhodopsins reveal four main residues contributing to the 65 nm bathochromic shift towards BRh2 ({lambda}max = 500 nm). Adaptations in this four-opsin visual system are relevant for discrimination of conspecific reflectance spectra in E. atala. Together, these findings illustrate how functional changes at multiple rhodopsins contribute to the evolution of a broader spectral sensitivity and adaptation in visual performance. Significance StatementRhodopsins are photosensitive protein molecules that absorb specific wavelengths of incoming light and convey colour information in the visual system. We show that molecular evolution in a green insect opsin gene resulted in a shift in its maximal absorbance peak, enabling some lycaenid butterflies to use spectral energy of longer wavelengths (LW) to discriminate colours in the red spectrum better than relatives bearing ancestral green LW rhodopsins. Lycaenids also evolved a duplicate blue opsin gene, and we illustrate an example where species equipped with red LW rhodopsins shifted their blue sensitivity peak to longer wavelengths due to changes in several blue-tuning residues that have evolved repeatedly in different insect lineages. We demonstrate how changes at multiple vision genes in the insect eye effectively create a coordinated mechanism expanding spectral sensitivity for visually guided behaviours such as selecting host plants and mates.

evolutionary biology↗