Biology subjects

Degrave, A.

Publications and source records attributed to Degrave, A..

5 recordsLinked to original sources

bioRxiv2025

Comprehensive annotation of olfactory and gustatory receptor genes and transposable elements revealed their evolutionary dynamics in aphids

Understanding the molecular evolution of genes involved in parasite adaptation and the role of transposable elements (TEs) in driving their diversification is key to unraveling how populations adapt to their environments. In phytophagous insects like aphids, olfactory (OR) and gustatory receptor (GR) genes are crucial for host recognition, yet their post-duplication evolution remains insufficiently explored. Here, we analyzed 521 OR and 399 GR genes, alongside TEs, across 12 aphid genomes with varying host ranges. Aphid lineages with broader host ranges exhibited higher evolutionary rates, driven by gene family expansions linked to host interaction, including lipid metabolism, immune function, and transposase activity. The evolution of OR and GR genes post-duplication was shaped by diversifying selection, with bursts of positive selection followed by long periods of purifying selection, consistent with adaptation to new hosts. OR and GR genes originated from proximal and tandem duplications, with younger TE activity enriched near these genes compared to other genomic regions, suggesting a role for TEs in catalyzing tandem duplications and fueling diversification. The star-like topology of the OR phylogenetic tree, low synteny, and recent TE activity around OR genes support a faster evolutionary rate for ORs than GRs - a trend observed in other insect taxa. This study provides insights into molecular mechanisms underlying host adaptation in aphids and presents the first high-quality genome assembly of Dysaphis plantaginea, a major apple pest, with a comprehensive annotation of chemosensory genes and TEs. These resources offer a foundation for research on aphid genome evolution, insect-plant interactions.

molecular biology↗

bioRxiv2025

Welcome pathogens: transient heat dampens the responses to acibenzolar-S-methyl beyond defenses in apple plants

Climate change affects plant-pathogen interactions, with disease outcome varying depending on pathosystem and environmental scenario. In Arabidopsis, a thermo-sensitive module of salicylic acid (SA) signaling makes immunity vulnerable to heat. The potent resistance inducer acibenzolar-S-methyl (ASM), an SA analogue that up-regulates transcription of defense genes, could restore plant protection under heat but not core SA signaling. Here, we investigated how high temperature rewires the ASM-induced responses of the apple immune system. We treated apple plants with ASM under contrasting heatwave scenarios and subsequently exposed them to Erwinia amylovora (the fire blight bacterium) or Venturia inaequalis (the apple scab fungus) while monitoring gene expression. While pre-exposing apple plants to high temperature did not change their susceptibility to pathogens, it drove a loss of ASM-induced protection. Transcriptomic analysis revealed broad dampening of ASM-regulation upon high temperature, for a wide range of biological processes beyond defense. We uncovered thermo-sensitive "resistance" and "susceptibility" marker genes with ASM-responsiveness being critically vulnerable to heat. We concluded that exposure to heatwave prevents ASM from fully mounting its protective responses in apple, not only lowering defenses but also offering more favorable hosting conditions. Our work highlights plant immunity as the joint outcome of resistant and susceptible responses. Summary StatementWe found that heatwaves "disarm" apples ability to mount an effective inducible-immunity response against two major diseases, fire blight and apple scab. Heatwaves not only prevent full expression of plant defenses, but also favor a physiological status that is beneficial to the pathogens.

plant biology↗

bioRxiv2024

Dual NBT Approach: Gene Editing and Intragenesis to promote Fire Blight Resistance in Apple using MdAGG defense lectins.

Fire blight, caused by the bacterium Erwinia amylovora, represents a significant threat to apple (Malus domestica) production. Currently, only a limited number of genes effectively involved in resistance to E. amylovora have been identified. Seeking new resistance candidates, we focused on a multigene family encoding amaranthin-like lectins, which are highly upregulated following chemical elicitation by acibenzolar-S-methyl (ASM). These lectins are believed to contribute to downstream defense by promoting bacterial aggregation, which led to their designation as M. domestica agglutinins (MdAGG). When loss-of-function editions were introduced into MdAGG genes, the plants ability to mount a fully effective defense response against fire blight upon ASM treatment was compromised, confirming the role of MdAGGs in fire blight resistance. Next, we coupled the pPPO16 promoter, endogenous to apple and known to be rapidly induced during E. amylovora infection, with the coding sequence of MdAGG10 to create apple lines with fire blight-inducible MdAGG10 expression. Early MdAGG10 expression in these lines significantly improved resistance to fire blight, and an additional ASM treatment further enhanced this resistance. In summary, we conclude that MdAGGs act as defense genes whose timely expression can provide effective resistance against E. amylovora.

plant biology↗

bioRxiv2023

Overexpression of an apple broad range agglutinating lectin does not promote in planta resistance to fire blight and bacterial wilt.

Lectins, a large group of proteins present in all kingdoms of life can bind reversibly to glycans. The roles of plant lectins are diverse and include resistance to biotic or abiotic stress, notably bacterial resistance. A gene family encoding amaranthin-like lectins termed MdAGGs in apple (Malus domestica) has been identified to be overexpressed upon treatment with the plant resistance inducer acibenzolar-S-methyl (ASM) which promotes enhanced resistance to the fire blight disease caused by Erwinia amylovora (Ea). In this study, we first screened the ability of purified MdAGG10 to agglutinate bacterial cells in vitro among a range of bacterial species. Several bacterial species, either Gram positive or negative, either plant- or human-pathogens were found to be agglutinated by MdAGG10 in acidic conditions. Apple and Arabidopsis lines constitutively overexpressing MdAGG10 were generated and evaluated for their resistance to, respectively, Ea and Ralstonia solanacearum, both plant pathogens that were found in our screening. Despite MdAGG10 protein accumulated in tissues of both apple and Arabidopsis lines, they remained susceptible to their respective pathogens. Interestingly, in vitro agglutination of Ea by MdAGG10 did not impair bacterial growth, suggesting that other plant molecules are involved in the resistance to fire blight triggered after an ASM treatment.

plant biology↗

bioRxiv2020

Large-scale geographic survey provides insights into the colonization history of a major aphid pest on its cultivated apple host in Europe, North America and North Africa

AO_SCPLOWBSTRACTC_SCPLOWWith frequent host shifts involving the colonization of new hosts across large geographical ranges, crop pests are good models for examining the mechanisms of rapid colonization. The microbial partners of pest insects may also be involved in or affected by colonization processes, which has been little studied so far. We investigated the demographic history of the rosy apple aphid, Dysaphis plantaginea, a major pest of the cultivated apple (Malus domestica) in Europe, North Africa and North America, as well as the diversity of its microbiota. We genotyped a comprehensive sample of 714 colonies from Europe, Morocco and the US using mitochondrial (CytB and CO1), bacterial (16s rRNA and TrnpB), and 30 microsatellite markers. We detected five populations spread across the US, Morocco, Western and Eastern Europe and Spain. Populations showed weak genetic differentiation and high genetic diversity, except the ones from Morocco and North America that are likely the result of recent colonization events. Coalescent-based inferences revealed high levels of gene flow among populations during the colonization but did not allow determining the sequence of colonization of Europe, North America and Morroco by D. plantaginea, likely because of the weak genetic differentiation and the occurrence of gene flow among populations. We found that D. plantaginea rarely hosts other endosymbiotic bacteria than its obligate nutritional symbiont Buchnera aphidicola. This suggests that secondary endosymbionts did not play an important role in the rapid spread of the rosy apple aphid. These findings have fundamental importance for understanding pest colonization processes and implications for sustainable pest control programs.

evolutionary biology↗