Biology subjects

Lofstedt, C.

Publications and source records attributed to Lofstedt, C..

6 recordsLinked to original sources

bioRxiv2023

Female-biased expressed odorant receptor genes differentially tuned to repulsive or attractive plant volatile compounds in the turnip moths

Insects rely on their highly efficient and precise olfactory systems to find suitable mates, host plants and oviposition sites, and adapt to the changing environment. The odorant receptors (ORs) including pheromone receptors (PRs) play a vital role in this process. While extensive studies have been focusing on deorphanization of lepidopteran PR genes, the information on the ligand profiles of general ORs is still sparse. In the present study, we identified a repertoire of 61 ORs including the co-receptor Orco from antennal and ovipositor transcriptomes of the turnip moth Agrotis segetum, which clustered in all the major lepidopteran OR clades. We characterized the function of eight female-biased expressed ORs in Xenopus oocytes and found three ORs differentially tuned to plant volatile compounds that might be repulsive or attractive to the moths. AsegOR13 was broadly tuned to a number of herbivore-induced plant volatiles (HIPVs) while AsegOR20 was specific to citral; AsegOR17 was narrowly tuned to the alcohols, isoamyl alcohol, pentanol and benzyl alcohol, that are potentially attractive to moths. The orthologues of the three ORs in other moth species seem to share the conserved function. Our results support the hypothesis that insects recognize their host plants mostly by detecting the mixture of ubiquitous compounds, instead of taxonomically characteristic host compounds. The combination of narrowly and broadly tuned ORs will ensure both the accuracy of the most important odor signals and the plasticity of the olfactory system to the changes in the environment.

neuroscience↗

bioRxiv2022

Odorant receptor orthologues in conifer-feeding beetles display conserved responses to ecologically relevant odors

Insects are able to detect a plethora of olfactory cues using a divergent family of odorant receptors (ORs). Despite the divergent nature of this family, related species frequently express several evolutionarily conserved OR orthologues. In the largest order of insects, Coleoptera, it remains unknown whether OR orthologues have conserved or divergent functions in different species. Using HEK293 cells, we addressed this question through functional characterization of two groups of OR orthologues in three species of the Curculionidae (weevil) family, the conifer-feeding bark beetles Ips typographus L. ( Ityp) and Dendroctonus ponderosae Hopkins ( Dpon) (Scolytinae), and the pine weevil Hylobius abietis L. ( Habi; Molytinae). The ORs of H. abietis were annotated from antennal transcriptomes. Results show highly conserved response specificities, with one group of orthologues (HabiOR3/DponOR8/ItypOR6) responding exclusively to 2-phenylethanol (2-PE), and the other group (HabiOR4/DponOR9/ItypOR5) responding to angiosperm green leaf volatiles (GLVs). Both groups of orthologues belong to the coleopteran OR subfamily 2B, and share a common ancestor with OR5 in the cerambycid Megacyllene caryae, also tuned to 2-PE, suggesting a shared evolutionary history of 2-PE receptors across two beetle superfamilies. The detected compounds are ecologically relevant for conifer-feeding curculionids, and are probably linked to fitness, with GLVs being used to avoid angiosperm non-host plants, and 2-PE being important for intraspecific communication and/or playing a putative role in beetle-microbe symbioses. To our knowledge, this study is the first to reveal evolutionary conservation of OR functions across several beetle species and hence sheds new light on the functional evolution of insect ORs.

neuroscience↗

bioRxiv2021

Ionotropic receptors in the turnip moth Agrotis segetum respond to repellent medium-chain fatty acids

BackgroundIn insects, airborne chemical signals are mainly detected by two receptor families, odorant receptors (ORs) and ionotropic receptors (IRs). Functions of ORs have been intensively investigated in Diptera and Lepidoptera, while the functions and evolution of the more ancient IR family remain largely unexplored beyond Diptera. ResultsHere, we identified a repertoire of 26 IRs from transcriptomes of female and male antennae, and ovipositors in the moth Agrotis segetum. We observed that a large clade formed by IR75p and IR75q expansions is closely related to the acid-sensing IRs identified in Diptera. We functionally assayed each of the five AsegIRs from this clade using Xenopus oocytes and found that two receptors responded to the tested ligands. AsegIR75p.1 responded to several compounds but hexanoic acid was revealed to be the primary ligand, and AsegIR75q.1 responded primarily to octanoic acid, and less so to nonanoic acid. It has been reported that the C6-C10 medium-chain fatty acids repel various insects including many drosophilids and mosquitos. Our GC-EAD recordings showed that C6-C10 medium-chain fatty acids elicited antennal responses of both sexes of A. segetum, while only octanoic acid had repellent effect to the moths in a behavioural assay. In addition, using fluorescence in situ hybridization, we demonstrated that the five IRs and their co-receptor AsegIR8a are not located in coeloconic sensilla as found in Drosophila, but in basiconic or trichoid sensilla. ConclusionsOur results significantly expand the current knowledge of the insect IR family. Based on the functional data in combination with phylogenetic analysis, we propose that subfunctionalization after gene duplication plays an important role in the evolution of ligand specificities of the acid-sensing IRs in Lepidoptera.

evolutionary biology↗

bioRxiv2020

Functional evolution of a bark beetle odorant receptor clade detecting monoterpenoids of different ecological origins

Insects detect odors using an array of odorant receptors (ORs), which may expand through gene duplication. How specificities evolve and new functions arise in related ORs within a species remain poorly investigated. We addressed this question by functionally characterizing ORs from the Eurasian spruce bark beetle Ips typographus, in which antennal detection and behavioral responses to pheromones, volatiles from host and non-host trees, and fungal symbionts are well described. In contrast, knowledge of OR function is restricted to two receptors detecting the pheromone compounds (S)-(-)-ipsenol (ItypOR46) and (R)-(-)-ipsdienol (ItypOR49). These receptors belong to a species-specific OR-lineage comprising seven ItypORs. To gain insight into the functional evolution of related ORs, we characterized the five remaining ORs in this clade, using Xenopus oocytes. Two receptors responded primarily to the host tree monoterpenes (+)-3-carene (ItypOR25) and p-cymene (ItypOR27). Two receptors responded to oxygenated monoterpenoids produced in relatively large amounts by the beetle-associated fungi, with ItypOR23 specific for (+)-trans-(1R,4S)-4-thujanol, and ItypOR29 responding to (+)-isopinocamphone and similar ketones. ItypOR28 responded to the pheromone E-myrcenol from the competitor Ips duplicatus. Overall, the OR responses match well with those of previously characterized olfactory sensory neuron classes except that neurons detecting E-myrcenol have not been identified. The characterized ORs are under strong purifying selection and demonstrate a shared functional property in that they all primarily respond to monoterpenoids. The variation in functional groups among OR ligands and their diverse ecological origins suggest that neofunctionalization has occurred early in the evolution of this OR-lineage following gene duplication.

molecular biology↗

bioRxiv2020

A highly contiguous genome assembly of a major forest pest, the Eurasian spruce bark beetle Ips typographus

The Eurasian spruce bark beetle (Ips typographus [L.]), is a major killer of spruce forests across the Palearctic. During epidemics, it can destroy over 100 million cubic meters of spruce trees in a single year. Here we report a 236 Mb, highly contiguous I. typographus genome assembly using PacBio long-read sequencing. The final phased assembly had a contig N50 of 6.65 Mb in 272 contigs and was predicted to contain 23,923 protein-coding genes. Comparative genomic analysis revealed expanded gene families associated with plant cell wall degradation, including pectinases, aspartyl proteases, and glycosyl hydrolases. In todays forests, increasingly stressed by global warming, this resource can assist in mitigating bark beetle outbreaks by developing novel pest control strategies. Further, this first whole-genome sequence from the genus Ips provides timely resources to address important questions about the evolutionary biology and ecology of Curculionidae, the true weevils, one of the largest animal families.

genomics↗

bioRxiv2020

Putative ligand binding sites of two functionally characterized bark beetle odorant receptors

AO_SCPLOWBSTRACTC_SCPLOWBark beetle behavior is to a large extent mediated via olfaction. Targeting the odorant receptors (ORs) may thus provide avenues towards improved pest control during outbreaks. Such an approach requires information on the function of receptors and their interactions with ligands. Hence, we annotated 73 ORs from an antennal transcriptome of the spruce bark beetle Ips typographus and report the functional characterization of two ORs (ItypOR46 and ItypOR49), which are selective for single enantiomers of the common bark beetle pheromone compounds ipsenol and ipsdienol, respectively. We use homology modeling and molecular docking to predict their binding sites. The importance of residues Tyr84 and Thr205 in ItypOR46 in the activation by ipsenol is experimentally supported, and hydrogen bonding appears key in pheromone binding. The biological significance of the characterized ORs positions them as prime targets for pest control and use in biosensors to detect bark beetle infestations.

neuroscience↗