Strigolactones are a recently discovered class of plant hormone involved in branching, leaf senescence, root development, and plant-microbe interactions 1–6. They are carotenoid-derived lactones, ...synthesized in the roots and transported acropetally to modulate axillary bud outgrowth (i.e., branching) 1, 2. However, a receptor for strigolactones has not been identified. We have identified the DAD2 gene from petunia, an ortholog of the rice and Arabidopsis D14 genes, and present evidence for its roles in strigolactone perception and signaling. DAD2 acts in the strigolactone pathway, and the dad2 mutant is insensitive to the strigolactone analog GR24. The crystal structure of DAD2 reveals an α/β hydrolase fold containing a canonical catalytic triad with a large internal cavity capable of accommodating strigolactones. In the presence of GR24 DAD2 interacts with PhMAX2A, a central component of strigolactone signaling, in a GR24 concentration-dependent manner. DAD2 can hydrolyze GR24, with mutants of the catalytic triad abolishing both this activity and the ability of DAD2 to interact with PhMAX2A. The hydrolysis products can neither stimulate the protein-protein interaction nor modulate branching. These observations suggest that DAD2 acts to bind the mobile strigolactone signal and then interacts with PhMAX2A during catalysis to initiate an SCF-mediated signal transduction pathway.
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► DAD2 gene, identified by transposon tagging, encodes an α/β hydrolase fold protein ► DAD2 acts in the shoot; mutants are insensitive to strigolactones ► DAD2 crystal structure shows an internal cavity capable of binding strigolactones ► DAD2 can hydrolyze the strigolactone GR24
Humans vary in acuity to many odors 1–4, with variation within olfactory receptor (OR) genes contributing to these differences 5–9. How such variation also affects odor experience and food selection ...remains uncertain 10, given that such effects occur for taste 11–15. Here we investigate β-ionone, which shows extreme sensitivity differences 4, 16, 17. β-ionone is a key aroma in foods and beverages 18–21 and is added to products in order to give a pleasant floral note 22, 23. Genome-wide and in vitro assays demonstrate rs6591536 as the causal variant for β-ionone odor sensitivity. rs6591536 encodes a N183D substitution in the second extracellular loop of OR5A1 and explains >96% of the observed phenotypic variation, resembling a monogenic Mendelian trait. Individuals carrying genotypes for β-ionone sensitivity can more easily differentiate between food and beverage stimuli with and without added β-ionone. Sensitive individuals typically describe β-ionone in foods and beverages as “fragrant” and “floral,” whereas less-sensitive individuals describe these stimuli differently. rs6591536 genotype also influences emotional associations and explains differences in food and product choices. These studies demonstrate that an OR variant that influences olfactory sensitivity can affect how people experience and respond to foods, beverages, and other products.
•A genetic variant, rs6591536, in OR5A1 determines sensitivity to β-ionone•rs6591536 alters β-ionone odor experience, both alone and in foods and beverages•rs6591536 affects acceptance and choice of food and products containing β-ionone
With the ever‐increasing number of publicly available eukaryotic genome assemblies and user‐friendly bioinformatics tools, there are increasing opportunities for researchers to use genomic resources ...in their research. While there are multiple dimensions to genome quality, it is often reduced to a single score that may not be correlated with other metrics, or appropriate for all applications of an assembly. To assess whether the commonly reported N50 value could reliably predict a separate dimension of genome quality, gene space completeness, we performed a meta‐analysis of 611 published articles on eukaryotic genomes that used BUSCO scores, in addition to the typical N50 score. We found that although assemblies with relatively high contig and scaffold N50 values consistently had high BUSCO scores, a high BUSCO score could also be obtained from assemblies with a low N50. This reinforces that despite its ubiquity, N50 is not a perfect proxy for all measures of genome accuracy. Our data also suggests that variations in BUSCO scores among assemblies with poor N50 scores may be related to the number of introns in conserved eukaryotic genes. We stress the importance of screening and evaluating assembly quality based on the appropriate tools and urge increased reporting of additional genome assessment metrics in addition to N50. We also discuss the potential limitations of BUSCO and suggest improvements for assessing gene space within genome assemblies.
Yeasts that invade and colonise fruit significantly enhance the volatile chemical diversity of this ecosystem. These modified bouquets are thought to be more attractive to Drosophila flies than the ...fruit alone, but the variance of attraction in natural yeast populations is uncharacterised. Here we investigate how a range of yeast isolates affect the attraction of female D. melanogaster to fruit in a simple two choice assay comparing yeast to sterile fruit. Of the 43 yeast isolates examined, 33 were attractive and seven repellent to the flies. The results of isolate-versus-isolate comparisons provided the same relative rankings. Attractiveness varied significantly by yeast, with the strongly fermenting Saccharomyces species generally being more attractive than the mostly respiring non-Saccharomyces species (P = 0.0035). Overall the habitat (fruit or other) from which the isolates were directly sampled did not explain attraction (P = 0.2352). However, yeasts isolated from fruit associated niches were more attractive than those from non-fruit associated niches (P = 0.0188) regardless of taxonomic positioning. These data suggest that while attractiveness is primarily correlated with phylogenetic status, the ability to attract Drosophila is a labile trait among yeasts that is potentially associated with those inhabiting fruit ecosystems. Preliminary analysis of the volatiles emitted by four yeast isolates in grape juice show the presence/absence of ethanol and acetic acid were not likely explanations for the observed variation in attraction. These data demonstrate variation among yeasts for their ability to attract Drosophila in a pattern that is consistent with the hypothesis that certain yeasts are manipulating fruit odours to mediate interactions with their Drosophila dispersal agent.
Humans vary in their ability to smell numerous odors 1–3, including those associated with food 4–6. Odor sensitivity is heritable 7–11, with examples linking genetic variation for sensitivity to ...specific odors typically located near olfactory receptor (OR) genes 12–16. However, with thousands of aromas and few deorphaned ORs 17, 18, there has been little progress toward linking variation at OR loci to odor sensitivity 19, 20. We hypothesized that OR genes contain the variation that explains much of the differences in sensitivity for odors, paralleling the genetics of taste 21, 22, which affect the flavor experience of foods 23–25. We employed a genome-wide association approach for ten food-related odors and identified genetic associations to sensitivity for 2-heptanone (p = 5.1 × 10−8), isobutyraldehyde (p = 6.4 × 10−10), β-damascenone (p = 1.6 × 10−7), and β-ionone (p = 1.4 × 10−31). Each locus is located in/near distinct clusters of OR genes. These findings increase the number of olfactory sensitivity loci to nine and demonstrate the importance of OR-associated variation in sensory acuity for food-related odors. Analysis of genotype frequencies across human populations implies that variation in sensitivity for these odors is widespread. Furthermore, each participant possessed one of many possible combinations of sensitivities for these odors, supporting the notion that everyone experiences their own unique “flavor world.”
•Sensitivity to four odors showed genetic associations•All regions associated with sensitivity lie near olfactory receptor clusters•Combinations of odor sensitivities show diversity of sensitivity profiles
The lightbrown apple moth, Epiphyas postvittana is an increasingly global pest of horticultural crops. Like other moths, E. postvittana relies on olfactory cues to locate mates and oviposition sites. ...To detect these cues, moths have evolved families of genes encoding elements of the peripheral olfactory reception system, including odor carriers, receptors and degrading enzymes. Here we undertake a transcriptomic approach to identify members of these families expressed in the adult antennae of E. postvittana, describing open reading frames encoding 34 odorant binding proteins, 13 chemosensory proteins, 70 odorant receptors, 19 ionotropic receptors, nine gustatory receptors, two sensory neuron membrane proteins, 27 carboxylesterases, 20 glutathione-S-transferases, 49 cytochrome p450s and 18 takeout proteins. For the odorant receptors, quantitative RT-PCR corroborated RNAseq count data on steady state transcript levels. Of the eight odorant receptors that group phylogenetically with pheromone receptors from other moths, two displayed significant male-biased expression patterns, one displayed significant female-biased expression pattern and five were expressed equally in the antennae of both sexes. In addition, we found two male-biased odorant receptors that did not group with previously described pheromone receptors. This suite of olfaction-related genes provides a substantial resource for the functional characterization of this signal transduction system and the development of odor-mediated control strategies for horticultural pests.
Niche construction theory explains how organisms' niche modifications may feed back to affect their evolutionary trajectories. In theory, the evolution of other species accessing the same modified ...niche may also be affected. We propose that this niche construction may be a general mechanism driving the evolution of mutualisms. Drosophilid flies benefit from accessing yeast‐infested fruits, but the consequences of this interaction for yeasts are unknown. We reveal high levels of variation among strains of Saccharomyces cerevisiae in their ability to modify fruits and attract Drosophila simulans. More attractive yeasts are dispersed more frequently, both in the lab and in the field, and flies associated with more attractive yeasts have higher fecundity. Although there may be multiple natural yeast and fly species interactions, our controlled assays in the lab and field provide evidence of a mutualistic interaction, facilitated by the yeast's niche modification.
Insects have co-opted a unique family of seven transmembrane proteins for odour sensing. Odorant receptors are believed to have evolved from gustatory receptors somewhere at the base of the Hexapoda ...and have expanded substantially to become the dominant class of odour recognition elements within the Insecta. These odorant receptors comprise an obligate co-receptor, Orco, and one of a family of highly divergent odorant “tuning” receptors. The two subunits are thought to come together at some as-yet unknown stoichiometry to form a functional complex that is capable of both ionotropic and metabotropic signalling. While there are still no 3D structures for these proteins, site-directed mutagenesis, resonance energy transfer, and structural modelling efforts, all mainly on Drosophila odorant receptors, are beginning to inform hypotheses of their structures and how such complexes function in odour detection. Some of the loops, especially the second extracellular loop that has been suggested to form a lid over the binding pocket, and the extracellular regions of some transmembrane helices, especially the third and to a less extent the sixth and seventh, have been implicated in ligand recognition in tuning receptors. The possible interaction between Orco and tuning receptor subunits through the final intracellular loop and the adjacent transmembrane helices is thought to be important for transducing ligand binding into receptor activation. Potential phosphorylation sites and a calmodulin binding site in the second intracellular loop of Orco are also thought to be involved in regulating channel gating. A number of new methods have recently been developed to express and purify insect odorant receptor subunits in recombinant expression systems. These approaches are enabling high throughput screening of receptors for agonists and antagonists in cell-based formats, as well as producing protein for the application of biophysical methods to resolve the 3D structure of the subunits and their complexes.
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•Insect ORs are non-selective cation channels consisting of an odorant binding subunit and an ion channel forming subunit.•OrX specificity ranges from broadly to narrowly tuned for their target odorants.•Evolutionary coupling derived structure models indicate features associated with odorant binding and ion channel function.•Channel gating is thought to be regulated by ligand-binding, calmodulin binding and phosphorylation.
Olfactory receptors (ORs) are the key elements of the molecular machinery responsible for the detection of odors in insects. Since their initial discovery in Drosophila melanogaster at the beginning ...of the twenty-first century, insect ORs have been the focus of intense research, both for fundamental knowledge of sensory systems and for their potential as novel targets for the development of products that could impact harmful behaviors of crop pests and disease vectors. In recent years, studies on insect ORs have entered the genomic era, with an ever-increasing number of OR genes being characterized every year through the sequencing of genomes and transcriptomes. With the upcoming release of genomic sequences from hundreds of insect species, the insect OR family could very well become the largest multigene family known. This extremely rapid identification of ORs in many insects is driving the necessity for the development of high-throughput technologies that will allow the identification of ligands for this unprecedented number of receptors. Moreover, such technologies will also be important for the development of agonists or antagonists that could be used in the fight against pest insects.
Employs de novo transcriptome analysis to identify genes with primary functions related to female odour reception, digestion, and male sexual traits in the New Zealand common stick insect Clitarchus ...hookeri (White). Source: National Library of New Zealand Te Puna Matauranga o Aotearoa, licensed by the Department of Internal Affairs for re-use under the Creative Commons Attribution 3.0 New Zealand Licence.
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