Molecular basis ofMorinda citrifolia (L.): Toxicity on drosophila

Legal, Luc; Chappe, B.; Jallon, Jean‐Marc

doi:10.1007/bf02066234

Cited by 82 publications

(95 citation statements)

References 7 publications

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“…The combination was gently agitated to ensure even distribution of the hydrophobic octanoic and hexanoic acids. Morinda fruit has a 3:1 ratio of octanoic to hexanoic acid (Legal et al 1994). The concentration of Morinda toxins in the medium was low relative to what is typically observed in nature, but not outside the normal range.…”

Section: Methodsmentioning

confidence: 82%

Genetic Changes Accompanying the Evolution of Host Specialization in Drosophila sechellia

2009

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Changes in host specialization contribute to the diversification of phytophagous insects. When shifting to a new host, insects evolve new physiological, morphological, and behavioral adaptations. Our understanding of the genetic changes responsible for these adaptations is limited. For instance, we do not know how often host shifts involve gain-of-function vs. loss-of-function alleles. Recent work suggests that some genes involved in odor recognition are lost in specialists. Here we show that genes involved in detoxification and metabolism, as well as those affecting olfaction, have reduced gene expression in Drosophila sechellia-a specialist on the fruit of Morinda citrifolia. We screened for genes that differ in expression between D. sechellia and its generalist sister species, D. simulans. We also screened for genes that are differentially expressed in D. sechellia when these flies chose their preferred host vs. when they were forced onto other food. D. sechellia increases expression of genes involved with oogenesis and fatty acid metabolism when on its host. The majority of differentially expressed genes, however, appear downregulated in D. sechellia. For several functionally related genes, this decrease in expression is associated with apparent loss-of-function alleles. For example, the D. sechellia allele of Odorant binding protein 56e (Obp56e) harbors a premature stop codon. We show that knockdown of Obp56e activity significantly reduces the avoidance response of D. melanogaster toward M. citrifolia. We argue that apparent loss-of-function alleles like Obp56e potentially contributed to the initial adaptation of D. sechellia to its host. Our results suggest that a subset of genes reduce or lose function as a consequence of host specialization, which may explain why, in general, specialist insects tend to shift to chemically similar hosts.

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Section: Methodsmentioning

confidence: 82%

Genetic Changes Accompanying the Evolution of Host Specialization in Drosophila sechellia

2009

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“…Thus, in D. sechellia, positive selection of Cyp12d3 may have occurred concurrently with its ecological specialization on its toxic host plant. Based on its signature of positive selection, we predict that Cyp12d3 in D. sechellia has evolved a function unique to this species, perhaps in the metabolism of toxic compounds in its host plant, such as octanoic or hexanoic acid (Amlou et al 1998;Legal et al 1994;Farine et al 1996). To test this hypothesis, the Cyp12d3 protein would need to be Fig.…”

Section: Discussionmentioning

confidence: 99%

Evolutionary Toxicogenomics: Diversification of the Cyp12d1 and Cyp12d3 Genes in Drosophila Species

et al. 2012

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“…Biogeographical and phylogenetic evidence suggests that this species evolved in isolation after colonization of these islands approximately half a million years ago by its sister species, Drosophila simulans (10, 11). Interestingly, whereas D. simulans is a quintessential generalist (12), D. sechellia feeds solely on fruit of the shrub Morinda citrifolia (13,14) and has evolved a remarkable chemical preference for (and resistance to) toxins that occur in Morinda and strongly repel other vinegar flies (15)(16)(17)(18). Although this novel preference may be related to an overabundance of two types of olfactory receptor neurons on D. sechellia antennae, the binding specificities and sensitivities of these neurons appear to remain unaltered in comparison to D. simulans (19,20).…”

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confidence: 99%

Rapid evolution of smell and taste receptor genes during host specialization in Drosophila sechellia

McBride

2007

Proc. Natl. Acad. Sci. U.S.A.

216

252

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Our understanding of the genetic basis of host specialization in insects is limited to basic information on the number and location of genetic factors underlying changes in conspicuous phenotypes. We know nothing about general patterns of molecular evolution that may accompany host specialization but are not traceable to a single prominent phenotypic change. Here, I describe changes in the entire repertoire of 136 olfactory receptor (Or) and gustatory receptor (Gr) genes of the recently specialized vinegar fly Drosophila sechellia. I find that D. sechellia is losing Or and Gr genes nearly 10 times faster than its generalist sibling Drosophila simulans. Moreover, those D. sechellia receptors that remain intact have fixed amino acid replacement mutations at a higher rate relative to silent mutations than have their D. simulans orthologs. Comparison of these patterns with those observed in a random sample of genes indicates that the changes at Or and Gr loci are likely to reflect positive selection and/or relaxed constraint associated with the altered ecological niche of this fly.comparative genomics ͉ gustatory receptor ͉ host adaptation ͉ lineage-specific ͉ olfactory receptor H ost specialization and host shifts in insects that feed on plants provide excellent opportunities to study the genetic basis of ecological adaptation. Until now, however, this endeavor has been limited to attempts to map factors responsible for conspicuous phenotypic changes that accompany the ecological shifts (e.g., refs. 1-5). We know nothing about genetic changes whose individual effects are subtle, but whose combined presence may leave a striking signature on the genomes of specializing or host-shifting insects.For example, insects evaluate their environment largely by smell and taste, and we might therefore expect their chemical sensory systems to evolve during host specialization or shifts. The acquisition of a novel host may drive the adaptive divergence of sensory systems by positive selection, and the abandonment of an ancestral host may result in the deterioration of older sensory adaptations by genetic drift (or positive selection). Despite their potentially subtle phenotypic effects, such changes are likely to be pervasive (particularly because new host plants challenge insects with the task of recognizing and responding not only to a new food but often also to novel toxins, bacteria, fungi, predators, parasitoids, pupation sites, and mating environments) and are best detected by examining entire genomes or large groups of genes simultaneously.The olfactory receptor (Or) and gustatory receptor (Gr) gene families encode a diverse group of transmembrane proteins that bind volatile and soluble chemicals from the environment and trigger nerve impulses to the brain (6). Individual receptor genes in insects are highly divergent (paralogous genes from a single species often sharing Ͻ20% of their amino acids), are expressed in narrow subsets of olfactory and gustatory neurons from well defined regions of smell and taste organs, and la...

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Molecular basis ofMorinda citrifolia (L.): Toxicity on drosophila

Cited by 82 publications

References 7 publications

Genetic Changes Accompanying the Evolution of Host Specialization in Drosophila sechellia

Genetic Changes Accompanying the Evolution of Host Specialization in Drosophila sechellia

Evolutionary Toxicogenomics: Diversification of the Cyp12d1 and Cyp12d3 Genes in Drosophila Species

Rapid evolution of smell and taste receptor genes during host specialization in Drosophila sechellia

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