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Wild African Drosophila melanogaster Are Seasonal Specialists on Marula Fruit.

ABSTRACT: Although the vinegar fly Drosophila melanogaster is arguably the most studied organism on the planet, fundamental aspects of this species' natural ecology have remained enigmatic [1]. We have here investigated a wild population of D. melanogaster from a mopane forest in Zimbabwe. We find that these flies are closely associated with marula fruit (Sclerocarya birrea) and propose that this seasonally abundant and predominantly Southern African fruit is a key ancestral host of D. melanogaster. Moreover, when fruiting, marula is nearly exclusively used by D. melanogaster, suggesting that these forest-dwelling D. melanogaster are seasonal specialists, in a similar manner to, e.g., Drosophila erecta on screw pine cones [2]. We further demonstrate that the main chemicals released by marula activate odorant receptors that mediate species-specific host choice (Or22a) [3, 4] and oviposition site selection (Or19a) [5]. The Or22a-expressing neurons-ab3A-respond strongly to the marula ester ethyl isovalerate, a volatile rarely encountered in high amounts in other fruit. We also show that Or22a differs among African populations sampled from a wide range of habitats, in line with a function associated with host fruit usage. Flies from Southern Africa, most of which carry a distinct allele at the Or22a/Or22b locus, have ab3A neurons that are more sensitive to ethyl isovalerate than, e.g., European flies. Finally, we discuss the possibility that marula, which is also a culturally and nutritionally important resource to humans, may have helped the transition to commensalism in D. melanogaster.

SUBMITTER: Mansourian S

PROVIDER: S-EPMC7065024 | biostudies-literature | 2018 Dec

REPOSITORIES: biostudies-literature

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Wild African Drosophila melanogaster Are Seasonal Specialists on Marula Fruit.

Mansourian Suzan S Enjin Anders A Jirle Erling V EV Ramesh Vedika V Rehermann Guillermo G Becher Paul G PG Pool John E JE Stensmyr Marcus C MC

Current biology : CB 20181206 24

Although the vinegar fly Drosophila melanogaster is arguably the most studied organism on the planet, fundamental aspects of this species' natural ecology have remained enigmatic [1]. We have here investigated a wild population of D. melanogaster from a mopane forest in Zimbabwe. We find that these flies are closely associated with marula fruit (Sclerocarya birrea) and propose that this seasonally abundant and predominantly Southern African fruit is a key ancestral host of D. melanogaster. Moreo ...[more]

PMID: 30528579

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Project description:Drosophila melanogaster has played a pivotal role in the development of modern population genetics. However, many basic questions regarding the demographic and adaptive history of this species remain unresolved. We report the genome sequencing of 139 wild-derived strains of D. melanogaster, representing 22 population samples from the sub-Saharan ancestral range of this species, along with one European population. Most genomes were sequenced above 25X depth from haploid embryos. Results indicated a pervasive influence of non-African admixture in many African populations, motivating the development and application of a novel admixture detection method. Admixture proportions varied among populations, with greater admixture in urban locations. Admixture levels also varied across the genome, with localized peaks and valleys suggestive of a non-neutral introgression process. Genomes from the same location differed starkly in ancestry, suggesting that isolation mechanisms may exist within African populations. After removing putatively admixed genomic segments, the greatest genetic diversity was observed in southern Africa (e.g. Zambia), while diversity in other populations was largely consistent with a geographic expansion from this potentially ancestral region. The European population showed different levels of diversity reduction on each chromosome arm, and some African populations displayed chromosome arm-specific diversity reductions. Inversions in the European sample were associated with strong elevations in diversity across chromosome arms. Genomic scans were conducted to identify loci that may represent targets of positive selection within an African population, between African populations, and between European and African populations. A disproportionate number of candidate selective sweep regions were located near genes with varied roles in gene regulation. Outliers for Europe-Africa F(ST) were found to be enriched in genomic regions of locally elevated cosmopolitan admixture, possibly reflecting a role for some of these loci in driving the introgression of non-African alleles into African populations.

Project description:Abstract African Jointfir (Gnetum africanum) and Editan (Lasianthera africana) leaves are two leafy green veggies with several nutritional and medicinal properties. Alzheimer's disease (AD) is a form of neurodegeneration that is believed to cause dementia in affected individuals. The quest for alternative treatments has necessitated the exploitation of plants' secondary metabolites. Plant alkaloids have recently demonstrated relevance in the management of a variety of neurodegenerative disorders; although there is limited information on the neuroprotective properties of alkaloids from various tropical green leafy vegetables with neuroprotective potentials. As a result, this study examined the cholinesterase inhibitory activity and antioxidant potential of alkaloid extracts from the leaves of African Jointfir (G. africanum) and Editan (L. africana). Standard solvent extraction techniques were used to prepare alkaloid extracts. After that, these extracts were characterized using high‐performance liquid chromatography. In vitro acetylcholinesterase inhibition assay for the extracts was also carried out. Subsequently, the alkaloid extracts were included in the diets of these flies (2 and 10 μg/g) for 7 days. Thereafter, treated fly homogenates were assayed for cholinesterase, monoamine oxidase, and antioxidant enzymes (specifically, glutathione‐S‐transferase catalase, and superoxide dismutase) activities, in addition, thiobarbituric acid reactive substance, reactive oxygen species, and total thiol contents. The extracts showed considerable anticholinesterase, antioxidant, and antimonoamine oxidase capabilities, according to the study's findings. Also, HPLC characterization revealed that desulphosinigrin (597,000 ng/100 g) and atropine (44,200 ng/100 g) are the predominating phytochemicals in Editan and African Jointfir respectively. These extracts could serve as potential sources of nutraceuticals with neuroprotective properties which can be used in the treatment/management of Alzheimer's disease. This study reveals that alkaloid extracts from Editan (Lasianthera africana) and African Jointfir (Gnetum africanum) could possess antioxidant and anticholinesterase activities in Drosophila melanogaster. Desulphosinigrin and atropine were revealed through high‐performance liquid chromatography to be the predominating plant chemicals in L. africana and G. africanum, respectively. Alkaloid extracts from both plants exhibited outstanding lipid peroxidative ability.

Dataset Information

Wild African Drosophila melanogaster Are Seasonal Specialists on Marula Fruit.

Publications

Wild African Drosophila melanogaster Are Seasonal Specialists on Marula Fruit.

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