Dataset Information

The Genetics of Resistance to Morinda Fruit Toxin During the Postembryonic Stages in Drosophila sechellia.

ABSTRACT: Although a great deal has been learned regarding the genetic changes that give rise to adaptation in bacteria and yeast, an understanding of how new complex traits arise in multicellular organisms is far less complete. Many phytophagous insect species are ecological specialists that have adapted to utilize a single host plant. Drosophila sechellia is a specialist that utilizes the ripe fruit of Morinda citrifolia, which is toxic to its sibling species, D. simulans. Here we apply multiplexed shotgun genotyping and QTL analysis to examine the genetic basis of resistance to M. citrifolia fruit toxin in interspecific hybrids. We identify a locus of large effect on the third chromosome (QTL-IIIsima) in the D. simulans backcross that was not detected in previous analyses. We also identify a highly significant QTL of large effect on the X chromosome, QTL-Xsim. Additional smaller-effect loci were also identified in the D. simulans and D. sechellia backcrosses. We did not detect significant epistasis between loci. Instead, our analysis reveals large and smaller-effect loci that contribute to M. citrifolia resistance additively. The additive effect of each locus suggests that partial resistance to lower levels of M. citrifolia toxin could be passed through introgression from D. sechellia to D. simulans in nature. The identification of the major effect loci, QTL-IIIsima and QTL-Xsim, is an important step toward identifying the molecular basis of adaptation in a multicellular organism.

SUBMITTER: Huang Y

PROVIDER: S-EPMC4592979 | biostudies-literature | 2015 Jul

REPOSITORIES: biostudies-literature

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The Genetics of Resistance to Morinda Fruit Toxin During the Postembryonic Stages in Drosophila sechellia.

Huang Yan Y Erezyilmaz Deniz D

G3 (Bethesda, Md.) 20150729 10

Although a great deal has been learned regarding the genetic changes that give rise to adaptation in bacteria and yeast, an understanding of how new complex traits arise in multicellular organisms is far less complete. Many phytophagous insect species are ecological specialists that have adapted to utilize a single host plant. Drosophila sechellia is a specialist that utilizes the ripe fruit of Morinda citrifolia, which is toxic to its sibling species, D. simulans. Here we apply multiplexed shot ...[more]

PMID: 26224784

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Project description:The underlying genetic basis of adaptive phenotypic changes are generally poorly understood, yet a growing number of case studies are beginning to shed light on important questions about the molecular nature and pleiotropy of such changes. We use Drosophila sechellia, a dietary specialist fruit fly that has evolved to specialize on a single toxic host plant: Morinda citrifolia, as a model for adaptive phenotypic change and seek to determine the genetic basis of traits associated with host specialization in this species. The fruit of M. citrifolia is toxic to other Drosophilids, primarily due to high levels of the defense chemical octanoic acid (OA) yet D. sechellia has evolved resistance to OA. Our prior work identified three Osiris family genes that reside in a fine-mapped QTL for OA resistance: Osiris 6 (Osi6), Osi7, and Osi8, that can alter OA resistance in adult D. melanogaster when knocked-down with RNA interference (RNAi) suggesting they may contribute to OA resistance in D. sechellia. Genetic mapping identified overlapping genomic regions involved in larval and adult OA resistance in D. sechellia, yet it remains unknown whether Osiris genes contribute to resistance in both life stages. Furthermore, because multiple genomic regions contribute to OA resistance, we aim to identify other gene(s) involved in this adaptation. Here, we identify candidate larval OA resistance genes using RNA-sequencing to measure genome-wide differential gene expression in D. sechellia larvae after exposure to OA and functionally test identified genes for a role in OA resistance. We then test the Osiris genes previously shown to alter adult OA resistance for effects on OA resistance in larvae. While the genes identified by RNA-seq we tested in larvae thus far do not influence OA resistance, we found that Osi8 knockdown decreased OA resistance in D. melanogaster larvae. These data suggest that evolved changes in Osi8 could impact OA resistance in multiple life stages while Osi6 and Osi7 may only impact adult resistance to OA.

Dataset Information

The Genetics of Resistance to Morinda Fruit Toxin During the Postembryonic Stages in Drosophila sechellia.

Publications

The Genetics of Resistance to Morinda Fruit Toxin During the Postembryonic Stages in Drosophila sechellia.

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