The Genetic Basis of Drosophila sechellia's Resistance to a Host Plant Toxin

Abstract

Unlike its close relatives, Drosophila sechellia is resistant to the toxic effects of the fruit of its host plant, Morinda citrifolia. Using 15 genetic markers, I analyze the genetic basis of D. sechellia's resistance to this fruit's primary toxin, octanoic acid. D. sechellia's resistance is dominant in F1 hybrids between it and its sister species D. simulans. All chromosomes, except the Y and the dot fourth, carry genes affecting resistance. The third chromosome has the greatest effect and carries at least two factors. The X chromosome has an intermediate effect and harbors at least two genes, whereas the second chromosome carries at least one gene of weak effect. Thus, at least five loci are involved in this adaptation. However, I also identified large chromosome regions having no effect on resistance, suggesting that D. sechellia's resistance is neither very simple nor highly polygenic. Instead, resistance appears to have an oligogenic basis. D. sechellia's resistance to its host may contribute to ecological isolation between it and D. simulans.

Compatibility between snails and schistosomes: insights from new genetic resources, comparative genomics, and genetic mapping

“…The clustering of QTLs in the centromeric and pericentromeric regions has also been observed in many plants, such as root-related traits of wheat 50 , grain weight of rice and wheat 51 , 52 , and head blight resistance of wheat 53 . In Drosophila , a QTL affecting knockdown resistance to high temperature in D. melanogaster and a QTL for D. sechellia resistance to toxins were found to be strongly associated with the pericentromeric regions of the third chromosome 54 , 55 . In B. glabrata , two resistance loci, GRC/SOD (in LG6) and RADres (in LG10), were found in a low-recombining centromeric/pericentromeric region 24 , 25 .…”

Helicoverpa armigera miR-2055 regulates lipid metabolism via fatty acid synthase expression

“…In order to maximize the fitness to certain hosts, many plant-eating insects even change their genetic background. Drosophila sechellia has evolved to tolerate the fruit of Morinda citrifolia , which is toxic to other members of the melanogaster species [ 46 , 47 ]. Later genetic analysis revealed that a 45 bp deletion (relative to D. melanogaster ) in the open reading frame of catsup , one of the negative regulators in the production of L-DOPA, enables D. sechellia to produce larger eggs and drives them to adapt the chemical compounds of M. citrifolia [ 48 , 49 ].…”

Evolutionary neuroecology of olfactory‐mediated sexual communication and host specialization in Drosophila – a review

“…The extreme specialism that D. sechellia has evolved compared to its close cousins did not only result in an increased metabolic tolerance of noni fruit toxins (R'Kha et al, 1991; Jones, 1998), but also in changes in courtship and mate choice (Cobb et al, 1989; Coyne, 1992), oviposition (Moreteau et al, 1994; Amlou et al, 1998), and pupariation site selection (Erezyilmaz & Stern, 2013). Recently, these shifts were shown to be correlated with changes at the periphery of the fly’s olfactory system, i.e., whereas the odorant receptor OR22b is lost, the flies exhibit an increased number of neurons expressing OR22a (Auer et al, 2020).…”