Diet-induced changes in titer support a discrete response of Wolbachia-associated plastic recombination in Drosophila melanogaster

Abstract

Plastic recombination in Drosophila melanogaster has been associated with a variety of extrinsic and intrinsic factors such as temperature, starvation, and parasite infection. The bacterial endosymbiont Wolbachia pipientis has also been associated with plastic recombination in D. melanogaster. Wolbachia infection is pervasive in arthropods and this infection induces a variety of phenotypes in its hosts, the strength of which can depend on bacterial titer. Here we test the hypothesis that the magnitude of Wolbachia-associated plastic recombination in D. melanogaster depends on titer. To manipulate titer, we raised Wolbachia-infected and uninfected flies on diets that have previously been shown to increase or decrease Wolbachia titer relative to controls. We measured recombination in treated and control individuals using a standard backcrossing scheme with two X-linked visible markers. Our results recapitulate previous findings that Wolbachia infection is associated with increased recombination rate across the yellow-vermillion interval of the X chromosome. Our data show no significant effect of diet or diet by Wolbachia interactions on recombination, suggesting that diet-induced changes in Wolbachia titer have no effect on the magnitude of plastic recombination. These findings represent one of the first steps toward investigating Wolbachia-associated plastic recombination and demonstrate that the phenotype is a discrete response rather than a continuous one.

Ovarian transcriptional response to Wolbachia infection in D. melanogaster in the context of between-genotype variation in gene expression

“…In the Drosophila early ovarian transcriptome, genomic regions with higher rates of transcription also have higher rates of recombination ( Adrian and Comeron 2012 ). Since Wolbachia infection leads to increased recombination at certain genomic regions ( Mostoufi and Singh 2022 ) ( Singh 2019 ; Bryant and Newton 2020 ), we tested whether infection may also be associated with altered levels of transcription at certain genomic regions. To do so, we performed runs test for randomness ( Bradley 1968 ) to determine whether the binary sequence of genes that are categorized as differentially expressed is random across the genome.…”

“…If the observed increase in recombination at the X-chromosome locus associated with Wolbachia infection ( Singh 2019 ; Mostoufi and Singh 2022 ) was due to increased transcription in this region, we expect to observe higher numbers of upregulated genes at this region. We instead observe approximately equal numbers of upregulated and downregulated genes at this region.…”

“…It has recently been shown that Wolbachia infection also increases the recombination fraction ( Singh 2019 ; Bryant and Newton 2020 ; Mostoufi and Singh 2022 ). If Wolbachia -associated plastic recombination is driven by changes in gene expression, then genes that are differentially expressed in response to infection may point to the molecular genetic mechanisms underlying increased recombination in Wolbachia -infected flies.…”

“…Since the X-chromosome interval was previously found to exhibit increased recombination in Wolbachia -infected flies ( Singh 2019 ; Mostoufi and Singh 2022 ), we compared our differentially expressed genes to a list of 111 genes significantly associated with variation in recombination at the X-chromosome locus as determined by a GWAS ( Hunter et al 2016 ). We found 10 genes in common between these 2 studies: Pka-C3 , px , ND-23 , oat , DAAM , Tgi , dpr6 , spri , Msp3000 (batch 1), and CG11200 (batch 2).…”

Food provisioning to Pardosa spiders decreases the levels of tissue-resident endosymbiotic bacteria

“…Whether differences in prey type and quantity affect tissue-resident spider microbiome is unclear. Data from other invertebrates suggest that tissue-resident endosymbiotic organisms respond swiftly to diet-induced changes 13 – 16 . However, altered quantity of endosymbiotic organisms, like Wolbachia , has often only limited or no effect on the nutrition, fecundity or viability of their invertebrate hosts 13 , 17 .…”