Drosophila female fertility and juvenile hormone metabolism depends on the type of Wolbachia infection

Abstract

Maternally inherited intracellular bacteria Wolbachia cause both parasitic and mutualistic effects on their numerous insect hosts that include manipulating the host reproductive system in order to increase the bacteria spreading in a host population, and increasing the host fitness. Here we demonstrate that the type of Wolbachia infection determines the effect on Drosophila melanogaster egg production as a proxy for fecundity and metabolism of juvenile hormone (JH), which acts as gonadotropin in adult insects. For this study we used six D. melanogaster lineages carrying the nuclear background of interbred Bi90 lineage and cytoplasmic backgrounds with Wolbachia of different genotype variants or without it. wMelCS genotype of Wolbachia decreases the egg production in the infected D. melanogaster females in the beginning of oviposion and increases it later (since the sixth day after eclosion), wMelPop Wolbachia strain causes the opposite effect, while wMel, wMel2 and wMel4 genotypes of Wolbachia do not show any effect on these traits compared to uninfected Bi90 D. melanogaster females. The intensity of JH catabolism negatively correlates with the fecundity level in the flies carrying both wMelCS and wMelPop Wolbachia. The JH catabolism in females infected with genotypes of wMel group does not differ from that in uninfected females. The effects of wMelCS and wMelPop infection on egg production can be leveled by the modulation of JH titre (via precocene/JH treatment of the flies). Thus, at least one of the mechanisms, promoting the effect of Wolbachia on D. melanogaster female fecundity, is mediated by JH.