MappingWolbachiadistributions in the adultDrosophilabrain

Abstract

SummaryThe maternally inherited bacterium Wolbachia infects the germline of most arthropod species. Using Drosophila simulans and D. melanogaster, we demonstrate that localization of Wolbachia to the fat bodies and adult brain is likely also a conserved feature of Wolbachia infection. Examination of three Wolbachia strains (WMel, WRiv, WPop) revealed that the bacteria preferentially concentrate in the central brain with low titres in the optic lobes. Distribution within regions of the central brain is largely determined by the Wolbachia strain, while the titre is influenced by both, the host species and the bacteria strain. In neurons of the central brain and ventral nerve cord, Wolbachia preferentially localizes to the neuronal cell bodies but not to axons. All examined Wolbachia strains are present intracellularly or in extracellular clusters, with the pathogenic W Pop strain exhibiting the largest and most abundant clusters. We also discovered that 16 of 40 lines from the Drosophila Genetic Reference Panel are Wolbachia infected. Direct comparison of Wolbachia infected and cured lines from this panel reveals that differences in physiological traits (chill coma recovery, starvation, longevity) are partially due to host line influences. In addition, a tetracycline-induced increase in Drosophila longevity was detected many generations after treatment.

Drosophila melanogaster brain invasion: pathogenic Wolbachia in central nervous system of the fly

“…Three layers of membranes could be easily recognized under electron microscope and we used it as an identification feature. The Wolbachia strain w MelPop was detected in all regions of D. melanogaster brain with the highest concentration in the central brain and cells surrounding subesophageal ganglion that is in agreement with data obtained with the help of immunofluorescent analysis (Albertson et al ., ). The majority of cells from the optic lobes were free of bacteria.…”

“…The extreme pathogenicity of this strain in Drosophila was directly correlated with alterations in the symbiont's own density control and not with the host genetic background (McGraw et al ., ). Recently it was shown that the presence of natural variants of Wolbachia in nervous tissues is a conserved feature of this endosymbiont in a wide range of insect host species, albeit at lower densities (Dobson et al ., ; Albertson et al ., ; Albertson et al ., ). This discovery opened a broad field of undisclosed Wolbachia somatic life to study.…”

Behavioral decline and premature lethality upon pan-neuronal ferritin overexpression in Drosophila infected with a virulent form of Wolbachia

“…Our study provided evidence that w MelPop, or a w MelPop-like strain, causes neuronal death, likely by inducing the apoptotic pathway in infected brains, with apoptosis seen also in the optic lobes, which generally were found to harbor significantly less bacteria (Albertson et al, 2013; Strunov et al, 2013). Ferritin overexpression, which likely results in depletion of readily bioavailable iron (Gutierrez et al, 2013), conferred no apparent protection to infected flies, but instead further decreased their shortened lifespan due to Wolbachia infection ( Figure 3B ).…”

“…Intriguingly, a small genomic region encoding 24 bacterial genes (out of a total of 1,111 annotated in the species) was either triplicated or absent in the pathogenic strains (Woolfit et al, 2013). Finally, two recent imaging studies documented in anatomical detail the presence of w MelPop in the fly brain (Albertson et al, 2013; Strunov et al, 2013). …”

Wolbachia Influences the Production of Octopamine and Affects Drosophila Male Aggression

“…Thus, male reproductive success is a key component of how Wolbachia invades insect populations. Evolutionary theory predicts that Wolbachia should impose relatively few, if any, detrimental effects upon male mating behaviors, including male aggression; yet all strains that infect D. melanogaster are known to infect neural tissue (33).…”