“Wigglesworthia morsitans” Folate (Vitamin B9) Biosynthesis Contributes to Tsetse Host Fitness

Abstract

ABSTRACTClosely related ancient endosymbionts may retain minor genomic distinctions through evolutionary time, yet the biological relevance of these small pockets of unique loci remains unknown. The tsetse fly (Diptera: Glossinidae), the sole vector of lethal African trypanosomes (Trypanosomaspp.), maintains an ancient and obligate mutualism with species belonging to the gammaproteobacteriumWigglesworthia. Extensive concordant evolution with associatedWigglesworthiaspecies has occurred through tsetse species radiation. Accordingly, the retention of unique symbiont loci betweenWigglesworthiagenomes may prove instrumental toward host species-specific biological traits. Genome distinctions between “Wigglesworthiamorsitans” (harbored withinGlossina morsitansbacteriomes) and the basal speciesWigglesworthia glossinidia(harbored withinGlossina brevipalpisbacteriomes) include the retention of chorismate and downstream folate (vitamin B9) biosynthesis capabilities, contributing to distinct symbiont metabolomes. Here, we demonstrate that theseW. morsitanspathways remain functionally intact, with folate likely being systemically disseminated through a synchronously expressed tsetse folate transporter within bacteriomes. The folate produced byW. morsitansis demonstrated to be pivotal forG. morsitanssexual maturation and reproduction. Modest differences between ancient symbiont genomes may still play key roles in the evolution of their host species, particularly if loci are involved in shaping host physiology and ecology. Enhanced knowledge of theWigglesworthia-tsetse mutualism may also provide novel and specific avenues for vector control.