Potential association between tsetse fly and its endosymbionts in b-vitamins biosynthesis

Abstract

Tsetse flies are the cyclical vectors of African trypanosomes, flagellated protozoa parasites that cause sleeping sickness in man and nagana in cattle, diseases collectively known as African trypanosomiasis. Vector reduction and chemotherapy are the main strategies for controlling trypanosomiasis but their limitations necessitate improvement of current and/or development of novel methods. Tsetse has three maternally transmitted bacterial endosymbionts namely Wigglesworthia, Sodalis and Wolbachia which are potential targets in developing paratransgenesis control approaches. Wigglesworthia is thought to provide B-vitamins to its host, but its B-vitamins biosynthesis pathways are incomplete while those for tsetse remain unknown. Using the recently published Glossina morsitans morsitans genome, bioinformatics approach was applied to annotate tsetse B-vitamins and cofactors biosynthesis enzymes. Homology based searches, protein domain architecture interrogations, comparative and RNA seq analyses, polymerase chain reaction (PCR) amplification and sequencing were performed for annotation and interrogation of possible tsetse-endosymbiont interaction. Thirty four genes encode 26 enzymes involved in biosynthesis of B-vitamins namely thiamine, riboflavin, niacin, folate, pantothenate, pyridoxine and their resultant cofactors. Vitamins biosynthesis pathways are incomplete, a phenomenon also observed in insects and humans. However, cofactors biosynthesis pathways are complete in all the organisms analyzed. Notably, integration of tsetse-endosymbionts systems gives complete or near complete pathways suggesting potential association. Moreover, expression of these enzymes depends on availability of endosymbionts, and presence of vitamin transporters in both organisms support association at biochemical level. This association can be through integrated biosynthetic pathways that involve import/export transporters of metabolic intermediates and sharing of final products for cofactor biosynthesis. Therefore, one of the possible bases of the symbiotic association of tsetse and its endosymbinots is B-vitamins biosynthesis.