Molecular characterization of tsetse’s proboscis and its response to Trypanosoma congolense infection

Abstract

Tsetse flies (Glossina spp.) transmit parasitic African trypanosomes (Trypanosoma spp.), including Trypanosoma congolense, which causes animal African trypanosomiasis (AAT). AAT detrimentally affects agricultural activities in sub-Saharan Africa and has negative impacts on the livelihood and nutrient availability for the affected communities. After tsetse ingests an infectious blood meal, T. congolense sequentially colonizes the fly’s gut and proboscis (PB) organs before being transmitted to new mammalian hosts during subsequent feedings. Despite the importance of PB in blood feeding and disease transmission, little is known about its molecular composition, function and response to trypanosome infection. To bridge this gap, we used RNA-seq analysis to determine its molecular characteristics and responses to trypanosome infection. By comparing the PB transcriptome to whole head and midgut transcriptomes, we identified 668 PB-enriched transcripts that encoded proteins associated with muscle tissue, organ development, chemosensation and chitin-cuticle structure development. Moreover, transcripts encoding putative mechanoreceptors that monitor blood flow during tsetse feeding and interact with trypanosomes were also expressed in the PB. Microscopic analysis of the PB revealed cellular structures associated with muscles and cells. Infection with T. congolense resulted in increased and decreased expression of 38 and 88 transcripts, respectively. Twelve of these differentially expressed transcripts were PB-enriched. Among the transcripts induced upon infection were those encoding putative proteins associated with cell division function(s), suggesting enhanced tissue renewal, while those suppressed were associated with metabolic processes, extracellular matrix and ATP-binding as well as immunity. These results suggest that PB is a muscular organ with chemosensory and mechanosensory capabilities. The mechanoreceptors may be point of PB-trypanosomes interactions. T. congolense infection resulted in reduced metabolic and immune capacity of the PB. The molecular knowledge on the composition and putative functions of PB forms the foundation to identify new targets to disrupt tsetse’s ability to feed and parasite transmission.

Expression profiling of Trypanosoma congolense genes during development in the tsetse fly vector Glossina morsitans morsitans

“…Dissections of cardia for T. congolense infection analyses were microscopically conducted in PSG buffer (pH 8.0) using Zeiss Axiostar Plus light microscope (Carl Zeiss Light Microscopy, Gottingen) at ×400 magnification. Two biological replicates of infected probosces (consisting of 130 probosces each) from a recent study were used [ 30 ]. Infected cardia were immediately placed in TRIzol (Thermo Fisher Scientific Inc., CA, USA).…”

“…For the generation of these cDNA libraries, 900 ng of high quality (RNA integrity number > 7.0) total RNA samples was used. The Sequence Read Archive number at NCBI of infected cardia is SRP093558 and that of infected probosces is PRJNA354110 [ 30 ].…”

Insect Mouthpart Transcriptome Unveils Extension of Cuticular Protein Repertoire and Complex Organization

“…Among cuticular structures, the most studied are the bulky surface covers layered over the ectodermal epithelia of insects, but some represent more specialized regions, mostly associated with the segmental organization of insects (metameric appendages, legs, wings). The biochemistry of the most specialized cuticular structures, those of head appendages such as the antennae and mouthparts, has scarcely been studied (Zhao et al, 2018;Awuoche et al, 2017;Zhou et al, 2014;Oliveira et al, 2017). A single recent publication involving mouthpart transcriptomics did not address the time and organs strictly responsible for cuticular biogenesis stricto sensu (tsetse fly proboscis organ) and was not focused on biomaterial characterization (Awuoche et al, 2017).…”

The composition and abundance of bacterial communities residing in the gut of Glossina palpalis palpalis captured in two sites of southern Cameroon

“…Despite the differences between T. congolense and T. brucei regarding their hosts, vectors and virulence (reviewed in [12, 14, 15]), these pathogens share a number of biological characteristics such as the need to infect two consecutive and different hosts (e.g. a tsetse fly followed by a mammal) in order to complete their life-cycle.…”