Abstract:
Tsetse fly is a primary vector of Human African Trypanosomiasis and Animal African
Trypanosomiasis. Tsetse fly exploits chemical cues from the environment to
distinguish a non- from suitable hosts. Genes in tsetse fly antennae code for proteins
and receptors that directly or indirectly mediate chemoreception. While
chemoreception-associated genes have been annotated, antennal genes in the Glossina.
m. morsitans genome with important functions have not been characterized. Antennaespecific
raw reads from adult flies exposed to four treatments, namely, fed, unfedexposed
to ε-nonalactone attractant, unfed-exposed to δ-nonalactone repellant and
unfed-exposed to paraffin diluent (control) were mapped onto G. m. morsitans geneset.
Reads that did not map were isolated and de novo assembled into transcripts.
Protein-coding gene regions associated with these transcripts were predicted,
annotated and curated as partial/complete genes. Annotated putative
orthologs/homologs for these genes in Drosophila melanogaster (Dm), Musca
domestica (Md) or Anopheles gambiae (Ag) genomes were identified. Finally,
differential expression of the novel or existing genes in relation to odor exposures
relative to no-odor control (unfed flies) were assessed and expression of existing genes
quantified through qPCR. Results showed that 45.21% of the sequenced reads did not
map to the gene set. These reads assembled into 72,428 unique transcripts that yielded
592 genes among which 202 were novel and 390 were improvements of existing genes
in the G. m. morsitans genome. Among the novel genes, 94 had orthologs in Dm, Md
or Ag and 88 had homologs in UniProt databases. These orthologs were putatively
associated with non-canonical olfactory roles, thus providing insight into their specific
roles in antennal physiological processes. A novel gene (GMOY014237.R1396) and
15 existing genes were differentially expressed in response to the attractant or
repellent. Differential expression through qPCR analysis unveiled three antennal
transcripts, i.e., the coat protein epsilon, cyclin-dependent kinase and odorant receptor
45, all three up-regulated in response to the attractant. Novel genes sequences were
adopted by VectorBase, updating the existing G. m. morsitans annotations. This study
identified 108 potentially tsetse fly-specific antennal genes. The novel antennal genes
could be used as baseline data in studies of other tsetse fly species, and with an
orientation towards attraction and or repellency in their control.
