Abstract
BackgroundTrypanosoma brucei subspecies infect humans and animals in sub-Saharan Africa. This early diverging eukaryote shows many novel features in basic biological processes, including the use of polycistronic transcription to generate all protein-coding mRNAs. Therefore we hypothesized that translational control provides a means to tune gene expression during parasite development in mammalian and fly hosts.ResultsWe used ribosome profiling to examine genome-wide protein synthesis in animal-derived slender bloodstream forms and cultured procyclic (insect midgut) forms. About one-third of all CDSs showed statistically significant regulation of protein production between the two stages. Of these, more than two-thirds showed a change in translation efficiency, but few appeared to be controlled by this alone. Ribosomal proteins were translated poorly, especially in animal-derived parasites. A disproportionate number of metabolic enzymes were up-regulated at the mRNA level in procyclic forms, as were variant surface glycoproteins in bloodstream forms. Comparison with cultured bloodstream forms from another strain revealed stage-specific changes in gene expression that transcend strain and growth conditions. Genes with upstream ORFs had lower mean translation efficiency, but no evidence was found for involvement of uORFs in stage-regulation.ConclusionsRibosome profiling revealed that differences in the production of specific proteins in T. brucei bloodstream and procyclic forms are more extensive than predicted by analysis of mRNA abundance. While in vivo and in vitro derived bloodstream forms from different strains are more similar to one another than to procyclic forms, they showed many differences at both the mRNA and protein production level.Electronic supplementary materialThe online version of this article (doi:10.1186/1471-2164-15-911) contains supplementary material, which is available to authorized users.
Highlights
Trypanosoma brucei subspecies infect humans and animals in sub-Saharan Africa
Our primary focus was on two rapidly proliferating life cycle stages (PCF and slender BF (slBF)) that are readily available for the pleiomorphic T. brucei strain 927, which has retained the ability to differentiate and has the most complete genome sequence available
We examined cultured bloodstream forms (BF) from another often-used strain, T. brucei 427
Summary
Trypanosoma brucei subspecies infect humans and animals in sub-Saharan Africa. This early diverging eukaryote shows many novel features in basic biological processes, including the use of polycistronic transcription to generate all protein-coding mRNAs. we hypothesized that translational control provides a means to tune gene expression during parasite development in mammalian and fly hosts. A limited number of individual genes have been shown to be developmentally regulated at the level of translation [15,16,17,18] and numerous examples of discrepancies between stage-specific changes in mRNA and protein level exist. A recent study has noted some changes in the association of mRNAs with polysomes in developing mammalian bloodstream forms (BF) [19] and initial work suggests that the changes in translation efficiency occur between cultured BF and cultured insect stages [20]. The work presented here aimed to define the role of translational control in modulating differences in gene expression during parasite development
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