Differential mitochondrial gene expression between slender and stumpy bloodforms of Trypanosoma brucei.

Bloodforms of Trypanosoma brucei lack complete cytochrome and Krebs cycle systems but a fully functional mitochondrial respiratory system is elaborated upon differentiation to procyclics. We previously found differential expression of some mitochondrial genes, at the level of transcript abundance, between these two life cycle stages. We report here that mitochondrial genes are also differentially expressed between the two morphological types of bloodforms. Some transcripts that are more abundant in procyclics than slender bloodforms are intermediate in abundance in stumpy bloodforms. Most major mitochondrial transcripts are more abundant in stumpy than slender bloodform RNA; some are also more abundant than in procyclic RNA. Transcripts from protein coding genes are increased in abundance to varying degrees. Treatment with difluoromethylornithine, which induces a stumpy morphology, produces transcript abundance patterns similar to those in naturally occurring stumpy bloodforms. Stumpy bloodforms also have a decrease in tubulin transcript abundance, consistent with their nondividing character and smaller flagellum. These studies suggest that molecular events associated with mitochondrial development during the differentiation from bloodforms to procyclics can be initiated in the bloodstream, and that maxicircle transcript abundances are individually modulated during the life cycle.