Differential expression of mitochondrial genes between life cycle stages of Trypanosoma brucei.

The mitochondrial respiratory system is differentially produced during the life cycle of the parasitic protozoan, Trypanosoma brucei. We have found 14 transcripts that are derived from a maxicircle (mitochondrial DNA) region that contains sequences homologous to cytochrome c oxidase subunits I and II, unassigned reading frame 1 from mitochondrial DNA of other organisms, and two other open reading frames. Ten of these transcripts occur as pairs that differ in size by approximately equal to 200 nucleotides. While most of these transcripts occur in both life cycle forms, four transcripts are differentially expressed. Of these, two are more abundant in bloodstream forms, one is more abundant in procyclic forms, and one is present in procyclic but not bloodstream forms. These results indicate that the differential production of the mitochondrial respiratory system in T. brucei entails regulation of mitochondrial transcriptional and/or posttranscriptional processes.