DEVELOPMENTAL REGULATION OF MITOCHONDRIAL BIOGENESIS IN TRYPANOSOMA-BRUCEI

The metabolism of Trypanosoma brucei undergoes a significant change as the parasite differentiates from the mammalian bloodstream form to th e form found in the tse-tse fly vector. Because the mitochondria of bl oodstream form cells lack cytochromes and several key citric acid cycl e enzymes, the metabolism of these cells is mostly limited to glycolys is. The reducing equivalents generated by this process are passed to o xygen by a plantlike alternative oxidase. As cells differentiate to th e insect form, they begin to oxidatively metabolize proline. The mitoc hondria of insect form cells contain functional, cytochrome-mediated e lectron transport chains and have complete complements of citric acid cycle enzymes. Although the characterization is far from complete, the nuclear and mitochondrial genes involved in the expression of these m itochondrial functions appear to be developmentally regulated at postt ranscriptional and posttranslational levels. This review outlines some of the molecular processes that are associated with the developmental regulation of mitochondrial biogenesis and suggests some possible mec hanisms of regulation.