The bloodstream form ofTrypanosoma bruceidisplays non-canonical gluconeogenesis

Trypanosoma bruceiis the causative agent of the Human and Animal African Trypanosomiases. Mammalian stage parasites infect the bloodstream, central nervous system, but also skin, adipose tissue or lungs. They rely on ATP produced in glycolysis, consuming large amounts of glucose which is readily available in mammalian tissues. In addition to glucose, glycerol can be utilised as a carbon and ATP source and also as a substrate for gluconeogenesis. The physiological relevance of glycerol-fed gluconeogenesis for mammalian-infective trypanosome life-cycle stages, however, remins elusive. Loss of the canonical gluconeogenic enzyme, fructose-1,6-bisphosphatase, does not abolish the process hence at least one other enzyme must participate in gluconeogenesis in trypanosomes. Using a combination of CRISPR/Cas9 gene editing and RNA interference, we generated mutants for four enzymes potentially capable of contributing to gluconeogenesis: fructose-1,6-bisphoshatase, sedoheptulose-1,7-bisphosphatase, phosphofructokinase, transaldolase, alone or in various combinations. Metabolomic analyses revealed that flux through gluconeogenesis was maintained irrespective of which of these genes were lost. Our data renders unlikely a previously hypothesised role of a reverse phosphofructokinase reaction in gluconeogenesis and precludes the participation of a novel biochemical pathway involving transaldolase in the process. Sustained metabolic flux in gluconeogenesis in our mutants, including in a triple-null strain, provides new insights into gluconeogenesis and the pentose phosphate pathway, and improves the current understanding of carbon metabolism of the mammalian-infective stages ofT. brucei.