Tryptophan metabolism in tsetse flies and the consequences of its derangement

Abstract

Literature comparing salmon and wild type Glossina morsitans morsitans and that comparing tan and wild type Glossina palpalis palpalis is reviewed. New information is presented on behaviour and biochemistry of salmon and wild type G. m. morsitans. The eye color mutants result from two lesions in the tryptophan to xanthommatin pathway: lack of tryptophan oxygenase in G. m morsitans and failure to produce or retain xanthommatin in eyes (but not in testes) of G. p. palpalis. The salmon allele in G. m. morsitans is pleiotropic and profoundly affects many aspects of fly biology including longevity, reproductive capacity, vision, vectorial capacity and duration of flight, but not circadian rhythms. The tan allele in G. p. palpalis has little effect upon the biology of flies under laboratory conditions, except that tan flies appear less active than normal. Adult tsetse flies metabolize tryptophan to kynurenine which is excreted; fluctuations in activities of the enzymes producing kynurenine suggest this pathway is under metabolic control.

Identification of midgut proteins that are differentially expressed in trypanosome-susceptible and normal tsetse flies (Glossina morsitans morsitans)

“…These findings extend the range of known pleiotropic effects of the salmon allele in G. m. morsitans. These effects were already known to include adverse effects on puparial development and survival, adult longevity, reproductive capacity, vision and flight duration (Gooding, 1979;Gooding and Rolseth, 1987) and to enhance susceptibility to, and maturation of, pathogenic trypanosomes (Makumyaviri et al, 1984;Distelmans et al, 1985). The present study adds a significant list of molecular perturbations to the only previously known molecular effect, namely the absence or inactivity of tryptophan oxygenase which is the lesion causing the salmon-colored eyes (Gooding and Rolseth, 1984).…”

“…The G. m. morsitans salmon eye color mutant (Gooding, 1979) lacks a functional tryptophan oxygenase causing a lesion in the tryptophan to xanthomatin (eye pigment) biosynthetic pathway (Gooding and Rolseth, 1984). The salmon allele is pleiotropic and affects many aspects of tsetse biology including longevity, reproduction and vector competence (Gooding and Rolseth, 1987). Most importantly, wild type and salmon flies differ in susceptibility to infection by African trypanosomes.…”