Identification and distribution of dietary precursors of the Drosophila visual pigment chromophore: analysis of carotenoids in wild type and ninaD mutants by HPLC

A dietary source of retinoid or carotenoid has been shown to be necessary f or the biosynthesis of functional visual pigment in flies. In the present s tudy, the larvae or adults of Drosophila melanogaster were administered spe cific carotenoid-containing diets and high performance liquid chromatograph y was used to identify and quantify the carotenoids in extracts of wild typ e and ninaD visual mutant flies. When beta-carotene was fed to larvae, wild type flies were shown to hydroxylate this molecule and to accumulate zeaxa nthin and a small amount of beta-cryptoxanthin. Zeaxanthin content was foun d to increase throughout development and was a major carotenoid peak detect ed in the adult fly. Carotenoids were twice as effective at mediating zeaxa nthin accumulation when provided to larvae versus adults. In the ninaD muta nt, zeaxanthin content was shown to be specifically and significantly alter ed compared to wild type, and was ineffective at mediating visual pigment s ynthesis when provided to both larval and adult mutant flies. It is propose d that zeaxanthin is the larval storage form for subsequent visual pigment chromophore biosynthesis during pupation, that zeaxanthin or beta-crytoxant hin is the immediate precursor for light-independent chromophore synthesis in the adult, and that the ninaD mutant is defective in this pathway. (C) 1 998 Elsevier Science Ltd. All rights reserved.