CONTROL OF DROSOPHILA OPSIN GENE-EXPRESSION BY CAROTENOIDS AND RETINOIC ACID - NORTHERN AND WESTERN ANALYSES

In the fly, thorough retinoid deprivation is possible, to optimize inv estigation of the effects of vitamin A metabolites and retinoic acid ( RA) on visual development. Retinoids had been found to control fly ops in gene transcription, though this finding was contested. Northern blo ts on Drosophila heads showed that mRNA of Rh1 (the predominant rhodop sin) was high in vitamin A replete controls, very low in deprived flie s, and increased upon feeding carrot juice to deprived flies as early as I hr. Expression of the ribosomal protein 49 [rp49] gene (the contr ol) was equal both in deprivation and in replacement. Recovery of Rh1 protein upon such carotenoid replacement followed, barely detectable o n Western blots at 4 hr but conspicuous by 8 hr. Alternative chromopho re deprivation with yeast-glucose food yielded flies with opsin mRNA o n Northerns but not rhodopsin, as demonstrated by Western blots, spect rophotometry and the electroretinogram (ERG). Rh1's mRNA but not Rh1 p rotein resulted from rearing flies from egg to adult on the otherwise deprivational medium supplemented with RA or beef brain-heart infusion . By comparing results from these different media it was concluded tha t: [1] deprivation and replacement affect opsin gene transcription; an d [2] contradictory conclusions were from chromophore deprivation whic h does not eliminate all retinoid dependent factors which could affect the opsin promoter. Preliminary evidence shows that carotenoid depriv ation decreases two proteins relevant to visual function: [1] phosphol ipase C (PLC); and [2] Drosophila retinoid binding protein (DRBP). (C) 1996 Academic Press Limited