A Physiological Study of the Vermilion Eye Color Mutants of Drosophila Melanogaster.

HE vermilion eye color mutant Drosophila melanogaster was one of the Tmutants used by BEADLE, EPHRUSSI, TATUM and their collaborators in their early attempts to interpret the biochemical effects of genes (Cf. Review by EPHRUSI 1942). More recent studies on vermilion mutants (GREEN 1949, 1952, 1954) made it seem worthwhile to pursue further the study of the physiological effects of these mutants. The sex-linked, recessive vermilion ( U ) eye color mutants of D. melanogaster are characterized phenotypically by a lack of brown eye pigment under the usual genetic and environmental conditions. GREEN ( 1952) distinguished two series of vermilion mutants by their differential interaction with a nonallelic X chromosome mutant, suppressor of vermilion (su-U) . One group of u mutants approaches wild type in the production of brown eye pigment when combined with SU-U. This series may be designated us, indicating that it is suppressible by su-U. The other series may be designated vu, since it is unsuppressed by su-U. GREEN (1954) reported crossing over between a us allele ( U ’ ) and a vu allele ( ~ ~ ~ f ) indicating that they are pseudoallelic to each other. BARISH and Fox (1956) report that the vu mutant, uAsa, is allelic to v’ and pseudoallelic to STURTEVANT (1920) demonstrated by the use of gynandromorphs that the ~ ( u ’ = u s ) mutant was nonautonomous in development; i.e., flies which have genetically u eye tissue, but also contain U + tissue, may have phenotypically U + eyes. Transplantation of optic discs from u larvae into wild type larvae (EPHRUSSI and BEADLE 1935) confirmed the nonautonomous development of u with respect to wild type tissue. GREEN (1952) established developmental nonautonomy of the vu mutants ( ~ ~ ~ f , usla, u5lc) with respect to wild type tissue in gynandromorphs. Studies by TATUM (1939), TATUM and HAAGEN-SMIT (1941 ) , BUTENANDT, WEIDEL and BECKER (1940) and KIKKAWA (1941 ) establishcl i h genetically u flies will produce brown eye pigment if supplied with the tryptuphan metabolite, kynurenine, either by injection or in the larval food. GREEN (1949) found that large quantities of nonprotein tryptophan are dccumulated by flies carrying U’. Either kynurenine or its precursor, formylkynurenine, was shown to act as a precursor for brown eye pigment for both U’ ( u s )