Gene Dmel\z

The regulatory gene zeste interacts with the white locus as well as with the bithorax and decapentaplegic complexes, changing the phenotypic expression of these loci. z1 was the first mutant allele identified (Gans, 1948, 1953); the homo- or hemizygotes of this neomorphic mutant show a lemon yellow eye color when carrying two paired copies of w+ or of the rightmost w+ alleles [as in z1 w+/z1 w+ females or z1/Y males with a w+ duplication (Jack and Judd, 1979)]. z1 w+/Y males without the duplication, z1/z1 females heterozygous for a w allele belonging to one of the right-hand (zeste-suppressing) subloci, or z+/z1 females are wild type. An intralocus duplication for a right sublocus of white produces mottling in z1 males. z1 eye color develops autonomously in mosaics and in eye-disk transplants. It is not affected by the number of Y chromosomes in the genotype. A third chromosome mutant wo interacts with z1 or z58g to lighten eye color, producing z/z;wo/wo white-eyed females and z/Y;wo/wo males with a slight deviation from wild-type eye color (Rayle, 1969, DIS 44: 98; Kaufman et al., 1973). z1 has no effect on the expression of the white gene in ocelli, testes, or larval Malphigian tubules. The first za mutant was also identified by Gans. These mutants are wild type in za/Y males and za/za, za/Df(1)z, and z+/za females. The heteroallelic combination of z1/za, however, results in yellow-eyed flies. Complementation between wsp and other white alleles does not occur in za mutants, although it does occur in z+ or z1 flies (Babu and Bhat, 1980). za-type alleles, including zae(bx), as well as the partial revertant of z1, z11G3, enhance the mutant phenotype of certain heteroallelic combinations of BXC alleles that show transvection (partial complementation) when paired; z+ and z1, however, do not affect these BXC alleles (Kaufman et al., 1973; Gelbart and Wu, 1982; Mariani et al., 1985; Pirrotta et al., 1987). All zeste mutant alleles tested enhance certain heteroallelic mutant combinations that show transvection in dpp (Gelbart and Wu, 1982). The zop mutants (Lifschytz and Green, 1984), unlike z1, require only one copy of w+ for expression of a zeste eye color in homo- and hemizygotes. Heterozygotes over z+ are zeste if they have two copies of w+, but are wild type if there is only one copy. Another mutant, zv77h, requires only one copy of w+ in males. The eyes are brown variegated in hemi- and homozygous zv77h females and zv77h/Y males, but wild type in homozygous zv77h Dp(1;1)w+2 females and zv77h Dp(1;1)w+2/Y males, this allele responding to an increase in w+ dosage in a manner contrary to that of z1 (Green, 1984). Diepoxy-butane-induced mutations (including multilocus deletions) have been generated in an attempt to obtain a null allele of zeste (Goldberg et al., 1989). Some of the females that were completely deficient for z [Df(1)z-deb3/Df(1)z-deb3, for example] survived and were fertile, indicating that the product of the zeste gene is not required for viability or female fertility.

Two synapsed copies of w+ required for expression of zeste eye color (Gans, 1953). Ocelli wild type in color, as are testes and larval Malpighian tubules. Supports transvection at Ubx but not at dpp.

Partial revertant of z1 showing wild-type eye color in hemizygous males and homozygous females (Gans, 1953). Almost complete complementation of z1 eye color. Does not support transvection at dpp or Ubx.

Hemizygous males and homozygous females said to be wild type in eye color (Gans); however, on closer inspection they are seen to have a diluted eye color that becomes brown with age (Pirrotta et al., 1987). z1/za females have zeste eyes; za wDZL/za wch females have light brown eyes. Does not support transvection at dpp or Ubx.

Mostly wild type, but slight eye color variegation in homozygous females (Lewis, 1959, DIS 33: 96). z1/zae(bx) females zeste. Does not support transvection at dpp or Ubx.

Eye color zeste in hemizygous males and homozygous females with only one copy of w+; homozygous females with two copies of w+ also zeste. Heterozygous z+/zop6 females wild type if one copy of w+, but zeste if two copies; zop6 reverts to weaker alleles after EMS or X rays (Lifschytz and Green, 1984).

Hemizygous males and homo- or hemizygous females almost wild type in eye color. Supports transvection at Ubx (Pirrotta et al., 1987).

Eye color diluted, turning brownish with age in hemizygous males and hemi- and homozygous females with a normal complement of w+ genes. za/zv77h females are wild type; z1/zv77h females are zeste; zv77h hemizygous males and homozygous females carrying a w+ duplication in each X are wild type.