POSITION EFFECTS AND VARIEGATION ENHANCERS IN AN AUTOSOMAL REGION OF DROSOPHILA MELANOGASTER

Abstract

A dominant eye color mutation was found associated with a third chromosome inversion broken distally at or near the karmoisin (kar) locus in 87C and proximally within centric heterochromatin. Suppressibility of the mutant phenotype by an extra Y chromosome indicated that this was an example of dominant position-effect variegation. When heterozygous with deficiencies uncovering the kar locus, this inversion chromosome was found to be lethal unless a region in 87EF was also deleted. Extra Y chromosomes rescued inversion/deletion heterozygotes, while removal of the Y chromosome from heterozygous males deficient for the region in 87EF was lethal. Thus, a variegating lethal lies near the breakpoint in 87C, and a wild-type gene that enhances its variegation lies in 87EF. Furthermore, deletion of the region in 87EF was found to strongly suppress white-mottled-4 (wm4) variegation, while deletion of another region in 87BC suppressed less strongly. These results indicate that essential genes on autosomes are sensitive to position effects, and loci that enhance variegation, as defined by deficiency mapping, are very common.

Knockdowns of red Malphigian tubules reveal pigmentation roles in the milkweed bug

“…The Drosophila red M. tubules (red) eye color mutations were first described in the 1950s (Aslaksen & Hadorn, 1957;Oster, 1954), and have been used as a marker gene (Breen & Harte, 1991;Henikoff, 1979;Paton pigmented Malpighian tubules, with an overall decreased content of ommochromes and pterins, except for a strong accumulation of colorless biopterin in eyes, and of the ommochromes xanthommatin and ommin A in Malpighian tubules (Ferré et al, 1986;Ruiz-Vázquez et al, 1996;Silva et al, 1991;Wessing & Bonse, 1966). Red was recently mapped to a LysM-domain containing protein in Drosophila (Grant et al, 2016).…”

Genetics of continuous colour variation in a pair of sympatric sulphur butterflies

“…This gene encodes protein with a conserved LysM domain, although its molecular function has seldom been studied. The Drosophila mutant strain red Malpighian tubules ( red ) was described in 1954 (Oster, 1954) and has been used as a marker gene (Henikoff, 1979; Breen and Harte, 1991), but its molecular annotation to the red coding gene was only recently described (Grant et al, 2016).…”

“…The North American sulphur butterflies C. philodice and C. eurytheme, co-exist in sympatry while maintaining effective reproductive barriers (Wang and Porter, 2004), and the Z sex chromosome plays a disproportionate role in keeping these species distinct, an effect known as the Large-X effect (Presgraves, 2018). Moreover, the Z chromosome has a remarkably high level of divergence compared to autosomes (Ficarrotta et al, 2022), and it also acts as a large linkage group coupling key reproductive barrier traits such as asymmetric hybrid female sterility, both male pheromone signal and female preference, as well as male UV signal and female preference; it thereby acts as a cluster of loci involved in incipient speciation (Grula et al, 1980;Grula and Taylor, 1980b, 1980a, 1979. The UV colouration signal, a recessive marker that distinguishes C. eurytheme males from hybrids and allows conspecific females to find compatible gametes, is explained by allelic variation of the bab transcription factor, a suppressor of UV scales that is specifically de-repressed in a small fraction of cells in iridescent males.…”