Sex determination in the flour moth, Ephestia kuehniella.. Moth sex determination

In moths and butterflies (Lepidoptera) as well as their sister group caddis flies (Trichoptera) females are heterogametic while males are homogametic. Female Lepidoptera have mostly a WZ sex chromosome constitution but W1W2Z, WZ1Z2 or Z0 do occur. It is obvious that sex determination in species with Z0 females and ZZ males rests on some counting mechnism of one or more Z linked genes. This could also be true for species with WZ, WZ1Z2, or W1W2Z females. But it has long been known that in the silkworm, Bombyx mori, the W chromoome carries a female-determimng gene, F. Presence or absemce of F decides upon the sexual development of the embryo, irrespective of the number of Z chromosomes. It is not known yet whether all WZ species follow the B. mori scheme.of sex determination.Molecularly, F is a gene that produces a piRNA which inhibits the action of a Z-linked gene Masculinizer (Masc) and thereby turns on the pathway to female development of the embryo. Masc is thought to provide the signal for male development. In species with Z0 female and ZZ males, the dosage of Masc is supposed to decide upon the sexual development of the embryo.The primary sex-determining signal controls directly or via some unknown intermediate step female- or male-type splicing of doublesex (dsx). Dsx in turn regulates female or male developmemt. There are a couple of other genes whose activity is required for the correct expression of dsx.This is a study of the sex-determining pathway of Ephestia uehniells, the flour moth, a species with WZ females and ZZ males.