Varied expression of a Y-linked P[w(+)] insert due to imprinting in Drosophila melanogaster

During gametogenesis, a gene can become imprinted affecting its expression in progeny. We have used the expression of a Y-linked P[w(+)]YAL transposab le DNA element as a reporter system to investigate the effect of parental o rigination on the expression of the w(+) insert. Expression of w(+) was gre ater in male progeny when the Y chromosome, harboring the insert, was inher ited from the parental male rather than from the parental female. Imprintin g was not due to a genetic background influence in the males, since the onl y difference among the males was the parental origin of the Y chromosome. I t was also observed that the genetic background can affect imprinting, sinc e w(+) expression was also higher in males when the Y was derived from C(1) DX attached-X parental females rather than from C(1)RM attached-X parental females. Though the heterochromatic imprinting mechanism is unknown, a muta ted Heterochromatin Protein 1 (HP1) gene, which is associated with suppress ion of position-effect variegation, increases expression of the w(+) locus in the P[w(+)]YAL insert, indicating that HP1 may play a role in Y chromoso me packaging.