Gene inactivation system extension into a unique sequence outside of the II →> I insertional duplication in Aspergillus nidulans
The first report of the gene inactivation system (GIS) in Aspergillus nidulans came from crosses involving a II Gene inactivation system extension into a unique sequence outside of the II →> I insertional duplication. Duplicated segments trigger the GIS that acts through the methylation of cytosines present within repeats. Duplicated genes are probably inactivated during the premeiotic period between fertilization and karyogamy, but reactivation may occur spontaneously or after 5-azacytidine treatment. The aim of the present study was to determine the action of GIS on a single copy gene located near a duplicated segment. Aspergillus nidulans strains bearing the Dp(II,I) duplication were used in meiotic crosses homozygous for the y+ gene and yellow (y) segregants were recovered among the progenies. Data show that the GIS can act on a closely linked gene outside the duplicated segment, promoting reversible inactivation. Reduction of ascospore numbers and viability were observed in crosses parented by duplication strains. Inactivation of the w+ gene in a w/w+ duplication strain is also shown.Key words: Aspergillus nidulans, gene inactivation, DNA methylation, chromosomal duplication.