Genetic and environmental modification of gene expression in thebrlA12variegated position effect mutant ofAspergillus nidulans

Abstract

SUMMARYThebrlA12variegated position effect mutant is particularly suited for tests of environmental and genetic influences on variegation, but out of a large number of substances added to the medium, only salts at high concentrations and methylamine significantly increased expression of this gene. Medium shifting experiments showed thatbrlA12activity could be switched on late, but once active, was rarely switched off again during conidiation. SeparatebrlA12clones in heterokaryons were activated independently. SomebrlA12-specific suppressor mutants, including those at loci giving almost complete suppression, have been studied. One class of suppressors also confers inability to utilize galactose as carbon source and comparison with other, pre-existing mutants showed that thebrlA12phenotype was either suppressed or enhanced by mutants with complex phenotypes involving galactose utilization, molybdate resistance, acid phosphatase production and sulphur metabolism. Tests for the involvement of DNA methylation inbrlA12expression gave negative results.