CATA, A NEW ASPERGILLUS-NIDULANS GENE ENCODING A DEVELOPMENTALLY-REGULATED CATALASE

Aspergillus nidulans asexual sporulation (conidiation) is a model syst em for studying gene regulation and development. The CAN5 cDNA is one of several clones isolated based on transcript induction during conidi ation. Here we present the molecular characterization of its correspon ding gene, demonstrating that it encodes a developmentally regulated c atalase, designated catA. The catA 744-amino-acid-residue polypeptide shows significant identity to other catalases. Its similarity to proka ryotic catalases is greater than to other fungal catalases. catA mRNA is barely detectable in growing mycelia, highly induced during sporula tion, and present in isolated spores. However, catA expression is not dependent on the developmental regulatory genes brlA, abaA and wetA. D irect catalase activity determination in native gels revealed the exis tence of two bands of activity. One of these bands represented the maj or activity during vegetative growth and was induced during sporulatio n. The second catalase activity appeared after the induction of sporul ation and was the predominant activity in spores. Disruption of catA a bolished the major spore catalase without eliminating the vegetative a ctivity, indicating the existence of at least two catalase genes in A. nidulans. catA-disrupted mutants produced spores that were sensitive to H2O2, as compared to wild-type spores. The increase in the activity of the vegetative catalase and the appearance of a second catalase du ring asexual sporulation is consistent with the occurrence of an oxida tive stress during development.