REGULATION OF ACID-PHOSPHATASES IN AN ASPERGILLUS-NIGER PACC DISRUPTION STRAIN

Ail Aspergillus niger strain has been constructed in which the pH-depe ndent regulatory gene, pacC, was disrupted. The pacC gene of A. niger, like that of A. nidulans, is involved in the regulation of acid phosp hatase expression. Disruptants were identified by a reduction in acid phosphatase staining of colonies. Southern analysis demonstrated integ ration of the disruption plasmid al the pacC locus and Northern analys is showed that the disruption strain produced a truncated pacC mRNA of 2.2 kb (as compared to 2.8 kb ill the wild type). The strain carrying the pacC disruption was used; to assign the pacC gene to linkage grou p IV; this was confirmed by CHEF electrophoresis and Southern analysis . This strain further allowed us to determine which extracellular enzy me and transport systems are under the control of pacC in ii. niger. E xpression of the A. niger pacC wild-type gene and the truncated pacC g ene showed that,in contrast tct the auto-regulated wild-type expressio n,which was elevated only at alkaline pH, the truncated pacC gene was deregulated, as high-level expression occurred regardless of the pH of the culture medium. Analysis of the phosphatase spectrum by isoelectr ic focussing and enzyme activity staining both:in the wild-type and th e pacC disruptant showed that al least three acid phosphatases are reg ulated by the pacC. For the single alkaline phosphatase no pH regulati on was observed.