Cloning of the regulatory gene areA mediating nitrogen metabolite repression in Aspergillus nidulans.

Abstract

The areA gene, which mediates nitrogen metabolite repression in the fungus Aspergillus nidulans, lies sufficiently close to a telomere that no indispensable gene can be distal to it. We were able therefore to exploit the existence of a near terminal pericentric inversion to devise a method for cloning areA plus the region beyond it towards the telomere. In crosses heterozygous for this inversion a class of duplication‐deficient progeny lacking areA and the region centromere‐distal to it is obtained. We, therefore, sought clones from an A. nidulans gene library in lambda Charon 4 able to hybridize to total genomic DNA from a wild‐type strain but not to that from a duplication‐deficiency strain. A clone, containing an 11.6‐kb insert, which hybridised weakly to duplication‐deficiency DNA, overlapped chromosome breakpoints of three different aberration‐associated areA alleles and was able to transform an areA mutant to areA+. Southern blotting and genetic analysis established that the transforming sequence had integrated in the region centromere distal to areA. The cloning method yielded other clones from the region centromere‐distal to areA which were used to show that the translocation associated with a mutant areA allele is reciprocal rather than non‐reciprocal, a fact which could not be established by classical genetics. Finally, analysis of the cloned portion of the dispensable region centromere‐distal to areA indicates that this region contains at least 0.5% of the A. nidulans genome.

Isolation of telomere DNA from Neurospora crassa.

“…The nature of the 30 kb of DNA between his-6 and the terminus is entirely unknown, but there is clearly DNA sequence variation among different N. crassa strains in this region. In the fungus Aspergillus nidulans, the distance between the telomere on the right arm of linkage group III and the nearest essential gene, areA, has been estimated to be much longer than between his-6 and its telomere, at least 130 kb (5). Any structural role for either of these large terminal regions cannot yet be established.…”

A Nitrogen Response Pathway Regulates Virulence Functions in Fusarium oxysporum via the Protein Kinase TOR and the bZIP Protein MeaB

“…Transcriptional regulation of nitrogen catabolic genes is mediated, in part, by the wide-domain regulators AreA in Aspergillus nidulans (Arst and Cove, 1973), Nit-2 in Neurospora crassa (Fu and Marzluf, 1987), and Gln3/Gat1 in Saccharomyces cerevisiae (Beck and Hall, 1999). These global nitrogen regulators are members of the GATA binding family of transcription factors and function as transcriptional activators of genes encoding pathway-specific permeases and enzymes enabling uptake and catabolism of secondary nitrogen sources (Caddick et al, 1986;Fu and Marzluf, 1990). As a consequence, loss-of-function mutants in AreA or Nit-2 are unable to use nitrogen sources other than Gln or ammonium (Arst and Cove, 1973;Marzluf, 1997).…”

Cloning and analysis of the positively acting regulatory gene amdR from Aspergillus nidulans.

“…This approach has allowed the cloning of a number of regulatory genes by various molecular techniques, e.g. the Neurospora crassa qa-JF (31) and qa-lS (10) genes and the Aspergillus nidulans prnA (6), alcR (23a), and areA (4) genes. The development of DNA-mediated transformation in lower eucaryotes has greatly facilitated the cloning of genetically defined regulatory genes by complementation; the N. crassa nit-2 (8,32) and cys-3 (28) regulatory genes have been cloned by this technique.…”