Polarity-defective mutants of Aspergillus nidulans

Osherov, N., Mathew, J., and May, G. S. 2000, Polarity-defective mutants of Aspergillus nidulans, Fungal Genetics and Biology 31, 181-188, We have ide ntified two polarity-defective (pod) mutants in Aspergillus nidulans from a collection of heat-sensitive lethal mutants, At restrictive temperature, t hese mutants are capable of nuclear division but are unable to establish po lar hyphal growth, We cloned the two pod genes by complementation of their heat-sensitive lethal phenotypes, The libraries used to clone the pod genes are under the control of the bidirectional niaD and niiA promoters. Comple mentation of the pod mutants is dependent on growth on inducing medium. We show that rescue of the heat-sensitive phenotype on inducing media is indep endent of the orientation of the gene relative to the niaD or niiA promoter s, demonstrating that the intergenic region between the niaD and the niiA g enes functions as an orientation-independent enhancer and repressor that is capable of functioning over long distances. The products of the podG and t he podH genes were identified as homologues of the alpha subunit: of yeast mitochondrial phenylalanyl-tRNA synthetase and transcription factor IIF int eracting component of the CTD phosphatase, Neither of these gene products w ould have been predicted to produce a pod mutant phenotype based on studies of cellular polarity mutants in other organisms. The implications of these results are discussed. (C) 2000 Academic Press.