J.S. Freitas, E.M. Silva, A. Rossi
Published September 30, 2007
Genet. Mol. Res. 6 (3): 721-729 (2007)

About the authors
J.S. Freitas, E.M. Silva, A. Rossi

Corresponding author
A. Rossi
E-mail: anrossi@usp.br

ABSTRACT

 The present study was designed to identify nutrient-de- pendent changes in extracellular pH and acid phosphatase secretion in the biAl palC4 mutant strain of Aspergillus nidulans. The palC4 mutant was selected as lacking alkaline phosphatase, but having substantially in- creased acid phosphatase activity when grown on solid minimal medium under phosphate starvation, pH 6.5. Gene palC was identified as a puta- tive member of a conserved signaling cascade involved in ambient alka- line sensing whose sole function is to promote the proteolytic activation of PacC at alkaline pH. We showed that both poor growth and conidiation of the palC4 mutant strain on solid medium, alkaline pH, were relative to its hypersensitivity to Tris (hydroxymethyl) aminomethane buffer. Also, the secretion of acid phosphatase was repressed when both the wild-type and palC4 mutant strains were grown in low-phosphate yeast extract liq- uid medium, pH 5.0, indicating that the secretion of this enzyme is not necessary to regenerate inorganic phosphate from the organic phosphate pool present in yeast extract.

Key words: Acid phosphatase, Aspergillus nidulans, Colonial growth, Enzyme secretion, palC gene, Ambient pH