Ambient pH signaling influences phosphate acquisition in Neurospora crassa.

Patrick W. Kennedy , Robert L. Metzenberg , Maria J. Harrison and Wayne K. Versaw .

Author address: 

Dept of Biology, Texas A&M University, College Station, TX Dept of Chemistry and Biochemistry, University of California, Los Angeles, CA Boyce Thompson Institute for Plant Research, Cornell University, Ithica


N. crassa exhibits two modes of phosphate uptake constitutive, low-affinity transport and phosphate-repressible, high-affinity transport. The two transport systems can be operationally distinguished not only by available phosphate concentration but also by ambient pH. At pH values above neutrality, the Km of the low-affinity system rises sharply so that this system is unable to support growth under modest phosphate concentrations without the assistance of at least one component of the high-affinity system. Thus a mutant lacking the high-affinity transporters PHO-4 and PHO-5 is unable to grow under the restrictive conditions. The identity of the transporter(s) that comprise the low-affinity system has not been reported but a mutant isolated as a suppressor of the pho-4; pho-5 double mutant's growth defect displays altered phosphate transport activity. Complementation of this mutant revealed that the affected gene encodes a protein homologous to PalF of Aspergillus nidulans, which is one component of a highly conserved, ambient pH signaling pathway. Deletion of the pacC homolog, another component of the same pathway, gives rise to an identical phenotype indicating that pH signaling has a role in modulating low-affinity phosphate transport

abstract No: 


Full conference title: 

23rd Fungal Genetics Conference
    • Fungal Genetics Conference 23rd (2002)