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The Aspergillus nidulans FcyB cytosine‐purine scavenger is highly expressed during germination and in reproductive compartments and is downregulated by endocytosis
Author(s) -
Vlanti Anna,
Diallinas George
Publication year - 2008
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.2008.06198.x
Subject(s) - biology , aspergillus nidulans , cytosine , purine metabolism , purine , biochemistry , yeast , gene , vacuolar protein sorting , gene expression , microbiology and biotechnology , saccharomyces cerevisiae , enzyme , mutant
Summary We cloned and characterized an Aspergillus nidulans gene, called fcyB , encoding the closest homologue to the yeast Fcy2p/Fcy21p permeases. Deletion of fcyB (Δ fcyB ) does not affect growth, development, reproduction or bulk purine uptake, but eliminates the leaky growth on purines of Δ azgA Δ uapC Δ uapA strains, lacking all known purine transporters, and confers resistance to the antifungal 5‐fluorocytosine. Kinetic analyses showed FcyB is a low‐capacity, high‐affinity, cytosine‐purine transporter sharing similar molecular interactions for substrate recognition with the yeast Fcy2p/Fcy21p carriers. fcyB transcription is highly activated during germination but drops at low constitutive levels throughout vegetative development. UaY‐mediated purine induction of fcyB transcription is only moderate, while ammonium represses transcription through an AreA‐dependent mechanism. A strain expressing FcyB–GFP confirms a low protein expression level in the plasma membrane of vegetative mycelia, but reveals an abundant expression in sexual and asexual compartments. FcyB–GFP was also shown to be downregulated by endocytosis in response to ammonia or the presence of cytosine. The expression profile of FcyB supports that its main physiological role is cytosine‐purine scavenging.