title: Transcription of purine transporter genes is activated during the isotropic growth phase of Aspergillus nidulans conidia.
abstract: Aspergillus nidulans possesses three well-characterized purine transporters encoded by the genes uapA, uapC and azgA. Expression of these genes in mycelium is induced by purines and repressed by ammonium or glutamine through the action of the pathway-specific UaY regulator and the general GATA factor AreA respectively. Here, we describe the regulation of expression of purine transporters during conidiospore germination and the onset of mycelium development. In resting conidiospores, mRNA steady-state levels of purine transporter genes and purine uptake activities are undetectable or very low. Both mRNA steady-state levels and purine transport activities increase substantially during the isotropic growth phase of conidial germination. Both processes occur in the absence of purine induction and independently of the nitrogen source present in the medium. The transcriptional activator UaY is dispensable for the germination-induced expression of the three transporter genes. AreA, on the other hand, is essential for the expression of uapA, but not for that of azgA or uapC, during germination. Transcriptional activation of uapA, uapC and azgA during germination is also independent of the presence of a carbon source in the medium. This work establishes the presence of a novel system triggering purine transporter transcription during germination. Similar results have been found in studies on the expression of other transporters in A. nidulans, suggesting that global expression of transporters might operate as a general system for sensing solute availability.
authors.affiliation: Faculty of Biology, Department of Botany, University of Athens, Panepistimioupolis, Athens 15781, Greece.
authors.forename: Sotiris
authors.initials: S
authors.lastname: Amillis
authors.forename: Gianna
authors.initials: G
authors.lastname: Cecchetto
authors.forename: Vicky
authors.initials: V
authors.lastname: Sophianopoulou
authors.forename: Marina
authors.initials: M
authors.lastname: Koukaki
authors.forename: Claudio
authors.initials: C
authors.lastname: Scazzocchio
authors.forename: George
authors.initials: G
authors.lastname: Diallinas
mesh_terms: D001233:Aspergillus nidulans / Q000235:genetics* / Q000254:growth & development / Q000502:physiology*; D015152:Blotting, Northern; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D015966:Gene Expression Regulation, Fungal; D005800:Genes, Fungal; D019271:Hypoxanthine / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism; D025282:Mycelium / Q000254:growth & development; D033702:Nucleobase Transport Proteins / Q000235:genetics* / Q000378:metabolism; D011687:Purines / Q000378:metabolism*; D013172:Spores, Fungal / Q000235:genetics / Q000378:metabolism; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D019820:Xanthine / Q000378:metabolism
chemical_list: C079728:AreA protein, Aspergillus nidulans; D005656:Fungal Proteins; D026901:Membrane Transport Proteins; D033702:Nucleobase Transport Proteins; D011687:Purines; D015534:Trans-Activators; D014157:Transcription Factors; C083852:UAPA protein, Aspergillus nidulans; C093266:UaY protein, Aspergillus nidulans; C114088:UapC protein, Aspergillus nidulans; D019820:Xanthine; D019271:Hypoxanthine