Functional characterization of the Aspergillus fumigatus PHO80 homologue

• Published in: Fungal genetics and biology 2008-07, Vol.45 (7), p.1135-1146
• Main Authors: de Gouvêa, Paula Fagundes, Soriani, Frederico Marianetti, Malavazi, Iran, Savoldi, Marcela, Goldman, Maria Helena de Souza, Loss, Omar, Bignell, Elaine, da Silva Ferreira, Márcia Eliana, Goldman, Gustavo Henrique
• Format: Article
• Language: English
• Subjects: Aspergillus fumigatus; Inorganic phosphate acquisition; PHO80; Protein kinase A
• ISSN: 1087-1845; 1096-0937
• DOI: 10.1016/j.fgb.2008.04.001

Phosphate is an ion that is essential for fungal growth. The systems for inorganic phosphate (P i) acquisition in eukaryotic cells ( PHO) have been characterized as a low-affinity (that assures a supply of P i at normal or high external P i concentrations) and a high-affinity (activated in response to P i starvation). Here, as an initial step to understand the PHO pathway in Aspergillus fumigatus, we characterized the PHO80 homologue, PhoB PHO80. We show that the ΔphoB PHO80 mutant has a polar growth defect (i.e., a delayed germ tube emergence) and, by phenotypic and phosphate uptake analyses, establish a link between PhoB PHO80, calcineurin and calcium metabolism. Microarray hybridizations carried out with RNA obtained from wild-type and ΔphoB PHO80 mutant cells identify Afu4g03610 ( phoD PHO84), Afu7g06350 ( phoE PHO89), Afu4g06020 ( phoC PHO81), and Afu2g09040 (vacuolar transporter Vtc4) as more expressed both in the ΔphoB PHO80 mutant background and under phosphate-limiting conditions of 0.1 mM P i. Epifluorescence microscopy revealed accumulation of poly-phosphate in ΔphoB PHO80 vacuoles, which was independent of extracellular phosphate concentration. Surprisingly, a phoD PHO84 deletion mutant is indistinguishable phenotypically from the corresponding wild-type strain. mRNA analyses suggest that protein kinase A absence supports the expression of PHO genes in A. fumigatus. Furthermore, ΔphoB PHO80 and ΔphoD PHO84 mutant are fully virulent in a murine low dose model for invasive aspergillosis.