RESUMEN
Aspergillus fumigatus is an aggressive opportunistic pathogen of humans as well as a major allergen. Environmental sensing and retrieving essential nutrients from the environment are general metabolic traits associated with the growth of this saprophytic fungus. Two important mediators of calcium signals in eukaryotic cells are the Ca(2+)-binding protein calmodulin and the Ca(2+)/calmodulin-dependent phosphatase calcineurin. Calcineurin is a heterodimer that consists of a catalytic subunit A and a Ca(2+)/calmodulin binding unit. We deleted the A. fumigatus calA gene, which encodes the calcineurin A catalytic subunit, and demonstrated that this gene is not essential in this fungus. The DeltacalA mutant strain has severe defects in growth extension, branching and conidial architecture. Furthermore, the A. fumigatus DeltacalA mutant strain has decreased fitness in a low dose murine infection and cannot grow in fetal bovine serum (FBS). After potassium phosphate was added to liquid FBS, the DeltacalA mutant strain could grow with the characteristic phenotype of the DeltacalA mutation. When A. fumigatus calcineurin is inhibited by tacrolimus in a phosphate depleted medium, there is a reduction in the inorganic phosphate transport and six putative phosphate transporter genes have altered mRNA levels. However, there is no effect on the acid phosphatase activity. These results suggest that calcineurin is involved in the regulation of the PHO pathway in A. fumigatus. Our work on calcineurin opens new venues for the research on sensing and nutrient acquisition in A. fumigatus.
Asunto(s)
Aspergillus fumigatus/enzimología , Calcineurina/metabolismo , Proteínas Fúngicas/metabolismo , Fosfatasa Ácida/metabolismo , Animales , Aspergillus fumigatus/genética , Aspergillus fumigatus/crecimiento & desarrollo , Calcineurina/genética , Dominio Catalítico/genética , Bovinos , Medios de Cultivo/química , Medios de Cultivo/farmacología , Sangre Fetal/química , Proteínas Fúngicas/genética , Proteínas Fúngicas/fisiología , Regulación Fúngica de la Expresión Génica/efectos de los fármacos , Hifa/efectos de los fármacos , Hifa/genética , Hifa/crecimiento & desarrollo , Proteínas de Transporte de Membrana/genética , Ratones , Ratones Endogámicos BALB C , Microscopía Electrónica de Rastreo , Mutación , Fosfatos/metabolismo , Fosfatos/farmacología , ARN Mensajero/genética , ARN Mensajero/metabolismo , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Esporas Fúngicas/genética , Esporas Fúngicas/ultraestructura , Tacrolimus/farmacología , Factores de TiempoRESUMEN
To increase the frequency of homologous recombination, we inactivated the KU80 homologue in Aspergillus fumigatus (named akuB(KU80)). Homologous integration reached about 80% for both calcineurin A (calA) and polyketide synthase pksP (alb1) genes in the akuB(KU80) mutant to 3 and 5%, respectively, when using a wild-type A. fumigatus strain. Deletion of akuB(KU80) had no influence on pathogenicity in a low-dose murine infection model.