Components of a new gene family of ferroxidases involved in virulence are functionally specialized in fungal dimorphism

Abstract

Mucormycosis is an emerging angio-invasive infection caused by Mucorales that presents unacceptable mortality rates. Iron uptake has been related to mucormycosis, since serum iron availability predisposes the host to suffer this infection. In addition, iron uptake has been described as a limiting factor that determines virulence in other fungal infections, becoming a promising field to study virulence in Mucorales. Here, we identified a gene family of three ferroxidases in Mucor circinelloides, fet3a, fet3b and fet3c, which are overexpressed during infection in a mouse model for mucormycosis, and their expression in vitro is regulated by the availability of iron in the culture media and the dimorphic state. Thus, only fet3a is specifically expressed during yeast growth under anaerobic conditions, whereas fet3b and fet3c are specifically expressed in mycelium during aerobic growth. A deep genetic analysis revealed partially redundant roles of the three genes, showing a predominant role of fet3c, which is required for virulence during in vivo infections, and shared functional roles with fet3b and fet3c during vegetative growth in media with low iron concentration. These results represent the first described functional specialization of an iron uptake system during fungal dimorphism.

Early Diverging Fungus Mucor circinelloides Lacks Centromeric Histone CENP-A and Displays a Mosaic of Point and Regional Centromeres

“…After at least five vegetative cycles, the integration in the target locus was confirmed by PCR using primers that amplified the whole locus (Table S2), producing PCR-fragments that allowed discrimination between the mutant and the wild-type locus ( Figure S3). Genomic DNA purification was performed following the procedure previously published [76]. Histone H3-ChIP assays were performed in the same way with the following changes.…”

A non-canonical RNAi pathway controls virulence and genome stability in Mucorales

“…The murine infection assays for Mucorales virulence were performed using OF-1 male mice weighing 30g (Charles River, Barcelona, Spain) [13,23,33]. The mice were immunosuppressed with the administration of cyclophosphamide (200 mg/kg of body weight) via intraperitoneal, 2 days prior to infection and once every 5 days thereafter.…”

Genes, Pathways, and Mechanisms Involved in the Virulence of Mucorales

“…Fungal pathogens possess sophisticated mechanisms to compete and steal iron from the host. In this sense, Mucorales show two different strategies for iron acquisition: a high-affinity iron uptake system and the production of siderophores [16,17].…”

“…In this triad, the permease and the ferroxidase are the key proteins for the correct functioning of the system. Iron levels in the medium strictly regulate these three genes [17]. Thus, low availability of iron triggers the expression of the high-affinity iron uptake mechanism in Rhizopus delemar [18], M. circinelloides [17], and Lichtheimia corymbifera [19].…”

“…Iron levels in the medium strictly regulate these three genes [17]. Thus, low availability of iron triggers the expression of the high-affinity iron uptake mechanism in Rhizopus delemar [18], M. circinelloides [17], and Lichtheimia corymbifera [19]. In fact, the expression of the ferroxidase genes is controlled by low iron concentration when the medium is treated both with synthetic iron chelators (like 1,10-phenanthroline) and with fetal bovine serum.…”