Biology subjects

Guruceaga, X.

Publications and source records attributed to Guruceaga, X..

3 recordsLinked to original sources

bioRxiv2023

The Aspergillus fumigatus maiA gene contributes to cell wall homeostasis and fungal virulence.

In this study, two distinct in vitro infection models of Aspergillus fumigatus, using murine macrophages (RAW264.7) and human lung epithelial cells (A549), were employed to identify the genes important for fungal adaptation during infection. Transcriptomic analyses of co-incubated Aspergillus uncovered 140 fungal genes up-regulated in common between both models that, when compared with a previously published in vivo transcriptomic study, allowed the identification of 13 genes consistently up-regulated in all three infection conditions. Among them, the maiA gene, responsible for a critical step in the L-phenylalanine degradation pathway, was identified. Disruption of maiA resulted in a mutant strain unable to complete the Phe degradation pathway, leading to an excessive production of pyomelanin when this amino acid served as the sole carbon source. Moreover, the disruption mutant exhibited noticeable cell wall abnormalities, with reduced levels of {beta}-glucans within the cell wall. the maiA-1 mutant strain induced reduced inflammation in primary macrophages and displayed significantly lower virulence in a neutropenic mouse model of infection. This is the first study linking the A. fumigatus maiA gene to fungal cell wall homeostasis and virulence.

microbiology↗

bioRxiv2023

The sterol C-24 methyltransferase encoding gene, erg6, is essential for viability of Aspergillus species.

Ergosterol is a critical component of fungal plasma membranes. Although many currently available antifungal compounds target the ergosterol biosynthesis pathway for antifungal effect, current knowledge regarding ergosterol synthesis remains incomplete for filamentous fungal pathogens like Aspergillus fumigatus. Here, we show for the first time that the lipid droplet-associated sterol C-24 methyltransferase, Erg6, is essential for A. fumigatus viability. We further show that this essentiality extends to additional Aspergillus species, including A. lentulus, A. terreus, and A. nidulans. Neither the overexpression of a putative erg6 paralog, smt1, nor the exogenous addition of ergosterol could rescue erg6 deficiency. Importantly, Erg6 downregulation results in a dramatic decrease in ergosterol and accumulation in lanosterol and is further characterized by diminished sterol-rich plasma membrane domains (SRDs) at hyphal tips. Unexpectedly, erg6 repressed strains demonstrate wild-type susceptibility against the ergosterol-active triazole and polyene antifungals. Finally, repressing erg6 expression reduced fungal burden accumulation in a murine model of invasive aspergillosis. Taken together, our studies suggest that Erg6, which shows little homology to mammalian proteins, is potentially an attractive antifungal drug target for therapy of Aspergillus infections. IMPORTANCEA. fumigatus is the most common pathogen that causes invasive aspergillosis, a life-threatening fungal infection with more than 300,000 cases reported annually. Available antifungals to treat Aspergillus-related infection are limited to three drug classes targeting the plasma membrane (ergosterol) or the cell wall, each of which suffer from either host toxicity or rising resistance levels. As ergosta-type sterols are absent in mammalian cells but are essential for fungal viability, the ergosterol biosynthesis pathway remains an enticing target for the development of new antifungals. Although ergosterol biosynthesis has been well studied in model yeast, only a few genes have been genetically characterized in A. fumigatus. Here, we characterize Erg6, one of the fungus-specific sterol biosynthesis genes, as an essential gene in Aspergillus species. We further provide in vivo evidence of the importance of Erg6 for establishment of invasive aspergillosis. Given the importance of Erg6 in other fungal systems for growth, stress resistance, and virulence, our study suggests that development of Erg6 inhibitors may be a promising strategy for developing novel broad-spectrum antifungals.

microbiology↗

bioRxiv2023

Identification and functional characterization of the putative members of the CTDK-1 kinase complex as regulators of growth and development in the genus Aspergillus.

The genus Aspergillus includes industrially, medically and agriculturally important species. All of them, as do fungi in general, disperse to new niches principally by means of asexual spores. Regarding the genetic/molecular control of asexual development, Aspergillus nidulans is the main reference. In this species, two pathways control the production of conidiophores, the structures bearing asexual spores (conidia). The Upstream Developmental Activation (UDA) pathway transduces environmental signals, determining whether the Central Developmental Pathway (CDP) and the required morphological changes are induced. The transcriptional regulator BrlA links both pathways as loss-of-function mutations in flb (UDA) genes block brlA transcription and, consequently, conidiation. However, the aconidial phenotype of specific flb mutants is reverted under salt-stress conditions. Previously, we generated a collection of {Delta}flbB mutants unable to conidiate on culture medium supplemented with NaH2PO4 (0.65M). Here, we identified a Gly347Stop mutation within flpA as responsible for the FLIP57 phenotype. The putative cyclin FlpA and the remaining putative components of the C-terminal domain kinase-1 (CTDK-1) complex are necessary for proper germination, growth and developmental patterns in both A. nidulans and A. fumigatus. Cellular localization and functional interdependencies of the three proteins are also analyzed. Overall, this work links the putative CTDK-1 complex of aspergilli with growth and developmental control. One-sentence summaryIdentification of a mutation in flpA as inhibitor of conidiation in A. nidulans and functional characterization of FlpA, Stk47 and FlpB as putative members of the C-terminal domain kinase complex CTDK-1 in the genus Aspergillus.

microbiology↗