Biology subjects

Fill, T. P.

Publications and source records attributed to Fill, T. P..

4 recordsLinked to original sources

bioRxiv2021

Aspergillus fumigatus acetate utilisation impacts virulence traits and pathogenicity

Aspergillus fumigatus is a major opportunistic fungal pathogen of immunocompromised and immunocompetent hosts. To successfully establish an infection, A. fumigatus needs to use host carbon sources, such as acetate, present in the body fluids and peripheral tissues. However, utilisation of acetate as a carbon source by fungi in the context of infection has not been investigated. This work shows that acetate is metabolised via different pathways in A. fumigatus and that acetate utilisation is under the regulatory control of a transcription factor (TF), FacB. A. fumigatus acetate utilisation is subject to carbon catabolite repression (CCR), although this is only partially dependent on the TF and main regulator of CCR CreA. The available extracellular carbon source, in this case glucose and acetate, significantly affected A. fumigatus virulence traits such as secondary metabolite secretion and cell wall composition, with the latter having consequences for resistance to oxidative stress, to anti-fungal drugs and to human neutrophil-mediated killing. Furthermore, deletion of facB significantly impaired the in vivo virulence of A. fumigatus in both insect and mammalian models of invasive aspergillosis. This is the first report on acetate utilisation in A. fumigatus and this work further highlights the importance of available host-specific carbon sources in shaping fungal virulence traits and subsequent disease outcome, and a potential target for the development of anti-fungal strategies. ImportanceAspergillus fumigatus is an opportunistic fungal pathogen in humans. During infection, A. fumigatus is predicted to use host carbon sources, such as acetate, present in body fluids and peripheral tissues, to sustain growth and promote colonisation and invasion. This work shows that A. fumigatus metabolises acetate via different pathways, a process that is dependent on the transcription factor FacB. Furthermore, the type and concentration of the extracellular available carbon source were determined to shape A. fumigatus virulence determinants such as secondary metabolite secretion and cell wall composition. Subsequently, interactions with immune cells are altered in a carbon source-specific manner. FacB is required for A. fumigatus in vivo virulence in both insect and mammalian models of invasive aspergillosis. This is the first report that characterises acetate utilisation in A. fumigatus and highlights the importance of available host-specific carbon sources in shaping virulence traits and potentially subsequent disease outcome.

microbiology↗

bioRxiv2021

Chromatin profiling reveals genome stability heterogeneity in clinical isolates of the human pathogen Aspergillus fumigatus

Invasive Pulmonary aspergillosis is a life-threatening infection in immunosuppressed patients caused by the filamentous fungus Aspergillus fumigatus. Chromatin structure regulation is important for genome stability maintenance and has the potential to lead to genome rearrangements driving differences in virulence and pathogenesis of different A. fumigatus isolates. Here, we compared the chromatin activities of the most investigated clinical isolates Af293 and CEA17 and uncovered striking differences in the number, locations and expression of transposable elements. We found evidence for higher genome instability in Af293 as compared to CEA17 and identified a spontaneous Af293 variant that exhibits gross chromosomal alterations including the loss of a 320 kb long segment in chromosome VIII and the amplification of a biosynthetic gene cluster. As a consequence of these re-arrangements, the variant shows increased secondary metabolites production, growth and virulence. Our work emphasizes genome stability heterogeneity as an evolutionary driver of A. fumigatus fitness and virulence.

molecular biology↗

bioRxiv2020

Phytotoxic tryptoquialanines produced in vivo by Penicillium digitatum are exported in extracellular vesicles

Penicillium digitatum is the most aggressive pathogen of citrus fruits. Tryptoquialanines are major indole alkaloids produced by P. digitatum. It is unknown if tryptoquialanines are involved in the damage of citrus fruits caused by P. digitatum. To investigate the pathogenic roles of tryptoquialanines, we initially asked if tryptoquialanines could affect the germination of Citrus sinensis seeds. Exposure of the citrus seeds to tryptoquialanine A resulted in a complete inhibition of germination and an altered metabolic response. Since this phytotoxic effect requires the extracellular export of tryptoquialanine A, we investigated the mechanisms of extracellular delivery of this alkaloid in P. digitatum. We detected extracellular vesicles (EVs) released by P. digitatum both in culture and during infection of citrus fruits. Compositional analysis of EVs produced during infection revealed the presence of a complex cargo, which included tryptoquialanines and the mycotoxin fungisporin. The EVs also presented phytotoxicity activity in vitro, and caused damage to the tissues of citrus seeds. Through molecular networking, it was observed that the metabolites present in the P. digitatum EVs are produced in all of its possible hosts. Our results reveal a novel phytopathogenic role of P. digitatum EVs and tryptoquialanine A, implying that this alkaloid is exported in EVs during plant infection. IMPORTANCEDuring the post-harvest period, citrus fruits can be affected by phytopathogens such as Penicillium digitatum, which causes the green mold disease and is responsible for up to 90 % of the total citrus losses. Chemical fungicides are widely used to prevent the green mold disease, leading to concerns about environmental and health risks. To develop safer alternatives to control phytopathogens, it is necessary to understand the molecular basis of infection during the host-pathogen interaction. In the P. digitatum model, the virulence strategies are poorly known. Here, we describe the production of phytotoxic extracellular vesicles (EVs) by P. digitatum during the infection of citrus fruits. We also characterized the secondary metabolites in the cargo of EVs and found in this set of molecules an inhibitor of seed germination. Since EVs and secondary metabolites have been related to virulence mechanisms in other host-pathogen interactions, our data are important for the comprehension of how P. digitatum causes damage to its primary hosts.

microbiology↗

bioRxiv2020

The histone deacetylase clr3regulates secondary metabolite production and growth under oxidative stress conditions in Penicillium brasilianum

Most of the biosynthetic gene clusters (BGCs) found in filamentous fungi are silent under standard laboratory cultivation conditions due to the lack of expression triggering stimuli, representing a considerable drawback in drug discovery. To access the full biosynthetic potential of these microbes, studies towards the activation of cryptic BGCs are essential. Histone acetylation status is an important regulator of chromatin structure which impacts in cell physiology and, therefore, expression of biosynthetic gene clusters in filamentous fungi. Histone deacetylases (HDACs) and histone acetyl-transferases (HATs) are responsible for maintaining and controlling this process under different cell conditions. In this study, clr3, a gene encoding a histone deacetylase in Penicillium brasilianum was deleted and associated phenotypic and metabolic changes evaluated. Results indicate reduced growth under oxidative stress conditions in the {Delta}clr3 knockout strain. Also, the production of several secondary metabolites including austin-related meroterpenoids, brasiliamides, mycotoxins such as verruculogen and penicillic acid, as well as cyclodepsipeptides was reduced in the {Delta}clr3 strain when compared to wild-type strain. Accordingly, addition of epigenetic modulators responsible for HDAC inhibition such as suberoylanilide hydroxamic acid (SAHA) and nicotinamide (NAA) to P. brasilianum growth media also culminated in reduction of secondary metabolite production. Mass Spectrometry Imaging (MSI) was applied to compare metabolite production and spatial distribution on the colony. Results suggest that Clr3 plays an important role in secondary metabolite biosynthesis in P. brasilianum, thus offering new strategies for regulation of natural product synthesis by assessing chromatin modification in P. brasilianum.

microbiology↗