Regulation of gliotoxin biosynthesis and protection in Aspergillus species

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de Castro, Patricia Alves ; Colabardini, Ana Cristina ; Moraes, Maisa ; Horta, Maria Augusta Crivelente ; Knowles, Sonja L. ; Raja, Huzefa A. ; Oberlies, Nicholas H. ; Koyama, Yasuji ; Ogawa, Masahiro ; Gomi, Katsuya ; Steenwyk, Jacob L. ; Rokas, Antonis ; Goncales, Relber A. ; Duarte-Oliveira, Claudio ; Carvalho, Agostinho ; Ries, Laure N. A. ; Goldman, Gustavo H.

• Document type: Journal article
• Source: PLOS GENETICS; v. 18, n. 1, p. 34-pg., 2022-01-01.

Abstract

Aspergillus fumigatus causes a range of human and animal diseases collectively known as aspergillosis. A. fumigatus possesses and expresses a range of genetic determinants of virulence, which facilitate colonisation and disease progression, including the secretion of mycotoxins. Gliotoxin (GT) is the best studied A. fumigatus mycotoxin with a wide range of known toxic effects that impair human immune cell function. GT is also highly toxic to A. fumigatus and this fungus has evolved self-protection mechanisms that include (i) the GT efflux pump GliA, (ii) the GT neutralising enzyme GliT, and (iii) the negative regulation of GT biosynthesis by the bis-thiomethyltransferase GtmA. The transcription factor (TF) RglT is the main regulator of GliT and this GT protection mechanism also occurs in the non-GT producing fungus A. nidulans. However, the A. nidulans genome does not encode GtmA and GliA. This work aimed at analysing the transcriptional response to exogenous GT in A. fumigatus and A. nidulans, two distantly related Aspergillus species, and to identify additional components required for GT protection. RNA-sequencing shows a highly different transcriptional response to exogenous GT with the RglT-dependent regulon also significantly differing between A. fumigatus and A. nidulans. However, we were able to observe homologs whose expression pattern was similar in both species (43 RglT-independent and 11 RglT-dependent). Based on this approach, we identified a novel RglT-dependent methyltranferase, MtrA, involved in GT protection. Taking into consideration the occurrence of RglT-independent modulated genes, we screened an A. fumigatus deletion library of 484 transcription factors (TFs) for sensitivity to GT and identified 15 TFs important for GT self-protection. Of these, the TF KojR, which is essential for kojic acid biosynthesis in Aspergillus oryzae, was also essential for virulence and GT biosynthesis in A. fumigatus, and for GT protection in A. fumigatus, A. nidulans, and A. oryzae. KojR regulates rglT, gliT, gliJ expression and sulfur metabolism in Aspergillus species. Together, this study identified conserved components required for GT protection in Aspergillus species. Author summary A. fumigatus secretes mycotoxins that are essential for its virulence and pathogenicity. Gliotoxin (GT) is a sulfur-containing mycotoxin, which is known to impair several aspects of the human immune response. GT is also toxic to different fungal species, which have evolved several GT protection strategies. To further decipher these responses, we used transcriptional profiling aiming to compare the response to GT in the GT producer A. fumigatus and the GT non-producer A. nidulans. This analysis allowed us to identify additional genes with a potential role in GT protection. We also identified 15 transcription factors (TFs) encoded in the A. fumigatus genome that are important for conferring resistance to exogenous gliotoxin. One of these TFs, KojR, which is essential for A. oryzae kojic acid production, is also important for virulence in A. fumigatus and GT protection in A. fumigatus, A. nidulans and A. oryzae. KojR regulates the expression of genes important for gliotoxin biosynthesis and protection, and sulfur metabolism. Together, this work identified conserved components required for gliotoxin protection in Aspergillus species. (AU)

• FAPESP's process: 18/10962-8 - The influence of G-protein-coupled receptors (GPCRs) on growth, morphogenesis and virulence of human pathogenic fungi
• Grantee: Gustavo Henrique Goldman
• Support Opportunities: Regular Research Grants
• FAPESP's process: 16/07870-9 - The influence of mitogen activated protein kinases (MAPK) on the expression of genetic determinants important for Aspergillus fumigatus virulence
• Grantee: Gustavo Henrique Goldman
• Support Opportunities: Research Projects - Thematic Grants
• FAPESP's process: 17/14159-2 - The role of lactose and acetate metabolism in Aspergillus fumigatus virulence
• Grantee: Laure Nicolas Annick Ries
• Support Opportunities: Research Grants - Young Investigators Grants
• FAPESP's process: 16/12948-7 - The role of mitogen-activated protein kinase (MPKA) MpkA in regulating gliotoxin production in Aspergillus fumigatus.
• Grantee: Patrícia Alves de Castro Silva
• Support Opportunities: Scholarships in Brazil - Post-Doctoral