A functional genomics approach: Characterisation of two Non-ribosomal peptide synthetase genes, and investigation of an adaptive response towards alkylating DNA damage in Aspergillus fumigatus.
Year: 2010
Type: dissertation
Abstract: Aspergillus fumigatus is a serious opportunistic human pathogen. Availability of the\ncomplete genome sequence of A. fumigatus allows the identification and subsequent\ncharacterisation of genes which may encode virulence factors, or novel drug targets. Nonribosomal\npeptide (NRP) synthetases have been implicated in virulence of A. fumigatus and other\nfungi. The work presented here reports opposing roles for two previously uncharacterised NRP\nsynthetases with respect to A. fumigatus virulence. The NRP synthetase Pes3 appears to encode a\nstructural peptide necessary for fungal recognition by the innate immune system; deletion of pes3\nresulted in hypervirulence in both insect (p < 0.001) and murine (p = 0.02) models of invasive\naspergillosis, and increased susceptibility to voriconazole (p < 0.001). The NRP synthetase PesL\nwas found to be essential for fumigaclavine C biosynthesis and deletion of pesL resulted in\ncomplete loss of fumigaclavine C accompanied by severely reduced virulence (p < 0.001),\nincreased sensitivity of ΔpesL to H2O2 (> 1 mM) (p = 0.05), and increased sensitivity to the antifungal\nvoriconazole (> 0.25 μg/ml) (p < 0.01) compared to wild-type.\nAn adaptive response to alkylating agents (e.g. N-methyl-N′-nitro-N-nitrosoguanidine\n(MNNG)) was identified in A. fumigatus. Afmpt is a transcriptional regulator for this response,\nand exposure to MNNG causes up-regulation of Afmpt and Afagt, an alkylguaninetransferase.\nAfmpt and Afagt functions were confirmed through targeted gene deletion, phenotypic and\nexpression analyses, and yeast complementation studies. Identification of this response, which\nhas no mammalian equivalent, makes this pathway an attractive anti-fungal drug target worthy of\nfurther investigation.\nOverall, this work further highlights the importance that NRPS plays in this serious\nhuman pathogen, and uncovered some interesting features such as possible secondary metabolite\ncluster cross-talk and NRP synthetase redundancy, themes which are beginning to emerge in the\nliterature.
Author: Karen O’Hanlon
Language: English
Subfield: Applied Microbiology and Biotechnology
Field: Immunology and Microbiology
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W603717974