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RNA-seq analysis of wt Metschnikowia pulcherrima cells and a spontaneous mutant (W8) in the snf2 gene that exhibited differential expression of the recently described pulcherrimin genes

ABSTRACT: We analyzed differential gene expression in wt and a snf2 mutant (W8) cells; the pucherimin biosynthesis genes were among the top diff. regulated genes (reduced expression in the mutant). ABSTRACT: Metschnikowia pulcherrima synthesizes the pigment pulcherrimin, from cyclodileucine (cyclo(Leu-Leu)) as a precursor, and exhibits strong antifungal activity against notorious plant pathogenic fungi. This yeast therefore has great potential for biocontrol applications against fungal diseases; particularly in the phyllosphere where this species is frequently found. To elucidate the molecular basis of the antifungal activity of M. pulcherrima, we compared a wildtype strain with a spontaneously occurring, pigmentless, weakly antagonistic mutant derivative. Whole genome sequencing of the wildtype and mutant strains identified a point mutation that creates a premature stop codon in the transcriptional regulator SNF2 in the mutant strain. Complementation of the mutant strain with the wildtype SNF2 gene restored pigmentation and recovered the strong antifungal activity. Mass spectrometry (UPLC HR HESI-MS) proved the presence of the pulcherrimin precursors cyclo(Leu-Leu) and pulcherriminic acid and identified new precursor and degradation products of pulcherriminic acid and/or pulcherrimin. All of these compounds were identified in the wildtype and complemented strain, but were undetectable in the pigmentless snf2 mutant strain. These results thus identify Snf2 as a regulator of antifungal activity and pulcherriminic acid biosynthesis in M. pulcherrima and provide a starting point for deciphering the molecular functions underlying the antagonistic activity of this yeast.

ORGANISM(S): Metschnikowia pulcherrima

PROVIDER: GSE128386 | GEO | 2019/09/01

REPOSITORIES: GEO

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Project description:6-Nonadecynoic acid (6-NDA), a plant-derived acetylenic acid, exhibits strong inhibitory activity against the human fungal pathogens Candida albicans, Aspergillus fumigatus, and Trichophyton mentagrophytes. In the present study, transcriptional profiling coupled with mutant and biochemical analyses were conducted using the model organism Saccharomyces cerevisiae to investigate the mechanism of action of this compound. 6-NDA elicited a transcriptome response indicative of fatty acid stress, altering the expression of genes known to be affected when yeast cells are grown in the presence of oleate. Mutants of S. cerevisiae lacking transcription factors that regulate fatty acid ?-oxidation showed increased sensitivity to 6-NDA. Fatty acid profile analysis indicated that 6-NDA inhibited the formation of fatty acids longer than 14 carbons in length. In addition, the growth inhibitory effect of 6-NDA was rescued in the presence of exogenously supplied oleate. To investigate the response of a pathogenic fungal species to 6-NDA, transcriptional profiling and biochemical analyses were also conducted in C. albicans. The transcriptional response and fatty acid profile of C. albicans were comparable to those obtained in S. cerevisiae, and the rescue of growth inhibition with exogenous oleate was also observed in C. albicans. In addition, 6-NDA enhanced the potency of the antifungal drug fluconazole in a fluconazole-resistant clinical isolate of C. albicans. Collectively, our results indicate that the antifungal activity of 6-NDA is mediated by a disruption in fatty acid homeostasis, and that this compound has potential utility in combination therapy in the treatment of drug-resistant fungal infections. Cultures of S. cerevisiae strain S288C were started at OD600 of 0.1, allowed to grow to OD600 of 0.2, then treated with either DMSO (0.25%) or 6-NDA at the IC50 concentration (2.2 ug/ml). When OD600 of 0.5 was reached, cells were harvested and frozen. Two biological replicate cultures were grown for each treatment, and RNA from each replicate was hybridized to 2 independent arrays, resulting in 4 hybridizations for each treatment. Cultures of C. albicans strain SC5314 were started at OD600 of 0.1, allowed to grow to OD600 of 0.2, then treated with either DMSO (0.25%) or 6-NDA at the IC50 concentration (4 ug/ml). When OD600 of 0.5 was reached, cells were harvested and frozen. Three biological replicate cultures were grown for each treatment, and RNA from each replicate was hybridized as dye-swap pairs, resulting in 6 hybridizations for each treatment.

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RNA-seq analysis of wt Metschnikowia pulcherrima cells and a spontaneous mutant (W8) in the snf2 gene that exhibited differential expression of the recently described pulcherrimin genes

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