Project description:Histone posttranslational modifications (HPTMs) are involved in regulating the synthesis of fungal bioactive compounds. The exact molecular mechanisms of the silencing/activation of secondary metabolism (SM) clusters by these epigenetic events however are not yet fully understood. This work applies a combined approach of quantitative mass spectrometry (LC-MS/MS) and chromatin immunoprecipitation coupled with massive parallel sequencing (ChIP-seq) to identify the chromatin landscape in two metabolic states: primary and secondary metabolism. Furthermore, to link the particular chromatin states to the expression of condition specific genes, genome wide transcriptome (RNA-seq) was performed. Strikingly, we found that silent A. nidulans SM clusters are free of repressive H3K9me3 though this heterochromatic mark forms distinguished peaks flanking the many SM clusters. In addition, silent SM clusters do not contain detectable levels of activating histone marks such as H3K4me3, H3K36me3 or H3Ac, which, to some extent, are established upon activation of the clusters. In order to investigate the function of dynamic H3K4 methylation/demethylation in transcription, we characterized the KdmB- Jarid1 family histone demethylase. The in vitro assay using heterologously expressed KdmB showed that it is an active demethylase; moreover, MS/MS as well ChIP-seq approaches revealed that it targets H3K4me3 in vivo mediating transcriptional repression. KdmB positively regulates the expression of 40% of A. nidulans SM genes and this function appears to be independent of its demethylase activity. Our bioinformatics approach revealed two states of H3K4me3 in A. nidulans genome: loci with low levels of this mark are more disposed to differential expression in response to environmental clues, while the genes marked by high H3K4me3 levels are constitutively transcribed in our experimental conditions. Taken together our data reveal important role of H3K4 methylation/demethylation in transcription regulation. Furthermore, this study presents the first genome-wide map of H3K4me3, H3K9me3, H3K36me3 and H3Ac in A. nidulans in different metabolic conditions. Two strains, wild type and kdmB deletion, at two conditions, growth at primary (17h) and secondary (48h), were analysed. Each sample was replicated.

Project description:Histone posttranslational modifications (HPTMs) are involved in regulating the synthesis of fungal bioactive compounds. The exact molecular mechanisms of the silencing/activation of secondary metabolism (SM) clusters by these epigenetic events however are not yet fully understood. This work applies a combined approach of quantitative mass spectrometry (LC-MS/MS) and chromatin immunoprecipitation coupled with massive parallel sequencing (ChIP-seq) to identify the chromatin landscape in two metabolic states: primary and secondary metabolism. Furthermore, to link the particular chromatin states to the expression of condition specific genes, genome wide transcriptome (RNA-seq) was performed. Strikingly, we found that silent A. nidulans SM clusters are free of repressive H3K9me3 though this heterochromatic mark forms distinguished peaks flanking the many SM clusters. In addition, silent SM clusters do not contain detectable levels of activating histone marks such as H3K4me3, H3K36me3 or H3Ac, which, to some extent, are established upon activation of the clusters. In order to investigate the function of dynamic H3K4 methylation/demethylation in transcription, we characterized the KdmB- Jarid1 family histone demethylase. The in vitro assay using heterologously expressed KdmB showed that it is an active demethylase; moreover, MS/MS as well ChIP-seq approaches revealed that it targets H3K4me3 in vivo mediating transcriptional repression. KdmB positively regulates the expression of 40% of A. nidulans SM genes and this function appears to be independent of its demethylase activity. Our bioinformatics approach revealed two states of H3K4me3 in A. nidulans genome: loci with low levels of this mark are more disposed to differential expression in response to environmental clues, while the genes marked by high H3K4me3 levels are constitutively transcribed in our experimental conditions. Taken together our data reveal important role of H3K4 methylation/demethylation in transcription regulation. Furthermore, this study presents the first genome-wide map of H3K4me3, H3K9me3, H3K36me3 and H3Ac in A. nidulans in different metabolic conditions.

Project description:The filamentous fungus Aspergillus nidulans has been a primary workhorse used to understand fungal genetics. Much of this work has focused on elucidating the genetics of biosynthetic gene clusters (BGCs) and the secondary metabolites (SMs) they produce. SMs are both niche defining in fungi and of great economic importance to humans. Despite the focus on A. nidulans, very little is known about the natural diversity in secondary metabolism within this species. We determined the BGC content and looked for evolutionary patterns in BGCs from whole-genome sequences of two clinical isolates and the A4 reference genome of A. nidulans Differences in BGC content were used to explain SM profiles determined using liquid chromatography-high-resolution mass spectrometry. We found that in addition to genetic variation of BGCs contained by all isolates, nine BGCs varied by presence/absence. We discovered the viridicatumtoxin BGC in A. nidulans and suggest that this BGC has undergone a horizontal gene transfer from the Aspergillus section Nigri lineage into Penicillium sometime after the sections Nigri and Nidulantes diverged. We identified the production of viridicatumtoxin and several other compounds previously not known to be produced by A. nidulans One isolate showed a lack of sterigmatocystin production even though it contained an apparently intact sterigmatocystin BGC, raising questions about other genes and processes known to regulate this BGC. Altogether, our work uncovers a large degree of intraspecies diversity in BGC and SM production in this genetic model species and offers new avenues to understand the evolution and regulation of secondary metabolism.IMPORTANCE Much of what we know about the genetics underlying secondary metabolite (SM) production and the function of SMs in the model fungus Aspergillus nidulans comes from a single reference genome. A growing body of research indicates the importance of biosynthetic gene cluster (BGC) and SM diversity within a species. However, there is no information about the natural diversity of secondary metabolism in A. nidulans We discovered six novel clusters that contribute to the considerable variation in both BGC content and SM production within A. nidulans We characterize a diverse set of mutations and emphasize how findings of single nucleotide polymorphisms (SNPs), deletions, and differences in evolutionary history encompass much of the variation observed in nonmodel systems. Our results emphasize that A. nidulans may also be a strong model to use within-species diversity to elucidate regulatory cross talk, fungal ecology, and drug discovery systems.

Dataset Information

KdmA, a histone H3 demethylase with bipartite function, differentially regulates primary and secondary metabolism in Aspergillus nidulans.

Publications

KdmA, a histone H3 demethylase with bipartite function, differentially regulates primary and secondary metabolism in Aspergillus nidulans.

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