Project description:Diverse expression patterns for secondary metabolism gene clusters from Aspergillus flavus under different environmental conditions and in genetic mutants: Insights into regulation of cyclopiazonic acid along with aflatoxin Species of Aspergillus produce a diverse array of secondary metabolites, and recent genomic analysis predicts that these species have the capacity to synthesize many more compounds. It has been possible to infer the presence of 55 gene clusters associated with secondary metabolism in A. flavus. Presumably, secondary metabolites play important roles in the ecology of the producing species, but functions for most secondary metabolites remain unknown. Only three metabolic pathways have been associated with the predicted clusters in A. flavus. These include aflatoxin, cyclopiazonic acid (CPA), and aflatrem. To gain insight into the regulation of, and infer ecological significance for the 55 secondary metabolite gene clusters predicted in A. flavus, we examined their expression over 28 diverse conditions. Variables included culture media and temperature, fungal development, colonization of developing maize seeds, and misexpression of laeA, the global regulator of secondary metabolism. Hierarchical clustering analysis of expression profiles allowed us to categorize the gene clusters into four distinct clades. Gene clusters for the production of aflatoxins, CPA, and seven other unknown compound(s) were identified as belonging to one clade. To further explore the relationships found by gene expression analysis, aflatoxin and CPA production were quantified under five different cell culture environments known to be conducive or non-conducive for aflatoxin biosynthesis and during colonization of developing maize seeds. Results from these studies showed that secondary metabolism gene clusters have distinctive gene expression profiles. Aflatoxin and CPA were found to have unique regulation but similar enough that they would be expected to co-occur in commodities colonized with A. flavus.
Project description:Mining of fungal genomes uncovered their great potential for the production of novel secondary metabolites (SMs). However most of them stay silent under standard laboratory cultivation conditions. Co-cultivation of fungi with organism that occur in their natural habitat has shown to be trigger for the activation of such silent SM gene clusters. Recently, we showed that the cultivation of Aspergillus nidulans with the bacterium Streptomyces rapamycinicus leads to the activation of the orsellinic acid gene cluster. Hence we decided to study this interaction further to gain insight into the regulation of SM gene clusters and more specifically to study the chromatin remodelling network actuve upon co-cultivation of the two organisms. This study gives novel insight into the regulation of the orsellinic acid gene cluster and the interaction of the two organisms. To the best of our knowledge this is the first report of mapping the chromatin landscape of microbial interactions, making this study a role model for the analysis of similar systems.
Project description:Drosophila melanogaster larvae and filamentous fungi both utilise organic material. Here they compete for resources. Filamentous fungi can defend themselves and their substrate from predation respectively competition by the production and excretion of secondary metabolites, including substances with antibiotic and insecticidal properties. To analyse the traits that enables D. melanogaster larvae to reduce the harmful effects of fungal secondary metabolites and to develop on fungal infested substrate we confronted larvae with a toxin-producing wild type of Aspergillus nidulans, with a toxin-production-impaired mutant strain of A. nidulans, and with sterigmatocystin, a highly toxic metabolite of A. nidulans. Early first instar larvae were transferred to breeding substrate inhabited by fungal colonies respectively inoculated with the purified mycotoxin or controls. After 3, 6, 12, and 24 hours of confrontation larvae were collected and samples prepared for whole transcriptome shotgun sequencing.
Project description:Histone modifications have been shown to be crucial for secondary metabolism in various filamentous fungi. Here we studied the influence of histone acetylation on secondary metabolite production in the phytopathogenic fungus Fusarium fujikuroi, a known producer of several secondary metabolites including pigments and mycotoxins. Deletion of the classical HDACs FfHdF1, FfHdF2 and FfHdF3 indicated that FfHdF1 and FfHdF2 are major regulators of secondary metabolism, whereas FfHdF3 is involved in developmental processes but dispensable for secondary metabolite production in F. fujikuroi. Microarray analysis with the major HDAC FfHdF2 revealed differential regulation of several secondary metabolite gene clusters, subsequently verified by a combination of chemical and biological approaches. These results indicate that HDACs are responsible for gene silencing but also gene activation. Chromatin immunoprecipitation assays with M-NM-^TffhdF2 revealed significant alterations regarding the acetylation state in the landscape of secondary metabolite gene clusters thereby providing insights into the regulatory mechanism. In addition, the class I HDAC FfHdF1 also has major impact on secondary metabolism in F. fujikuroi. Furthermore, deletion of both ffhdF1 and ffhdF2 resulted in de-repression of secondary metabolites under normally repressing conditions. Thus, manipulation of HDAC encoding genes might provide a powerful tool for the activation of cryptic secondary metabolites. Investigation of whole genome gene expression of the Fusarium fujikuroi wild type IMI58289, M-NM-^TffhdF2 mutant under nitrogen starvation and nitrogen sufficient conditions. In this study we hybridized in total 12 microarrays using total RNA recovered from a wild-type culture of F. fujikuroi IMI58289 and M-NM-^TffhdF2 mutant culture. All cultures were grown on a 6 mM Gln (10%) and a 60 mM Gln medium (100%). For each combination of culture and medium a biological replicate was created. Each chip measures the expression level of 14,397 genes from F. fujikuroi IMI58289 with eight 60-mer probes.
Project description:The filamentous fungus Aspergillus terreus is known to produce both industrially and pharmaceutically important secondary metabolites. The objective of this study is to investigate the effect of exogenously added butyrolactone I (BI) on the submerged culture of A. terreus, especially on the possible regulation of the secondary metabolism on the transcriptional level. In order to elucidate the presumed regulative role of butyrolactone I, a large-scale microarray gene expression study was designed and conducted with an industrially utilised A. terreus strain MUCL38669. A. terreus MUCL38669 was cultured in secondary metabolism inducing submerged conditions for nine days, where butyrolactone I was added at the beginning of the growth phase (at 24 hours p.i.), in the middle of the growth phase (at 96 hours p.i.) or in the late growth phase (at 120 hours p.i.), in addition to the control culture where no exogenous butyrolactone I was added. To obtain comprehensive gene expression profiles over the whole culture time, samples were taken at six time points: 24 hours, 48 hours, 96 hours, 120 hours, 144 hours and 216 hours post inoculation.
Project description:Light is a major environmental signal regulating many different biological processes. In Aspergillus nidulans light controls asexual and sexual development as well as the production of secondary metabolites. In order to get a global view of genes regulated during asexual development and of genes involved in other light-regulated biological processes, a genome-wide approach was undertaken. Total RNA was isolated from surface-grown, developmentally competent mycelia of the wild-type strain FGSC4 exposed to white light (11 W/m2) for 30 minutes or grown in the dark, labelled, and hybridized to a spotted microarray of A. nidulans.