Project description:Reconstruction of signaling networks regulating fungal morphogenesis by the expression profiling of wild-type and the temperature sensitive morphological ramosa-1 mutant.
Project description:Reconstruction of signaling networks regulating fungal morphogenesis by the expression profiling of wild-type and the temperature sensitive morphological ramosa-1 mutant. Aspergillus niger wildtype versus Ramosa mutant for 1h at 37 under controlled growth condition in 5L bioreactor
Project description:Pitkanen2014 - Metabolic reconstruction of Aspergillus niger using CoReCo
This model was reconstructed with the CoReCo method (Comparative ReConstruction of genome-scale metabolic networks) from protein sequence and phylogeny data.
This model is described in the article:
Comparative Genome-Scale Reconstruction of Gapless Metabolic Networks for Present and Ancestral Species
Esa Pitkänen, Paula Jouhten, Jian Hou, Muhammad Fahad Syed, Peter Blomberg, Jana Kludas, Merja Oja, Liisa Holm, Merja Penttilä, Juho Rousu, Mikko Arvas
PLoS Comput Biol. 2014 Feb 6;10(2):e1003465
Abstract:
We introduce a novel computational approach, CoReCo, for comparative metabolic reconstruction and provide genome-scale metabolic network models for 49 important fungal species. Leveraging on the exponential growth in sequenced genome availability, our method reconstructs genome-scale gapless metabolic networks simultaneously for a large number of species by integrating sequence data in a probabilistic framework. High reconstruction accuracy is demonstrated by comparisons to the well-curated Saccharomyces cerevisiae consensus model and large-scale knock-out experiments. Our comparative approach is particularly useful in scenarios where the quality of available sequence data is lacking, and when reconstructing evolutionary distant species. Moreover, the reconstructed networks are fully carbon mapped, allowing their use in 13C flux analysis. We demonstrate the functionality and usability of the reconstructed fungal models with computational steady-state biomass production experiment, as these fungi include some of the most important production organisms in industrial biotechnology. In contrast to many existing reconstruction techniques, only minimal manual effort is required before the reconstructed models are usable in flux balance experiments. CoReCo is available at http://esaskar.github.io/CoReCo/.
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Project description:Saprotrophic fungi, such as Aspergillus niger, grow as mycelial colonies that are often considered uniform entities. To test this uniformity, we analyzed pie-slice sections of a colony grown on spatially separated substrates (glucose, wheat bran, sugar beet pulp) using transcriptomics, proteomics and metabolomics. The colony tuned its response to the local carbon source composition. Plant biomass degrading CAZymes and intracellular carbon catabolic enzymes were more abundant in parts of the colony containing the corresponding sugars. For example a stronger pectinolytic response was observed in the part of the colony grown on the pectin-rich sugar beet pulp. Our results argue against a situation in which small molecules are transported efficiently through the colony and favour high diversity within the fungal colony in natural biotopes, where the substrate is typically heterogeneous. It also demonstrates the high level of plasticity of A. niger in reponse to the composition of the prevailing lignocellulose.
Project description:Filamentous fungi are confronted with changes and limitations of their carbon source during growth in their natural habitats and during industrial applications. To survive life-threatening starvation conditions, carbon from extra- and intracellular resources becomes mobilized to fuel fungal self-propagation. Key to understand the underlying cellular processes is the system-wide analysis of fungal starvation responses in a temporal and spatial resolution. The knowledge deduced is important for the development of optimized industrial production processes. This study describes the physiological, morphological and genome-wide transcriptional changes caused by prolonged carbon starvation during submerged batch cultivation of the filamentous fungus Aspergillus niger. Bioreactor cultivation supported highly reproducible growth conditions and monitoring of physiological parameters. Changes in hyphal growth and morphology were analyzed at distinct cultivation phases using automated image analysis. The Affymetrix GeneChip platform was used to establish genome-wide transcriptional profiles for three selected time points during prolonged carbon starvation. Compared to the exponential growth transcriptome, about 50% (7,292) of all genes displayed differential genes expression during at least one of the starvation time points. Enrichment analysis of Gene Ontology, Pfam domain and KEGG pathway annotations uncovered autophagy and asexual reproduction as major global transcriptional trends. Induced transcription of genes encoding hydrolytic enzymes was accompanied by increased secretion of hydrolases including chitinases, glucanases, proteases and phospholipases as identified by mass spectrometry. This study is the first system-wide analysis of the carbon starvation response in a filamentous fungus. Morphological, transcriptomic and secretomic analyses identified key events important for fungal survival and their chronology. The dataset obtained forms a comprehensive framework for further elucidation of the interrelation and interplay of the individual cellular events involved.
Project description:RacA is the main Rho GTPase in Aspergillus niger regulating polarity maintenance via controlling actin dynamics. We have previously shown that both deletion and dominant activation of RacA (RacG18V) provoke an actin localization defect and thereby loss of polarized tip extension. This loss of apical dominance results in frequent dichotomous branching in the racA deletion strain and an apolar growing phenotype for RacG18V. In the current study we investigated the transcriptomics and physiological consequences of these morphological changes and compared the data with our previously established morphogenetic network model for the dichotomous branching mutant ramosa-1. This integrated approach revealed that polar tip growth is most likely orchestrated by the concerted activities of phospholipid signaling, sphingolipid signaling, TORC2 signaling, calcium signaling and CWI signaling pathways. The transcriptomic signatures and the reconstructed network model for all three morphology mutants imply that these pathways become integrated to bring about different physiological adaptations including changes in sterol, zinc and amino acid metabolism and changes in ion transport and protein trafficking. We furthermore followed that fate of exocytotic (SncA) and endocytotic (AbpA, SlaB) markers in the dichotomous branching racA deletion mutant, and provide data demonstrating that hyperbranching does not per se result in increased protein secretion.
Project description:Filamentous fungi are confronted with changes and limitations of their carbon source during growth in their natural habitats and during industrial applications. To survive life-threatening starvation conditions, carbon from extra- and intracellular resources becomes mobilized to fuel fungal self-propagation. Key to understand the underlying cellular processes is the system-wide analysis of fungal starvation responses in a temporal and spatial resolution. The knowledge deduced is important for the development of optimized industrial production processes. This study describes the physiological, morphological and genome-wide transcriptional changes caused by prolonged carbon starvation during submerged batch cultivation of the filamentous fungus Aspergillus niger. Bioreactor cultivation supported highly reproducible growth conditions and monitoring of physiological parameters. Changes in hyphal growth and morphology were analyzed at distinct cultivation phases using automated image analysis. The Affymetrix GeneChip platform was used to establish genome-wide transcriptional profiles for three selected time points during prolonged carbon starvation. Compared to the exponential growth transcriptome, about 50% (7,292) of all genes displayed differential genes expression during at least one of the starvation time points. Enrichment analysis of Gene Ontology, Pfam domain and KEGG pathway annotations uncovered autophagy and asexual reproduction as major global transcriptional trends. Induced transcription of genes encoding hydrolytic enzymes was accompanied by increased secretion of hydrolases including chitinases, glucanases, proteases and phospholipases as identified by mass spectrometry. This study is the first system-wide analysis of the carbon starvation response in a filamentous fungus. Morphological, transcriptomic and secretomic analyses identified key events important for fungal survival and their chronology. The dataset obtained forms a comprehensive framework for further elucidation of the interrelation and interplay of the individual cellular events involved. for each post-exponential time point (Day1, Day3 and Day6 post-carbon depletion), biological duplicates were performed.
Project description:Co-expression networks have recently emerged as a useful approach for updating and improving gene annotation at a near-genome level. This is based on the hypothesis that function can be inferred by delineating transcriptional networks in which a gene of interest is embedded. In this study, we generated a co-expression network for the filamentous cell factory Aspergillus niger from 128 RNA-seq experiments. We confirm that over 70% of the >14,000 A. niger genes are represented in this network and show that gene functions can be accurately predicted as evidenced by analysis of various control sub-networks. Our analyses further indicate that this RNA-seq co-expression network has a higher predictive power compared to the microarray co-expression network that we published in 2019. To demonstrate the potential of the new co-expression network to unveil complex and non-intuitive predictions for gene regulation phenomena, we provide here new insights into the temporal, spatial and metabolic expression profile that connects a secreted antifungal peptide with mycelial growth, asexual development, secondary metabolism and pectin degradation in A. niger. To empower biologists to generate or apply co-expression networks in the fungal kingdom and beyond, we also demonstrate that (i) high quality networks can be generated from only 32 transcriptional experiments; (ii) such low numbers of experiments can be safely compensated for by using higher thresholds for defining co-expression pairs; and (iii) a ’safety in numbers’ rule applies, whereby experimental conditions have minimal impact on network content provided a certain number of experiments are included.
Project description:The full genome sequencing of the filamentous fungi Aspergillus nidulans, Aspergillus niger and Aspergillus oryzae has opened the possibilities for studying the cellular physiology of these fungi on a systemic level. As a tool to explore this, we are presenting an Affymetrix GeneChip developed for transcriptome analysis of any of the three above-mentioned aspergilli. Transcriptome analysis of triplicate batch cultivations of all three aspergilli on glucose-and xylose media has been performed, and used to validate the performance of the micro array. By doing gene comparisons of all three species, and cross-analysing this with the expression data, 23 genes, including the xylose transcriptional activator XlnR, have been identified to be a conserved response across the Aspergillus sp. Promoter analysis of the upregulated genes in all three species suggest the XlnR-binding site to be 5’-GGNTAAA-3’. We are thus presenting a validated tool for transcription analysis of three Aspergillus species and a methodology for comparative transcriptomics. Keywords: Physiological response
Project description:RacA is the main Rho GTPase in Aspergillus niger regulating polarity maintenance via controlling actin dynamics. We have previously shown that both deletion and dominant activation of RacA (RacG18V) provoke an actin localization defect and thereby loss of polarized tip extension. This loss of apical dominance results in frequent dichotomous branching in the racA deletion strain and an apolar growing phenotype for RacG18V. In the current study we investigated the transcriptomics and physiological consequences of these morphological changes and compared the data with our previously established morphogenetic network model for the dichotomous branching mutant ramosa-1. This integrated approach revealed that polar tip growth is most likely orchestrated by the concerted activities of phospholipid signaling, sphingolipid signaling, TORC2 signaling, calcium signaling and CWI signaling pathways. The transcriptomic signatures and the reconstructed network model for all three morphology mutants imply that these pathways become integrated to bring about different physiological adaptations including changes in sterol, zinc and amino acid metabolism and changes in ion transport and protein trafficking. We furthermore followed that fate of exocytotic (SncA) and endocytotic (AbpA, SlaB) markers in the dichotomous branching racA deletion mutant, and provide data demonstrating that hyperbranching does not per se result in increased protein secretion. This data set consists of 14 samples in total and covers the genome-wide transcriptional responses of Aspergillus niger towards deletion of racA and expression of a dominant active racA allele (G18V). The genome-wide transcriptional effect of deleting racA was monitored by comparison with the A. niger wild type. For both, the racA deletion mutant and the wild type, samples consist of biological triplicates (6 in total). The genome-wide transcriptional effect of expressing the dominant active racA mutant allele was monitored by sampling 2 and 4 hours after induction with maltose. For comparison, the racA wild type allele was induced and expressed similarly and samples were taken at corresponding time points. The experimental setup for the dominant active racA expression consisted of biological triplicates (8 in total).