Project description:The recent discovery of a velvet complex containing several regulators of secondary metabolism in the model fungus Aspergillus nidulans raises the question whether similar type complexes direct fungal development in genera other than Aspergillus. Penicillium chrysogenum is the industrial producer of the antibiotic penicillin, whose biosynthetic regulation is barely understood. Here we provide a functional analysis of two major homologues of the velvet complex in P. chrysogenum, that we have named PcvelA and PclaeA. Data from array analysis using a ?PcvelA deletion strain indicate a significant role of PcvelA on the expression of biosynthesis and developmental genes, including PclaeA. Northern hybridization and HPLC quantifications of penicillin titres clearly show that both PcvelA and PclaeA play a major role in penicillin biosynthesis. Both regulators are further involved in different and distinct developmental processes. While PcvelA deletion leads to light independent conidial formation, dichotomous branching of hyphae and pellet formation in shaking cultures, a ?PclaeA strain shows a severe impairment in conidiophore formation in both the light and dark. Bimolecular fluorescence complementation assays finally provide evidence for a velvet-like complex in Penicillium chrysogenum, with structurally conserved components that have distinct developmental roles, illustrating the functional plasticity of these regulators within filamentous ascomycetes. Transcriptomes of PcvelA- and PclaeA- deletion mutants were compared with expression data from recipient strain deltaPcku70 and reference strain P2niaD18 as a control
Project description:The recent discovery of a velvet complex containing several regulators of secondary metabolism in the model fungus Aspergillus nidulans raises the question whether similar type complexes direct fungal development in genera other than Aspergillus. Penicillium chrysogenum is the industrial producer of the antibiotic penicillin, whose biosynthetic regulation is barely understood. Here we provide a functional analysis of two major homologues of the velvet complex in P. chrysogenum, that we have named PcvelA and PclaeA. Data from array analysis using a ΔPcvelA deletion strain indicate a significant role of PcvelA on the expression of biosynthesis and developmental genes, including PclaeA. Northern hybridization and HPLC quantifications of penicillin titres clearly show that both PcvelA and PclaeA play a major role in penicillin biosynthesis. Both regulators are further involved in different and distinct developmental processes. While PcvelA deletion leads to light independent conidial formation, dichotomous branching of hyphae and pellet formation in shaking cultures, a ΔPclaeA strain shows a severe impairment in conidiophore formation in both the light and dark. Bimolecular fluorescence complementation assays finally provide evidence for a velvet-like complex in Penicillium chrysogenum, with structurally conserved components that have distinct developmental roles, illustrating the functional plasticity of these regulators within filamentous ascomycetes.
Project description:Penicillium chrysogenum was successfully engineered to produce a novel carbamoylated cephalosporin that can be used as a synthon for semi-synthetic cephalosporins. To this end, structural genes for Acremonium chrysogenum expandase/hydroxylase and Streptomyces clavuligerus carbamoyltransferase were expressed in a penicillinG high-producing strain of P. chrysogenum. Growth of the engineered strain in the presence of the side-chain precursor adipic acid resulted in production of adipoyl-7-amino-3-carbamoyloxymethyl-3-cephem-4-carboxylic acid (ad7-ACCCA) and of several adipoylated pathway intermediates. A combinatorial chemostat-based transcriptome study, in which the ad7-ACCCA- producing strain and a strain lacking key genes in β-lactam synthesis were grown in the presence and absence of adipic acid, enabled the dissection of transcriptional responses to adipic acid per se and to ad7-ACCCA production. In chemostat cultures of both strains, adipic acid served as an additional carbon source. Transcriptome analysis supported an earlier proposal, based on 13C-labelling studies, that adipic acid catabolism in P. chrysogenum occurs via β-oxidation and enabled the identification of putative genes for enzymes involved in mitochondrial and peroxisomal β-oxidation pathways. Several of the genes that showed a specifically altered transcript level in ad7-ACCCA-producing cultures were previously implicated in oxidative stress responses. As strain improvement programmes lead to increased specific productivity and yields, a deeper understanding of these stress responses is likely to be important to also achieve high ad7-ACCCA titers with engineered strains of P. chrysogenum.
Project description:Targeting an engineered DNA fragment to a specific site in chromosomes in order to disrupt, overexpress or modify the nucleotide sequence of a gene requires homologous recombination repair mechanism. This DNA repair mechanism is not predominant in fungi, resulting in extremely low targeting efficiency. To increase this efficiency, it is becoming common practice to disable the non homologous end joining (NHEJ) pathway that causes random integration, by deleting homologous gene to human KU70 and KU80 which encode proteins functioning in the NHEJ pathway. These genes have been successfully deleted in several organisms, including the yeast Kluyveromyces lactis and the fungi Neurospora Crassa and several Aspergilli species. In this study we investigated the behavior of high penicillinG-producing Penicillium chrysogenum strains, in which the KU70 or KU80 homologues, HdfA or HdfB, had been deleted. Targeting efficiency in these mutant strains was significantly increased relative to the reference strain. Both physiological and transcriptome data of chemostat cultivations of the hdfA deletion strain and the reference strain showed minimal differences. However, in a direct competition experiment to assess global strain fitness, the reference strain had a clear advantage over the deletion strain. The full characterization of these recombinant host strains is an essential step to guide the future construction of a whole genome knock-out mutant collection.
Project description:Industrial production of penicillin G by Penicillium chrysogenum requires medium supplementation with the side chain precursor phenylacetate. However, P.chrysogenum grown in presence of phenylalanine as sole nitrogen source formed detectable extracellular amounts of phenylacetate and penicillin G. To get more insights in the metabolism implicated, chemostat-cultivation in presence of 13C9-phenylalanine were carried out. Quantification and modeling of the labeled metabolite pools indicated that phenylalanine was i) incorporated in nascent protein, ii) transaminated to phenylpyruvate and further converted by oxidation or by decarboxylation and iii) oxidized into tyrosine and subsequently assimilated in the homogentisate pathway. Comparative transcriptome analysis of phenylalanine and (NH4)2SO4 grown P.chrysogenum cultures enabled to identify two putative 2-oxo acid decarboxylases Pc13g9300 and Pc18g01490. Both cDNAs were cloned and expressed in the decarboxylase-free Saccharomyces cerevisiae CEN.PK711-7C (pdc1delta, 5delta, 6delta, aro10delta, thi3delta) strain that has lost the ability to grow on glucose as sole carbon source or on phenylalanine as sole nitrogen source. Only Pc13g09300 was able to restore growth on glucose and on phenylalanine, demonstrating that this gene encodes a dual substrate pyruvate, phenylpyruvate decarboxylase. This newly identified thiamine-dependent 2-oxo acid decarboxylase provides clues to explain the formation of phenylacetate via an Ehrlich-like pathway in P.chrysogenum. Penicillium chrysogenum DS17690 was grown in aerobic glucose limited chemostat at 25oC, pH 6.5 and a dilution rate of 0.03h-1 with either amonia or phenylalanine