At a time when the notion of microorganisms did not exist, our ancestors empirically established methods for the production of various fermentation foods: miso (bean curd seasoning) and shoyu (soy sauce), both of which have been widely used and are essential for Japanese cooking, and sake, a magical alcoholic drink consumed at a variety of ritual occasions, are typical examples. A filamentous fungus, Aspergillus oryzae, is the key organism in the production of all these traditional foods, and its solid-state cultivation (SSC) has been confirmed to be the secret for the high productivity of secretory hydrolases vital for the fermentation process. Indeed, our genome comparison and transcriptome analysis uncovered mechanisms for effective degradation of raw materials in SSC: the extracellular hydrolase genes that have been found only in the A. oryzae genome but not in A. fumigatus are highly induced during SSC but not in liquid cultivation. Also, the temperature reduction process empirically adopted in the traditional soy-sauce fermentation processes has been found to be important to keep strong expression of the A. oryzae-specific extracellular hydrolases. One of the prominent potentials of A. oryzae is that it has been successfully applied to effective degradation of biodegradable plastic. Both cutinase, responsible for the degradation of plastic, and hydrophobin, which recruits cutinase on the hydrophobic surface to enhance degradation, have been discovered in A. oryzae. Genomic analysis in concert with traditional knowledge and technology will continue to be powerful tools in the future exploration of A. oryzae.
Indole-diterpenes represented by paxilline share a common pentacyclic core skeleton derived from indole and geranylgeranyl diphosphate. To shed light on the detailed biosynthetic mechanism of the paspaline-type hexacyclic skeleton, we examined the reconstitution of paxilline biosynthetic machinery in Aspergillus oryzae NSAR1. Stepwise introduction of the six pax genes enabled us to isolate all biosynthetic intermediates and to synthesize paxilline. In vitro and in vivo studies on the key enzymes, prenyltransferase PaxC and cyclase PaxB, allowed us to elucidate actual substrates of these enzymes. Using the isolated and the synthesized epoxide substrates, the highly intriguing stepwide epoxidation/cyclization mechanism for the construction of core structure has been confirmed. In addition, we also demonstrated "tandem transformation" to simultaneously introduce two genes using a single vector (paxG/paxB, pAdeA; paxP/paxQ, pUNA). This may provide further option for the reconstitution strategy to synthesize more complex fungal metabolites.
Exogenous thiamine regulates Aspergillus oryzae thiA, which is involved in thiamine synthesis. One of the two introns in its 5P P-untranslated region (5P P-UTR) contains motifs (regions A and B) highly conserved among fungal thiamine biosynthesis genes. Deletion of either region relieved the repression by thiamine and thiamine inhibited intron splicing, suggesting that regions A and B are required for e⁄cient splicing. Furthermore, transcript splicing was essential for thiA gene expression. These observations suggest a novel gene expression regulatory mechanism in ¢lamentous fungi, in which exogenous thiamine controls intron splicing to regulate gene expression. Interestingly, regions A and B constitute a part of a thiamine pyrophosphate-binding riboswitch-like domain that has been quite recently found in the 5P P-UTR of thiA.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.