Developmentally regulated proteases from the basidiomycete Schizophyllum commune

Comparative Proteomics Study on the Postharvest Senescence of Volvariella volvacea

Volvariella volvacea is difficult to store after harvest, which restricts the production and circulation of V. volvacea fruiting bodies. Low-temperature storage is the traditional storage method used for most edible fungi. However, V. volvacea undergoes autolysis at low temperatures. When fruiting bodies are stored at 15 °C (suitable temperature), V. volvacea achieves the best fresh-keeping effect. However, the molecular mechanism underlying the postharvest senescence of V. volvacea remains unclear. Based on this information, we stored V. volvacea fruiting bodies at 15 °C after harvest and then analyzed the texture and phenotype combined with the results of previous physiological research. Four time points (0, 24, 60, and 96 h) were selected for the comparative proteomics study of V. volvacea during storage at 15 °C. A variety of proteins showed differential expressions in postharvest V. volvacea at 15 °C. Further comparison of the gene ontology (GO) enrichment analysis and KEGG pathways performed at different sampling points revealed proteins that were significantly enriched at several time points. At the same time, we also analyzed differentially expressed proteins (DEPs) related to the RNA transport, fatty acid biosynthesis and metabolism, and amino acid biosynthesis and metabolism pathways, and discussed the molecular functions of the PAB1, RPG1, ACC1, ADH3, ADH2, ALD5, and SDH2 proteins in postharvest V. volvacea senescence. Our results showed that many biological processes of the postharvest senescence of V. volvacea changed. Most importantly, we found that most RNA transport-related proteins were down-regulated, which may lead to a decrease in related gene regulation. Our results also showed that the expression of other important proteins, such as the fatty acid metabolism related proteins increased; and changes in fatty acid composition affected the cell membrane, which may accelerate the ripening and perception of V. volvacea fruiting bodies. Therefore, our research provides a reference for further studies on the aging mechanism of V. volvacea.

Identification of transcripts up-regulated in asexual and sexual fruiting bodies of the Dutch elm disease pathogen Ophiostoma novo-ulmi

Suppression subtractive hybridization cDNA libraries were prepared from asexual synnemata (S-lib) and sexual perithecia (P-lib) fruiting bodies of the Dutch elm disease pathogen Ophiostoma novo-ulmi subsp. novo-ulmi isolate H327 (mating-type MAT1-1) consisting of 630 and 401 cDNA clones, respectively. Both libraries were differentially screened in duplicate with forward and reverse subtracted probes. Up-regulated S-lib transcripts included those with homologies to phosphoenolpyruvate carboxykinase and aquaporin. Up-regulated P-lib transcripts included those with homologies to aspartyl proteinase, DNA lyase 2, and part of a mating-type (MAT) protein containing a DNA-binding domain of the high-mobility group (HMG) type. Phylogenetic analyses of HMG domains present within the putative O. novo-ulmi MAT protein and within MAT1-1-3 and MAT1-2-1 proteins of other ascomycete fungi identified the O. novo-ulmi protein as a homologue of the MAT1-1-3 protein, which represents part of the so far uncharacterized O. novo-ulmi MAT1-1 idiomorph. Reverse transcription - quantitative real-time PCR indicated up-regulation of the MAT1-1-3 homologue in O. novo-ulmi perithecia and synnemata. The present work identifies, for the first time, proteins involved in the formation of asexual and sexual fruiting bodies in O. novo-ulmi and should be of interest to researchers concerned with reproduction, mating type, and sexuality of filamentous ascomycete fungi.

Purification, properties and developmental regulation of a Ca(2+)-independent serine-cysteine protease from Allomyces arbuscula

Reproductive differentiation in Allomyces takes place against the background of substrate limitation, a sharp increase in intracellular proteolysine and the induction of at least one specific protease. The aim of this report is to describe the purification, properties and developmental regulation of this enzyme. The enzyme has been partially purified by a combination of ion exchange chromatography, ultrogel filtration and affinity chromatography. The purified enzyme in SDS-PAGE appeared as a doublet of M(r) 40-43 kDa. Two bands corresponding to a relative molecular mass of 40-43 kDa were also apparent in activity gels. The protein has an apparent molecular mass in the region of 43 kDa as estimated by gel filtration. The enzyme therefore, seems to be a monomer of 43 kDa. The second band in SDS-PAGE and activity gels is probably the proteolyzed form of the enzyme. The protease recognized alanine and to a lesser extent phenylalanine in the P1 position when assayed with a range of synthetic peptides. The active site of the enzyme contains a reactive serine residue, as shown by its inhibition with PMSF and soya bean trypsin inhibitor. There is probably a reactive cysteine residue as well since the enzyme activity is strongly inhibited by HgCl2, a thiol group binding reagent. The enzyme is present in zoospores but disappears progressively during germination and hyphal growth. It reappears when actively growing cultures are transferred to dilute salt solution. In conclusion, we have purified a serine-cysteine protease of M(r) 43 kDa. This enzyme has a very restricted substrate specificity and appears to be developmentally regulated.

Multiple acid proteinases in the cellular slime mould Dictyostelium discoideum

Proteinase activity in the cellular slime mould Dictyostelium discoideum has been analyzed by electrophoresis on polyacrylamide gels containing denatured hemoglobin. At least eight bands due to acid proteinases have been defined using extracts of myxamoebae, four bands A-D which move faster than the fifth and major band E, a minor band E' which moves just behind E and two slow bands G and H. Fruiting body formation was accompanied by the appearance of one new proteinase band F. The proteinases were present in extracts of both axenically-grown and bacterially-grown cells. Differences between the pH dependence and stability of the individual proteinases were detected. Inhibitor studies suggested that the faster proteinases A-D may be cathepsin B-like, whilst the slower enzymes E, E' and F do not fit readily into any known group of proteinases since they were sensitive to HgCl2 but not to other inhibitors of cathepsin B and not to inhibitors of cathepsin D-like proteinases under standard conditions. None of the proteinases was apparently formed during or after preparation of extracts and the proteinases could be re-run on polyacrylamide gels to give only the band expected from the first run. The bands are believed to reflect multiple proteinase activities within the cell.