Identification and refinement of two strong constitutive promoters for gene expression system of Schizosaccharomyces pombe

Fission yeast Schizosaccharomyces pombe shares various important properties with higher eukaryotes and is now considered a useful host for elevated production of mammalian proteins for medicinal applications. The full-length nmt1 promoter has been widely used as a strong promoter in S. pombe expression system. In the present study, the promoters of the eno101 and gpd3 genes in S. pombe were identified as strong constitutive promoters. For convenient applications in the plasmids of S. pombe, these promoters were refined to 276-bp eno and 273-bp gpd promoters by deleting undesired sequences and examining the expression of reporter genes including lacZ and xynA. Both the refined eno and gpd promoters provided approximately 1.5-fold higher expression of LacZ than nmt1 promoter. Furthermore, gene expression under the control of the eno or gpd promoter was not repressed by the components of YES medium while nmt1 promoter was inhibited by thiamine in yeast extract. Therefore, both eno and gpd promoters offer opportunities for efficient production of recombinant proteins by S. pombe in high cell-density fermentation.     

The green fluorescent protein gene functions as a reporter of gene expression in Phanerochaete chrysosporium

The enhanced green fluorescent protein (GFP) gene (egfp) was used as a reporter of gene expression driven by the glyceraldehyde-p-dehydrogenase (gpd) gene promoter and the manganese peroxidase isozyme 1 (mnp1) gene promoter in Phanerochaete chrysosporium. Four different constructs were prepared. pUGGM3' and pUGiGM3' contain the P. chrysosporium gpd promoter fused upstream of the egfp coding region, and pUMGM3' and pUMiGM3' contain the P. chrysosporium mnp1 promoter fused upstream of the egfp gene. In all constructs, the egfp gene was followed by the mnp1 gene 3' untranslated region. In pUGGM3' and pUMGM3', the promoters were fused directly with egfp, whereas in pUGiGM3' and pUMiGM3', following the promoters, the first exon (6 bp), the first intron (55 bp), and part of the second exon (9 bp) of the gpd gene were inserted at the 5' end of the egfp gene. All constructs were ligated into a plasmid containing the ura1 gene of Schizophyllum commune as a selectable marker and were used to transform a Ural1 auxotrophic strain of P. chrysosporium to prototrophy. Crude cell extracts were examined for GFP fluorescence, and where appropriate, the extracellular fluid was examined for MnP activity. The transformants containing a construct with an intron 5' of the egfp gene (pUGiGM3' and pUMiGM3') exhibited maximal fluorescence under the appropriate conditions. The transformants containing constructs with no introns exhibited minimal or no fluorescence. Northern (RNA) blots indicated that the insertion of a 5' intron resulted in more egfp RNA than was found in transformants carrying an intronless egfp. These results suggest that the presence of a 5' intron affects the expression of the egfp gene in P. chrysosporium. The expression of GFP in the transformants carrying pUMiGM3' paralled the expression of endogenous mnp with respect to nitrogen and Mn levels, suggesting that this construct will be useful in studying cis-acting elements in the mnp1 gene promoter.     

启动子替代构建糙皮侧耳漆酶高产菌株

POXC是糙皮侧耳合成最多的一种漆酶。应用启动子替代技术,用构巢曲霉的甘油醛-3-磷酸脱氢酶基因（gpd）启动子替代POXC基因的启动子,构建了超量表达POXC糙皮侧耳转化子。转化子中POXC基因表达量比出发菌株提高了0.72–3倍。在PDA平板培养、PD摇瓶培养和棉籽壳试管培养条件下,转化子漆酶活力显著提高,比出发菌株提高了1.5倍以上。用棉籽壳栽培,转化子菇产量比出发菌株提高了16.2%,培养料中木质素含量比出发菌株减少21%。结果表明,应用高效启动子替代能够显著提高糙皮侧耳漆酶基因的表达量、漆酶活力及其木质纤维素降解能力。     

A reliable transformation method and heterologous expression of beta-glucuronidase in Lentinula edodes

A simple and reliable mushroom transformation procedure based on electroporation of basidiospores or mycelial fragments was developed. This method eliminated the problem of protoplast preparation, the transformation efficiency were 30-150 transformants per mug DNA and the hygromycin resistant marker gene and gus were expressed in Lentinula edodes successfully. No false positive antibiotic-resistant cultures were detected by PCR amplification and the beta-glucuronidase (GUS) expression was maintained stable during mitotic cell division without selection pressure for more than 6 months. Southern analysis of transformants indicated the integration of gene might occur by non-homologous recombination. Using the glyceraldehyde-3-phosphate dehydrogenase (gpd) promoter with the first intron of gpd gene, the average GUS activity in L. edodes reached 144.6+/-3.9 U mg(-1) soluble protein, while only 30.1+/-0.7 U mg(-1) soluble protein was detected for those without the intron. The percentage of GUS in total soluble protein was 5.67 x 10(-4) (0.06%) for the transformant with the highest GUS activity. This rapid and convenient electroporation procedure offers a new approach for the genetic manipulation and tool to tag genes of important edible mushroom species.     

Heterologous expression of Zygosaccharomyces rouxii glycerol 3-phosphate dehydrogenase gene (ZrGPD1) and glycerol dehydrogenase gene (ZrGCY1) in Saccharomyces cerevisiae

We examined the effects of heterologous expression of the open reading frames (ORF) of two genes on salt tolerance and glycerol production in a Saccharomyces cerevisiae strain deficient in glycerol synthesis (gpd1Deltagpd2Delta). When the ORF of the Zygosaccharomyces rouxii glycerol 3-phosphate dehydrogenase gene (ZrGPD1) was expressed under the control of the GAL10 promoter, salt tolerance and glycerol production increased; when the ORF of the glycerol dehydrogenase gene (ZrGCY1) was expressed under the control of the GAL1 promoter, no such changes were observed. Zrgcy1p had a weak effect on glycerol production. These results suggest that Zrgpd1p is the primary enzyme involved in Z. rouxii glycerol production, following a mechanism similar to that of S. cerevisiae (Gpd1p). When the ORFs of the S. cerevisiae glycerol 3-phosphatase gene (GPP2) and ZrGPD1 were simultaneously expressed, glycerol production increased, compared with that in yeast expressing only ZrGPD1.     

IFN regulatory factor family members differentially regulate the expression of type III IFN (IFN-lambda) genes

Virus replication induces the expression of antiviral type I (IFN-alphabeta) and type III (IFN-lambda1-3 or IL-28A/B and IL-29) IFN genes via TLR-dependent and -independent pathways. Although type III IFNs differ genetically from type I IFNs, their similar biological antiviral functions suggest that their expression is regulated in a similar fashion. Structural and functional characterization of the IFN-lambda1 and IFN-lambda3 gene promoters revealed them to be similar to IFN-beta and IFN-alpha genes, respectively. Both of these promoters had functional IFN-stimulated response element and NF-kappaB binding sites. The binding of IFN regulatory factors (IRF) to type III IFN promoter IFN-stimulated response element sites was the most important event regulating the expression of these genes. Ectopic expression of the components of TLR7 (MyD88 plus IRF1/IRF7), TLR3 (Toll/IL-1R domain-containing adapter-inducing factor), or retinoic acid-inducible gene I (RIG-I) signal transduction pathways induced the activation of IFN-lambda1 promoter, whereas the IFN-lambda3 promoter was efficiently activated only by overexpression of MyD88 and IRF7. The ectopic expression of Pin1, a recently identified suppressor for IRF3-dependent antiviral response, decreased the IFN promoter activation induced by any of these three signal transduction pathways, including the MyD88-dependent one. To conclude, the data suggest that the IFN-lambda1 gene is regulated by virus-activated IRF3 and IRF7, thus resembling that of the IFN-beta gene, whereas IFN-lambda2/3 gene expression is mainly controlled by IRF7, thus resembling those of IFN-alpha genes.     

Cloning and sequence analysis of the glyceraldehyde-3-phosphate dehydrogenase gene from the zygomycetes fungus Rhizomucor miehei

Rhizomucor miehei is important from a biotechnological aspect in consequence of its content of aspartic proteinase, which has high milk-clotting activity. A genomic library of R. miehei NRRL 5901 has been constructed in a phage (Lambda Fix II) vector. The glyceraldehyde-3-phosphate dehydrogenase (gpd) gene was isolated from this library by hybridization of the recombinant phage clones with a gpd-specific gene probe generated by polymerase chain reaction. The complete nucleotide sequence encodes a putative polypeptide chain of 336 amino acids interrupted by 5 introns. The predicted amino acid sequence of this gene shows a high degree of sequence similarity to the glyceraldehyde-3-phosphate dehydrogenase proteins from yeast and filamentous fungi. The promoter region, containing a consensus TATA box, and 246-bp downstream from the putative stop codon were also determined. The possibility of using the gpd promoter in the construction of new transformation vectors is discussed.     

Genetic transformation of the filamentous yeast, Trichosporon cutaneum, using dominant selection markers

An efficient transformation system for the filamentous yeast, Trichosporon cutaneum, has been developed. Transformation was obtained with plasmids carrying either the Escherichia coli hygromycin B phosphotransferase-encoding gene (hph) or the Streptoalloteichus hindustanus phleomycin-resistance gene (ble), as dominant selection markers. Expression of both resistance-conferring genes was controlled by the gpd promoter and the trpC terminator, from Aspergillus nidulans. The transformation frequency was up to 500 colonies/micrograms of transforming DNA, using the ble gene, and up to 100 colonies/micrograms of transforming DNA, using the hph gene. Co-transformation frequencies using unselected DNA varied between 50 and 65%. The transforming DNA was found to consist of multiple tandem plasmid copies of high Mr. This polymeric structure, in nonselective media, was mitotically unstable, possibly indicating that it existed in an episomal state.     

Homologous expression of recombinant lignin peroxidase in Phanerochaete chrysosporium

The glyceraldehyde-3-phosphate dehydrogenase (gpd) promoter was used to drive expression of lip2, the gene encoding lignin peroxidase (LiP) isozyme H8, in primary metabolic cultures of Phanerochaete chrysosporium. The expression vector, pUGL, also contained the Schizophyllum commune ura1 gene as a selectable marker. pUGL was used to transform a P. chrysosporium Ura11 auxotroph to prototrophy. Ura+ transformants were screened for peroxidase activity in liquid cultures containing high-carbon and high-nitrogen medium. Recombinant LiP (rLiP) was secreted in active form by the transformants after 4 days of growth, whereas endogenous lip genes were not expressed under these conditions. Approximately 2 mg of homogeneous rLiP/liter was obtained after purification. The molecular mass, pI, and optical absorption spectrum of rLiPH8 were essentially identical to those of the wild-type LiPh8 (wt LiPH8), indicating that heme insertion, folding, and secretion functioned normally in the transformant. Steady-state and transient-state kinetic properties for the oxidation of veratryl alcohol between wtLiPH8 and rLiPH8 were also identical.     

Efficient Transformation of the Astaxanthin-Producing Yeast Phaffia Rhodozyma

An efficient transformation system for the astaxanthin-producing yeast Phaffia rhodozyma was developed based on electroporation that routinely yields approximately 1000 transformants per g of plasmid DNA. The high transformation efficiency depends on vector integration in the ribosomal DNA (rDNA) and the presence of the homologous glycolytic glyceraldehyde-3-phosphate dehydrogenase (gpd) promoter and terminator to drive the expression of the transposon Tn5 encoded kanamycin resistance gene (Km^R) as a selective marker. Using this system stable transformants were obtained, carrying multiple plasmid copies. Plasmid copy number could be markedly increased by deletion of the gpd terminator from the transforming plasmid.     

Homologous expression of recombinant manganese peroxidase in Phanerochaete chrysosporium.

The promoter region of the glyceraldehyde-3-phosphate dehydrogenase gene (gpd) was used to drive expression of mnp1, the gene encoding Mn peroxidase isozyme 1, in primary metabolic cultures of Phanerochaete chrysosporium. A 1,100-bp fragment of the P. chrysosporium gpd promoter region was fused upstream of the mnp1 gene to construct plasmid pAGM1, which contained the Schizophyllum commune ade5 gene as a selectable marker. pAGM1 was used to transform a P. chrysosporium ade1 auxotroph to prototrophy. Ade+ transformants were screened for peroxidase activity on a solid medium containing high carbon and high nitrogen (2% glucose and 24 mM NH4 tartrate) and o-anisidine as the peroxidase substrate. Several transformants that expressed high peroxidase activities were purified and analyzed further in liquid cultures. Recombinant Mn peroxidase (rMnP) was expressed and secreted by transformant cultures on day 2 under primary metabolic growth conditions (high carbon and high nitrogen), whereas endogenous wild-type mnp genes were not expressed under these conditions. Expression of rMnP was not influenced by the level of Mn in the culture medium, as previously observed for the wild-type Mn peroxidase (wtMnP). The amount of active rMnP expressed and secreted in this system was comparable to the amount of enzyme expressed by the wild-type strain under ligninolytic conditions. rMnP was purified to homogeneity by using DEAE-Sepharose chromatography, Blue Agarose chromatography, and Mono Q column chromatography. The M(r) and absorption spectrum of rMnP were essentially identical to the M(r) and absorption spectrum of wtMnP, indicating that heme insertion, folding, and secretion were normal.(ABSTRACT TRUNCATED AT 250 WORDS)     

Gpd1 and Gpd2 fine-tuning for sustainable reduction of glycerol formation in Saccharomyces cerevisiae

Gpd1 and Gpd2 are the two isoforms of glycerol 3-phosphate dehydrogenase (GPDH), which is the rate-controlling enzyme of glycerol formation in Saccharomyces cerevisiae. The two isoenzymes play crucial roles in osmoregulation and redox balancing. Past approaches to increase ethanol yield at the cost of reduced glycerol yield have most often been based on deletion of either one or two isogenes (GPD1 and GPD2). While single deletions of GPD1 or GPD2 reduced glycerol formation only slightly, the gpd1Δ gpd2Δ double deletion strain produced zero glycerol but showed an osmosensitive phenotype and abolished anaerobic growth. Our current approach has sought to generate "intermediate" phenotypes by reducing both isoenzyme activities without abolishing them. To this end, the GPD1 promoter was replaced in a gpd2Δ background by two lower-strength TEF1 promoter mutants. In the same manner, the activity of the GPD2 promoter was reduced in a gpd1Δ background. The resulting strains were crossed to obtain different combinations of residual GPD1 and GPD2 expression levels. Among our engineered strains we identified four candidates showing improved ethanol yields compared to the wild type. In contrast to a gpd1Δ gpd2Δ double-deletion strain, these strains were able to completely ferment the sugars under quasi-anaerobic conditions in both minimal medium and during simultaneous saccharification and fermentation (SSF) of liquefied wheat mash (wheat liquefact). This result implies that our strains can tolerate the ethanol concentration at the end of the wheat liquefact SSF (up to 90 g liter(-1)). Moreover, a few of these strains showed no significant reduction in osmotic stress tolerance compared to the wild type.     

Cloning and sequence analysis of a glyceraldehyde-3-phosphate dehydrogenase gene from Ganoderma lucidum

A cDNA library of Ganoderma lucidum has been constructed using a Zap Express cloning vector. A glyceraldehyde-3-phosphate dehydrogenase gene (gpd) was isolated from this library by hybridization of the recombinant phage clones with a gpd-specific gene probe generated by PCR. By comparison of the cDNA and the genomic DNA sequences, it was found that the complete nucleotide sequence encodes a putative polypeptide chain of 338 amino acids interrupted by 6 introns. The predicted amino acid sequence of this gene shows a high degree of sequence similarity to the GPD proteins from yeast and filamentous fungi. The promoter region contains a CT-rich stretch, two CAAT boxes, and a consensus TATA box. The possibility of using the gpd promoter in the construction of new transformation vectors is discussed.