The potential of Pseudozyma yeastlike epiphytes for the production of heterologous recombinant proteins

Identification of the gene PaEMT1 for biosynthesis of mannosylerythritol lipids in the basidiomycetous yeast Pseudozyma antarctica

The yeast Pseudozyma antarctica produces a large amount of glycolipid biosurfactants known as mannosylerythritol lipids (MELs), which show not only excellent surface-active properties but also versatile biochemical actions. To investigate the biosynthesis of MELs in the yeast, we recently reported expressed sequence tag (EST) analysis and estimated genes expressing under MEL production conditions. Among the genes, a contiguous sequence of 938 bp, PA_004, showed high sequence identity to the gene emt1, encoding an erythritol/mannose transferase of Ustilago maydis, which is essential for MEL biosynthesis. The predicted translation product of the extended PA_004 containing the two introns and a stop codon was aligned with Emt1 of U. maydis. The predicted amino acid sequence shared high identity (72%) with Emt1 of U. maydis, although the amino-terminal was incomplete. To identify the gene as PaEMT1 encoding an erythritol/mannose transferase of P. antarctica, the gene-disrupted strain was developed by the method for targeted gene disruption, using hygromycin B resistance as the selection marker. The obtained ΔPaEMT1 strain failed to produce MELs, while its growth was the same as that of the parental strain. The additional mannosylerythritol into culture allowed ΔPaEMT1 strain to form MELs regardless of the carbon source supplied, indicating a defect of the erythritol/mannose transferase activity. Furthermore, we found that MEL formation is associated with the morphology and low-temperature tolerance of the yeast.

Expression and purification of active recombinant equine lysozyme in Escherichia coli

Equine lysozyme (EL) is a calcium (Ca)-binding lysozyme and is an intermediary link between non-Ca-binding C-type lysozyme and alpha-lactalbumin. The feature of lysozymes to assemble into the fibrils has recently gained considerable attention for the investigation of the functional properties of these proteins. To study the structural and functional properties of EL, a synthetic gene was cloned and EL was overexpressed in Escherichia coli as a fused protein. The His-tagged recombinant EL was accumulated as inclusion bodies. Up to 50 mg/l of the recombinant EL could be achieved after purification by Ni(2+) affinity chromatography, refolding in the presence of arginine, CM-Sepharose column purification following TEV protease cleavage. The purified protein was functionally active, as determined by the lysozyme activity, proving the proper folding of protein. The purified lysozyme was used for the oligomerisation studies. The protein formed amyloid fibrils during incubation in acidic pH and elevated temperature. The recombinant EL forms two types of fibrils: ring shaped and linear, similar to the native EL.

Convenient transformation of anamorphic basidiomycetous yeasts belonging to genus pseudozyma induced by electroporation

A convenient procedure for carrying out transformation by electroporation was optimized for the genus Pseudozyma. Successful transformation was achieved using a plasmid, pUXV1, that confers resistance to hygromycin B; the maximum transformation efficiency was 48 transformants/mug of plasmid DNA. Transformants of Pseudozyma antarctica T-34 expressing a green fluorescent protein were obtained by the procedure.

Alternative methods for genetic transformation of Pseudozyma antarctica, a basidiomycetous yeast-like fungus

Electroporation and Agrobacterium tumefaciens-mediated transformation (ATMT) were adapted and optimized for genetic transformation of the basidiomycetous yeast-like fungus Pseudozyma antarctica as alternatives to the cumbersome PEG/CaCl(2)-mediated transformation of protoplasts. Electroporation yielded 100-200 transformants per mug of DNA per 10(8) cells after 3 days on selective medium. For its part, ATMT yielded 60-160 transformants per 10(6) input cfu after 5-10 days on a selective medium. Transformants obtained from both methods showed stable hygromycin resistance and strong expression of green fluorescent protein. Analysis of integration events revealed a limited number of predominantly tandem insertions in the genome of transformants, an improvement over PEG/CaCl(2)-mediated transformation. Both protocols relied on intact conidia of P. antarctica as starting material and thus eliminated the need for cell wall-degrading or weakening agents such as lytic enzymes or chemicals. Other advantages over protoplast transformation included higher yield of transformants and shorter recovery time of transformed colonies on selective medium.

Cloning of the glyceraldehyde-3-phosphate dehydrogenase gene from Pseudozyma flocculosa and functionality of its promoter in two Pseudozyma species

Pseudozyma flocculosa is a yeast-like epiphyte recently classified as a basidiomycete related to the Ustilaginales. In this study, we report the cloning of its gene coding for a putative glyceraldehyde-3-phosphate dehydrogenase (GPD). This gene was selected on the premise that its transcripts are abundant during the growth phase of P. flocculosa. The complete sequence of this gene was found to contain two introns in the coding region and one in the 3'-untranslated region. This gene was present in a single copy in the genome of P. flocculosa. By comparing its deduced amino acid sequence with various sequences from basidiomycetous and ascomycetous fungi, we observed a stronger homology with the former group as predicted by the new classification of P. flocculosa. The promoter region lacked a typical TATA or CAAT box but contained a CT-rich region including the transcription start site. Although the GPD promoter showed a stronger affinity within P. flocculosa, it remained active across species as shown by expressing the green fluorescent protein in Pseudozyma antarctica. The cloning of this gene and its promoter brings new and versatile options to the limited genetic tools currently available for the study of the recently defined Pseudozyma genus.

The Pseudozyma flocculosa actin promoter allows the strong expression of a recombinant protein in the Pseudozyma species

Fungi belonging to the recently classified genus Pseudozyma possess some unique properties such as biocontrol activity, production of rare antimicrobial glycolipids and production of recombinant proteins. In this work, we report the first cloning of a promoter endogenous to the multi-faceted yeast-like Pseudozyma flocculosa, that of the actin gene. The promoter region lacked typical TATA or CAAT box but displayed three putative GC box and two CT-rich regions. As in other related basidiomycetes, only one copy of the actin gene was present in the genome of P. flocculosa. The activity of the actin promoter was compared to that of the HSP70 promoter from Ustilago maydis in two Pseudozyma species. In P. flocculosa, the actin promoter allowed the expression of a very high amount of GFP protein (27.8 mg g(-1) total protein) compared to those obtained with the HSP70 promoter in liquid culture. By contrast, the levels of GFP expression obtained in liquid culture were similar with the actin or the HSP70 promoter in Pseudozyma antarctica. A similar pattern of GFP expression was observed in solid culture. The cloning of this new promoter offers a unique genetic tool to further exploit and study the unusual properties of fungi from the Pseudozyma genus.