Regulation of salt tolerance by Torulaspora delbrueckii calcineurin target Crz1p

Recently, the academic interest in the yeast Torulaspora delbrueckii has increased notably due to its high resistance to several types of stress, including salt and osmotic imbalance. However, the molecular mechanisms underlying these unusual properties are poorly understood. In Saccharomyces cerevisiae, the high-salt response is mediated by calcineurin, a conserved Ca(2+)/calmodulin-modulated protein phosphatase that regulates the transcriptional factor Crz1p. Here, we cloned the T. delbrueckii TdCRZ1 gene, which encodes a putative zinc finger transcription factor homologue to Crz1p. Consistent with this, overexpression of TdCRZ1 enhanced the salt tolerance of S. cerevisiae wild-type cells and suppressed the sensitivity phenotype of cnb1Delta and crz1Delta mutants to monovalent and divalent cations. However, T. delbrueckii cells lacking TdCrz1p showed phenotypes distinct from those previously observed in S. cerevisiae crz1Delta mutants. Quite remarkably, Tdcrz1-null cells were insensitive to high Na(+) and were more Li(+) tolerant than wild-type cells. Clearly, TdCrz1p was not required for the salt-induced transcriptional activation of the TdENA1 gene, encoding a putative P-type ATPase homologue to the main S. cerevisiae Na(+) pump ENA1. Furthermore, T. delbrueckii cells were insensitive to the immunosuppressive agents FK506 and cyclosporine A, both in the presence and in the absence of NaCl. Signaling through the calcineurin/Crz1 pathway appeared to be essential only on high-Ca(2+)/Mn(2+) media. Hence, T. delbrueckii and S. cerevisiae differ in the regulatory circuits and mechanisms that drive the adaptive response to salt stress.

The BAR domain proteins: molding membranes in fission, fusion, and phagy

The Bin1/amphiphysin/Rvs167 (BAR) domain proteins are a ubiquitous protein family. Genes encoding members of this family have not yet been found in the genomes of prokaryotes, but within eukaryotes, BAR domain proteins are found universally from unicellular eukaryotes such as yeast through to plants, insects, and vertebrates. BAR domain proteins share an N-terminal BAR domain with a high propensity to adopt alpha-helical structure and engage in coiled-coil interactions with other proteins. BAR domain proteins are implicated in processes as fundamental and diverse as fission of synaptic vesicles, cell polarity, endocytosis, regulation of the actin cytoskeleton, transcriptional repression, cell-cell fusion, signal transduction, apoptosis, secretory vesicle fusion, excitation-contraction coupling, learning and memory, tissue differentiation, ion flux across membranes, and tumor suppression. What has been lacking is a molecular understanding of the role of the BAR domain protein in each process. The three-dimensional structure of the BAR domain has now been determined and valuable insight has been gained in understanding the interactions of BAR domains with membranes. The cellular roles of BAR domain proteins, characterized over the past decade in cells as distinct as yeasts, neurons, and myocytes, can now be understood in terms of a fundamental molecular function of all BAR domain proteins: to sense membrane curvature, to bind GTPases, and to mold a diversity of cellular membranes.

Loss of P4 ATPases Drs2p and Dnf3p disrupts aminophospholipid transport and asymmetry in yeast post-Golgi secretory vesicles

Eukaryotic plasma membranes generally display asymmetric lipid distributions with the aminophospholipids concentrated in the cytosolic leaflet. This arrangement is maintained by aminophospholipid translocases (APLTs) that use ATP hydrolysis to flip phosphatidylserine (PS) and phosphatidylethanolamine (PE) from the external to the cytosolic leaflet. The identity of APLTs has not been established, but prime candidates are members of the P4 subfamily of P-type ATPases. Removal of P4 ATPases Dnf1p and Dnf2p from budding yeast abolishes inward translocation of 6-[(7-nitrobenz-2-oxa-1,3-diazol-4-yl)aminocaproyl] (NBD)-labeled PS, PE, and phosphatidylcholine (PC) across the plasma membrane and causes cell surface exposure of endogenous PE. Here, we show that yeast post-Golgi secretory vesicles (SVs) contain a translocase activity that flips NBD-PS, NBD-PE, and NBD-PC to the cytosolic leaflet. This activity is independent of Dnf1p and Dnf2p but requires two other P4 ATPases, Drs2p and Dnf3p, that reside primarily in the trans-Golgi network. Moreover, SVs have an asymmetric PE arrangement that is lost upon removal of Drs2p and Dnf3p. Our results indicate that aminophospholipid asymmetry is created when membrane flows through the Golgi and that P4-ATPases are essential for this process.

Actin-based motility during endocytosis in budding yeast

Actin assembly nucleated by Arp2/3 complex has been implicated in the formation and movement of endocytic vesicles. The dendritic nucleation model has been proposed to account for Arp2/3-mediated actin assembly and movement. Here, we explored the model by examining the role of capping protein in vivo, with quantitative tracking analysis of fluorescence markers for different stages of endocytosis in yeast. Capping protein was most important for the initial movement of endocytic vesicles away from the plasma membrane, which presumably corresponds to vesicle scission and release. The next phase of endosome movement away from the plasma membrane was also affected, but less so. The results are consistent with the dendritic nucleation model's prediction of capping protein as important for efficient actin assembly and force production. In contrast, the movement of late-stage endocytic vesicles, traveling through the cytoplasm en route to the vacuole, did not depend on capping protein. The movement of these vesicles was found previously to depend on Lsb6, a WASp interactor, whereas Lsb6 was found here to be dispensable for early endosome movement. Thus, the molecular requirements for Arp2/3-based actin assembly differ in early versus later stages of endocytosis. Finally, acute loss of actin cables led to increased patch motility.

Using budding yeast to screen for anti-prion drugs

Prions are misfolded proteins capable of propagating their altered conformation which are commonly considered as the causative agent of transmissible spongiform encephalopathies, a class of fatal neurodegenerative diseases. Currently, no treatment for prion-based diseases is available. Recently we have developed a rapid, yeast-based, two-step assay to screen for anti-prion drugs [1]. This new method allowed us to identify several compounds that are effective in vivo against budding yeast [PSI+] and [URE3] prions but also able to promote mammalian prion clearance in three different cell culture-based assays. Taken together, these results validate our method as an economic and efficient high-throughput screening approach to identify novel prion inhibitors or to carry on comprehensive structure-activity studies for already isolated anti-mammalian prion drugs. These results suggest furthermore that biochemical pathways controlling prion formation and/or maintenance are conserved from yeast to human and thus amenable to pharmacological and genetic analysis. Finally, it would be very interesting to test active drugs isolated using the yeast-based assay in models for other diseases (neurodegenerative or not) involving amyloid fibers like Huntington's, Parkinson's or Alzheimer's diseases.

Debaryomyces hansenii — an extremophilic yeast with biotechnological potential

We illuminate the ecological, physiological and genetic characteristics of the yeast Debaryomyces hansenii in the view of our belief that this metabolically versatile, non-pathogenic, osmotolerant and oleaginous microorganism represents an attractive target for fundamental and applied biotechnological research. To this end, we give a broad overview of extant biotechnological procedures using D. hansenii, e.g. in the manufacture of various foods, and propose research into the heterologous synthesis of a range of fine chemicals.

DhARO4, an amino acid biosynthetic gene, is stimulated by high salinity inDebaryomyces hansenii

The highly halotolerant yeast Debaryomyces hansenii when grown in the presence of 2M NaCl, increased the expression of ARO4 which is involved in the biosynthesis of aromatic amino acids. The function of the isolated gene was verified by complementation of a Saccharomyces cerevisiae null mutant, aro4Delta, restoring the specific activity of the enzyme (a 3-deoxy-D-arabino-heptulosonate-7-phosphate synthase) to wild-type levels. DhARO4 transcript expression under high salinity was stimulated at the beginning of the exponential growth phase. As the DhARO4 promoter region presents putative GCRE and CRE sequences, its expression was evaluated under conditions of NaCl stress and amino acid starvation, showing similar expression levels for either condition. The combined effect of both stressors resulted in a further increase in transcript levels over the singly added stressors, indicating independent stimulatory events. Our results support the hypothesis that high salinity and amino acid availability are physiologically interconnected.

Subcellular localization of the cyclin dependent kinase inhibitor Sic1 is modulated by the carbon source in budding yeast

The cyclin dependent kinase inhibitor Sic1 and the cyclin Clb5 are essential regulators of the cyclin dependent kinase Cdc28 during the G1 to S transition in budding yeast. Yeast enters S phase after ubiquitin-mediated degradation of Sic1, an event triggered by Cln1, 2-Cdc28 mediated phosphorylation. We recently showed that Sic1 is involved in carbon source modulation of the critical cell size required to enter S phase. Here we show that the amount and sub-cellular localization of Sic1 are also carbon source-modulated. We identify a bipartite nuclear localization sequence responsible for nuclear localization of Sic1 and for correct cell cycle progression in a carbon-source dependent manner. Similarly to Cip/Kip proteins-Sic1 mammalian counterparts-Sic1 facilitates nuclear accumulation of its cognate cyclin, since cytoplasmic building-up of Clb5 is observed upon switching off expression of the SIC1 gene. Our data indicate a previously unrecognized inhibitor/activator dual role for Sic1 and put it among key molecules whose activity is regulated by their nuclear-cytoplasmic localization.

Role of the Hog1 stress-activated protein kinase in the global transcriptional response to stress in the fungal pathogen Candida albicans

The resistance of Candida albicans to many stresses is dependent on the stress-activated protein kinase (SAPK) Hog1. Hence we have explored the role of Hog1 in the regulation of transcriptional responses to stress. DNA microarrays were used to characterize the global transcriptional responses of HOG1 and hog1 cells to three stress conditions that activate the Hog1 SAPK: osmotic stress, oxidative stress, and heavy metal stress. This revealed both stress-specific transcriptional responses and a core transcriptional response to stress in C. albicans. The core transcriptional response was characterized by a subset of genes that responded in a stereotypical manner to all of the stresses analyzed. Inactivation of HOG1 significantly attenuated transcriptional responses to osmotic and heavy metal stresses, but not to oxidative stress, and this was reflected in the role of Hog1 in the regulation of C. albicans core stress genes. Instead, the Cap1 transcription factor plays a key role in the oxidative stress regulation of C. albicans core stress genes. Our data show that the SAPK network in C. albicans has diverged from corresponding networks in model yeasts and that the C. albicans SAPK pathway functions in parallel with other pathways to regulate the core transcriptional response to stress.

Toward a molecular interpretation of the surface stress theory for yeast morphogenesis

The surface stress theory was proposed more than twenty years ago to explain morphogenesis of walled organisms. This theory makes simple assumptions on the force that drives microbial growth and how a cell's response to this force generates shape. This classic formulation may now be explained in more detailed molecular terms due to recent advances in the study of yeast morphogenesis with respect to the mechanism of cell polarization, the fine tuning of polarized growth to allocate necessary components to proper locations, and the local and global responses to turgor that provide control over the location and duration of growth.

Oxylipin covered ascospores of Eremothecium coryli

Eremothecium coryli is known to produce intriguing spindle-shaped ascospores with long and thin whip-like appendages. Here, ultra structural studies using scanning electron microscopy, indicate that these appendages serve to coil around themselves and around ascospores causing spore aggregation. Furthermore, using immunofluorescence confocal laser scanning microscopy it was found that hydrophobic 3-hydroxy oxylipins cover the surfaces of these ascospores. Using gas chromatography-mass spectrometry, only the oxylipin 3-hydroxy 9:1 (a monounsaturated fatty acid containing a hydroxyl group on carbon 3) could be identified. Sequential digital imaging suggests that oxylipin-coated spindle-shaped ascospores are released from enclosed asci probably by protruding through an already disintegrating ascus wall.

Metabolic engineering of the purine pathway for riboflavin production in Ashbya gossypii

Purine nucleotides are essential precursors for living organisms because they are involved in many important processes, such as nucleic acid synthesis, energy supply, and the biosynthesis of several amino acids and vitamins such as riboflavin. GTP is the immediate precursor for riboflavin biosynthesis, and its formation through the purine pathway is subject to several regulatory mechanisms in different steps. Extracellular purines repress the transcription of most genes required for de novo ATP and GTP synthesis. Additionally, three enzymes of the pathway, phosphoribosyl pyrophosphate (PRPP) amidotransferase, adenylosuccinate synthetase, and IMP dehydrogenase, are subject to feedback inhibition by their end products. Here we report the characterization and manipulation of the committed step in the purine pathway of the riboflavin overproducer Ashbya gossypii. We report that phosphoribosylamine biosynthesis in A. gossypii is negatively regulated at the transcriptional level by extracellular adenine. Furthermore, we show that ATP and GTP exert a strong inhibitory effect on the PRPP amidotransferase from A. gossypii. We constitutively overexpressed the AgADE4 gene encoding PRPP amidotransferase in A. gossypii, thereby abolishing the adenine-mediated transcriptional repression. In addition, we replaced the corresponding residues (aspartic acid310, lysine333, and alanine417) that have been described to be important for PRPP amidotransferase feedback inhibition in other organisms by site-directed mutagenesis. With these manipulations, we managed to enhance metabolic flow through the purine pathway and to increase the production of riboflavin in the triple mutant strain 10-fold (228 mg/liter).

Yeast kinetochore microtubule dynamics analyzed by high-resolution three-dimensional microscopy

We have probed single kinetochore microtubule (k-MT) dynamics in budding yeast in the G1 phase of the cell cycle by automated tracking of a green fluorescent protein tag placed proximal to the centromere on chromosome IV and of a green fluorescent protein tag fused to the spindle pole body protein Spc42p. Our method reliably distinguishes between different dynamics in wild-type and mutant strains and under different experimental conditions. Using our methods we established that in budding yeast, unlike in metazoans, chromosomes make dynamic attachments to microtubules in G1. This makes it possible to interpret measurements of centromere tag dynamics as reflecting k-MT dynamics. We have examined the sensitivity of our assay by studying the effect of temperature, exposure to benomyl, and a tubulin mutation on k-MT dynamics. We have found that lowering the temperature and exposing cells to benomyl attenuate k-MT dynamics in a similar manner. We further observe that, in contrast to previous reports, the mutant tub2-150 forms k-MTs that depolymerize faster than wild type. Based on these findings, we propose high-resolution light microscopy of centromere dynamics in G1 yeast cells as a sensitive assay for the regulation of single k-MT dynamics.

Arp10p is a pointed-end-associated component of yeast dynactin

In metazoans, dynein-dependent vesicle transport is mediated by dynactin, containing an actin-related protein, Arp1p, together with a cargo-selection complex containing a second actin-related protein, Arp11. Paradoxically, in budding yeast, models of dynactin function imply an interaction with membranes, whereas the lack of microtubule-based vesicle transport implies the absence of a cargo-selection complex. Using both genetic and biochemical approaches, we demonstrate that Arp10p is the functional yeast homologue of Arp11, suggesting the possible existence of a pointed-end complex in yeast. Specifically, Arp10p interacts with Arp1p and other dynactin subunits and is dependent on Arp1p for stability. Conversely, Arp10p stabilizes the dynactin complex by association with the Arp1p filament pointed end. Using a novel hRAS-Arp1p one-hybrid assay, we show that Arp1p associates with the plasma membrane dependent on dynactin subunits, but independent of dynein, and sensitive to cell wall damage. We directly show the association of Arp1p with not only the plasma membrane but also with a less dense membrane fraction. Based on the hRAS-Arp1p assay, loss of Arp10p enhances the apparent association of dynactin with the plasma membrane and suppresses the loss of signaling conferred by cell wall damage.

Controlled formation of volatile components in cider making using a combination of Saccharomyces cerevisiae and Hanseniaspora valbyensis yeast species

The effect of pure and mixed fermentation by Saccharomyces cerevisiae and Hanseniaspora valbyensis on the formation of major volatile components in cider was investigated. When the interaction between yeast strains of S. cerevisiae and H. valbyensis was studied, it was found that the two strains each affected the cell growth of the other upon inoculation of S. cerevisiae during growth of H. valbyensis. The effects of pure and mixed cultures of S. cerevisiae and H. valbyensis on alcohol fermentation and major volatile compound formation in cider were assessed. S. cerevisiae showed a conversion of sugar to alcohol of 11.5%, while H. valbyensis produced alcohol with a conversion not exceeding 6%. Higher concentrations of ethyl acetate and phenethyl acetate were obtained with H. valbyensis, and higher concentrations of isoamyl alcohol and isobutyl were formed by S. cerevisiae. Consequently, a combination of these two yeast species in sequential fermentation was used to increase the concentration of ethyl esters by 7.41-20.96%, and to decrease the alcohol concentration by 25.06-51.38%. Efficient control of the formation of volatile compounds was achieved by adjusting the inoculation time of the two yeasts.

The changes of catechins during the fermentation of green tea

The dynamics of tea catechins and organic acids in fermented fluid and yeast cells were studied. The concentration of eight kinds of catechins solution decreased by from 29.6% to 47.6%, respectively, some catechins were absorbed and accumulated by yeast cells, but the amount in the cells was very low during the fermentation process. The investigation of catechins resolved in four citrate buffers with a pH range of 2.6-5.6 for 18 h showed that most catechins were stable in buffer solutions of pH 4.6 and 5.6, and significant losses took place in solutions of pH 2.6 and 3.6. However, most catechins were released and recovered by adjusting the pH value to 5.6, which suggested that catechins in extremely acidic buffer solutions might reversibly combine each other or with other compounds.

From function to shape: a novel role of a formin in morphogenesis of the fungus Ashbya gossypii

Morphogenesis of filamentous ascomycetes includes continuously elongating hyphae, frequently emerging lateral branches, and, under certain circumstances, symmetrically dividing hyphal tips. We identified the formin AgBni1p of the model fungus Ashbya gossypii as an essential factor in these processes. AgBni1p is an essential protein apparently lacking functional overlaps with the two additional A. gossypii formins that are nonessential. Agbni1 null mutants fail to develop hyphae and instead expand to potato-shaped giant cells, which lack actin cables and thus tip-directed transport of secretory vesicles. Consistent with the essential role in hyphal development, AgBni1p locates to tips, but not to septa. The presence of a diaphanous autoregulatory domain (DAD) indicates that the activation of AgBni1p depends on Rho-type GTPases. Deletion of this domain, which should render AgBni1p constitutively active, completely changes the branching pattern of young hyphae. New axes of polarity are no longer established subapically (lateral branching) but by symmetric divisions of hyphal tips (tip splitting). In wild-type hyphae, tip splitting is induced much later and only at much higher elongation speed. When GTP-locked Rho-type GTPases were tested, only the young hyphae with mutated AgCdc42p split at their tips, similar to the DAD deletion mutant. Two-hybrid experiments confirmed that AgBni1p interacts with GTP-bound AgCdc42p. These data suggest a pathway for transforming one axis into two new axes of polar growth, in which an increased activation of AgBni1p by a pulse of activated AgCdc42p stimulates additional actin cable formation and tip-directed vesicle transport, thus enlarging and ultimately splitting the polarity site.

Secondary structure probing of the human RNase MRP RNA reveals the potential for MRP RNA subsets

RNase MRP is a ribonucleoprotein endoribonuclease involved in eukaryotic pre-rRNA processing. The enzyme possesses an RNA subunit, structurally related to that of RNase P RNA, that is thought to be catalytic. RNase MRP RNA sequences from Saccharomycetaceae species are structurally well defined through detailed phylogenetic and structural analysis. In contrast, higher eukaryote MRP RNA structure models are based on comparative sequence analysis of only five sequences and limited probing data. Detailed structural analysis of the Homo sapiens MRP RNA, entailing enzymatic and chemical probing, is reported. The data are consistent with the phylogenetic secondary structure model and demonstrate unequivocally that higher eukaryote MRP RNA structure differs significantly from that reported for Saccharomycetaceae species. Neither model can account for all of the known MRP RNAs and we thus propose the evolution of at least two subsets of RNase MRP secondary structure, differing predominantly in the predicted specificity domain.

Debaryomyces hansenii, a highly osmo-tolerant and halo-tolerant yeast, maintains activated Dhog1p in the cytoplasm during its growth under severe osmotic stress

The HOG pathway is an important mitogen-activated protein kinase (MAPK) signal transduction pathway in Saccharomyces cerevisiae that mediates adaptation of cells to hyper-osmotic stress. Activation of this pathway causes rapid but transient, phosphorylation of the MAPK Hog1p. Phosphorylated Hog1p is rapidly transported to the nucleus that results in the transcription of target genes. The HOG pathway appears to be ubiquitous in yeast. Components of HOG pathway have also been identified in Debaryomyces hansenii, a highly osmotolerant and halotolerant yeast. We have studied activation of HOG pathway in D. hansenii under different stress conditions. Our experiments demonstrated that the pathway is activated by high osmolarity, oxidative and UV stress but not by heat stress. We have provided evidence, for the first time, that D. hansenii maintains phosphorylated Dhog1p in the cytoplasm during its growth under severe osmotic stress.

Cooperative evolution in protein complexes of yeast from comparative analyses of its interaction network

A comparative analysis among Saccharomyces cerevisiae and the other four yeasts Candida glabrata, Kluyveromyces lactis, Debaryomyces hansenii, and Yarrowia lipolytica is presented. The broad evolutionary range spanned by the organisms allows to quantitatively demonstrate novel evolutionary effects in protein complexes. The evolution rates within cliques of interlinked proteins are found to bear strong multipoint correlations, witnessing a cooperative coevolution of complex subunits. The coevolution is found to be largely independent of the tendency of the subunits to have similar abundances.

Monitoring the Cell Cycle by Multi-Kinase-Dependent Regulation of Swe1/Wee1 in Budding Yeast

In eukaryotes, G(2)/M transition is induced by the activation of cyclin B-bound Cdk1, which is held in check by the protein kinase, Wee1. Recent advances in our understanding of mitotic entry in budding yeast has revealed that these cells utilize the level of Swe1 (Wee1 ortholog) phosphorylation as a means of monitoring cell cycle progression and of coordinating morphogenetic events with mitotic entry. Swe1 is phosphorylated by at least three distinct kinases at different stages of the cell cycle. This cumulative phosphorylation leads to the hyperphosphorylation and degradation of Swe1 through ubiquitin-mediated proteolysis. Thus, Swe1 functions as an important cell cycle modulator that integrates multiple upstream signals from prior cell cycle events before its ultimate degradation permits passage into mitosis.

Production of L-talitol from L-psicose by Metschnikowia koreensis LA1 isolated from soy sauce mash

A strain LA1 that can convert L-psicose to L-talitol was isolated from soy sauce mash and identified as Metschnikowia koreensis. The cells grown on L-arabitol were found to have relatively high conversion potential. Addition of D-sorbitol to the reaction mixture considerably accelerated the conversion rate of L-psicose to L-talitol. During the conversion reaction, D-sorbitol was added to the reaction mixture at 12-h intervals to maintain the concentration of D-sorbitol at 1.0%. The final conversion ratios were 81.4%, 75.2%, 73.0%, 60.4% and 43.5% using washed cells when the concentrations of L-psicose were 0.5%, 1.0%, 2.0%, 3.0% and 5.0%, respectively. The product from L-psicose was identified as L-talitol by HPLC analysis, and infrared spectroscopy, optical rotation and melting point measurements.

[The effect of succinate on respiration, transamination, and pyruvate formation in cells of the yeast Dipodascus magnusii]

The effect of succinate on the growth and respiration of the yeast Dipodascus magnusii VKM Y-1072, which is auxotrophic for thiamine and biotin, was studied. The addition of succinate to a culture grown on glucose was found to activate the respiration of cells on various substrates by enhancing the processes related to transamination reactions. In this case, aerobic fermentation (ethanol production) decreased, whereas pyruvate production increased. When succinate was added to the medium as the sole carbon source, it supported yeast growth in the absence of one of the two vitamins, thiamine or biotin, but not both. The yeast metabolism was completely respiratory, without any signs of aerobic fermentation. A drastic rise in pyruvate production in the yeast grown on glucose in the presence of succinate and the absence of biotin are also indicative of metabolic changes.

Assessment of Hansenula polymorpha and Arxula adeninivorans-derived rDNA-targeting elements for the design of Arxula adeninivorans expression vectors

Different targeting sequences derived from the Arxula adeninivorans and Hansenula polymorpha rDNA clusters were tested in A. adeninivorans integration/expression vectors. For element identification, the rDNA unit of A. adeninivorans (accession number ) was first isolated and characterized in addition to the known H. polymorpha unit. The rDNA is a cluster of some forty 7653-bp units without the 5S rDNA gene. The selected elements were integrated into a set of A. adeninivorans expression/integration vectors harbouring a TEF1 promoter - amyA ORF - PHO5 terminator sequence as reporter gene. No differences in mitotic stability, copy number and transformation frequency were observed. All transformants harboured a single copy integrated into the rDNA by a homologous recombination. In contrast, the choice of the rDNA targeting sequence was found to be of impact on productivity. Use of ETS-18S-5.8S fragments from both organisms resulted in a more than 50% increase in comparison to the use of other elements, independent of the orientation within the vector.

New yeast expression platforms based on methylotrophic Hansenula polymorpha and Pichia pastoris and on dimorphic Arxula adeninivorans and Yarrowia lipolytica - a comparison

Yeasts combine the ease of genetic manipulation and fermentation of a microbial organism with the capability to secrete and to modify proteins according to a general eukaryotic scheme. Yeasts thus provide attractive platforms for the production of recombinant proteins. Here, four important species are presented and compared: the methylotrophic Hansenula polymorpha and Pichia pastoris, distinguished by an increasingly large track record as industrial platforms, and the dimorphic species Arxula adeninivorans and Yarrrowia lipolytica, not yet established as industrial platforms, but demonstrating promising technological potential, as discussed in this article.