Use of MET3 promoters for regulated gene expression in Ashbya gossypii

New Promoters for Metabolic Engineering of Ashbya gossypii

Ashbya gossypii is a filamentous fungus that is currently exploited for the industrial production of riboflavin. In addition, metabolically engineered strains of A. gossypii have also been described as valuable biocatalysts for the production of different metabolites such as folic acid, nucleosides, and biolipids. Hence, bioproduction in A. gossypii relies on the availability of well-performing gene expression systems both for endogenous and heterologous genes. In this regard, the identification of novel promoters, which are critical elements for gene expression, decisively helps to expand the A. gossypii molecular toolbox. In this work, we present an adaptation of the Dual Luciferase Reporter (DLR) Assay for promoter analysis in A. gossypii using integrative cassettes. We demonstrate the efficiency of the analysis through the identification of 10 new promoters with different features, including carbon source-regulatable abilities, that will highly improve the gene expression platforms used in A. gossypii. Three novel strong promoters (P_CCW12, P_SED1, and P_TSA1) and seven medium/weak promoters (P_HSP26, P_AGL366C, P_TMA10, P_CWP1, P_AFR038W, P_PFS1, and P_CDA2) are presented. The functionality of the promoters was further evaluated both for the overexpression and for the underexpression of the A. gossypii MSN2 gene, which induced significant changes in the sporulation ability of the mutant strains.

Sporulation in Ashbya gossypii

Ashbya gossypii is a filamentous ascomycete belonging to the yeast family of Saccharomycetaceae. At the end of its growth phase Ashbya generates abundant amounts of riboflavin and spores that form within sporangia derived from fragmented cellular compartments of hyphae. The length of spores differs within species of the genus. Needle-shaped Ashbya spores aggregate via terminal filaments. A. gossypii is a homothallic fungus which may possess a and α mating types. However, the solo-MATa type strain is self-fertile and sporulates abundantly apparently without the need of prior mating. The central components required for the regulation of sporulation, encoded by IME1, IME2, IME4, KAR4, are conserved with Saccharomyces cerevisiae. Nutrient depletion generates a strong positive signal for sporulation via the cAMP-PKA pathway and SOK2, which is also essential for sporulation. Strong inhibitors of sporulation besides mutations in the central regulatory genes are the addition of exogenous cAMP or the overexpression of the mating type gene MATα2. Sporulation has been dissected using gene-function analyses and global RNA-seq transcriptomics. This revealed a role of Msn2/4, another potential PKA-target, for spore wall formation and a key dual role of the protein A kinase Tpk2 at the onset of sporulation as well as for breaking the dormancy of spores to initiate germination. Recent work has provided an overview of ascus development, regulation of sporulation and spore maturation. This will be summarized in the current review with a focus on the central regulatory genes. Current research and open questions will also be discussed.

Overexpression of RAD51 Enables PCR-Based Gene Targeting in Lager Yeast

Lager beer fermentations rely on specific polyploid hybrids between Saccharomyces cerevisiae and Saccharomyces eubayanus falling into the two groups of S. carlsbergensis/Saaz-type and S. pastorianus/Frohberg-type. These strains provide a terroir to lager beer as they have long traditional associations and local selection histories with specific breweries. Lager yeasts share, based on their common origin, several phenotypes. One of them is low transformability, hampering the gene function analyses required for proof-of-concept strain improvements. PCR-based gene targeting is a standard tool for manipulating S. cerevisiae and other ascomycetes. However, low transformability paired with the low efficiency of homologous recombination practically disable targeted gene function analyses in lager yeast strains. For genetic manipulations in lager yeasts, we employed a yeast transformation protocol based on lithium-acetate/PEG incubation combined with electroporation. We first introduced freely replicating CEN/ARS plasmids carrying ScRAD51 driven by a strong heterologous promoter into lager yeast. RAD51 overexpression in the Weihenstephan 34/70 lager yeast was necessary and sufficient in our hands for gene targeting using short-flanking homology regions of 50 bp added to a selection marker by PCR. We successfully targeted two independent loci, ScADE2/YOR128C and ScHSP104/YLL026W, and confirmed correct integration by diagnostic PCR. With these modifications, genetic alterations of lager yeasts can be achieved efficiently and the RAD51-containing episomal plasmid can be removed after successful strain construction.

Toxicity of Potential Fungal Defense Proteins towards the Fungivorous Nematodes Aphelenchus avenae and Bursaphelenchus okinawaensis

Our results support the hypothesis that cytoplasmic proteins abundant in fungal fruiting bodies are involved in fungal resistance against predation. The toxicity of these proteins toward stylet-feeding nematodes, which are also capable of feeding on plants, and the abundance of these proteins in edible mushrooms, may open possible avenues for biological crop protection against parasitic nematodes, e.g., by expression of these proteins in crops.

Resistance of fungi to predation is thought to be mediated by toxic metabolites and proteins. Many of these fungal defense effectors are highly abundant in the fruiting body and not produced in the vegetative mycelium. The defense function of fruiting body-specific proteins, however, including cytoplasmically localized lectins and antinutritional proteins such as biotin-binding proteins, is mainly based on toxicity assays using bacteria as a heterologous expression system, with bacterivorous/omnivorous model organisms as predators. Here, we present an ecologically more relevant experimental setup to assess the toxicity of potential fungal defense proteins towards the fungivorous, stylet-feeding nematodes Aphelenchus avenae and Bursaphelenchus okinawaensis. As a heterologous expression host, we exploited the filamentous fungus Ashbya gossypii. Using this new system, we assessed the toxicity of six previously characterized, cytoplasmically localized, potential defense proteins from fruiting bodies of different fungal phyla against the two fungivorous nematodes. We found that all of the tested proteins were toxic against both nematodes, albeit to various degrees. The toxicity of these proteins against both fungivorous and bacterivorous nematodes suggests that their targets have been conserved between the different feeding groups of nematodes and that bacterivorous nematodes are valid model organisms to assess the nematotoxicity of potential fungal defense proteins.

IMPORTANCE Our results support the hypothesis that cytoplasmic proteins abundant in fungal fruiting bodies are involved in fungal resistance against predation. The toxicity of these proteins toward stylet-feeding nematodes, which are also capable of feeding on plants, and the abundance of these proteins in edible mushrooms, may open possible avenues for biological crop protection against parasitic nematodes, e.g., by expression of these proteins in crops.

The Promoter Toolbox for Recombinant Gene Expression in Trichoderma reesei

The ascomycete Trichoderma reesei is one of the main fungal producers of cellulases and xylanases based on its high production capacity. Its enzymes are applied in food, feed, and textile industry or in lignocellulose hydrolysis in biofuel and biorefinery industry. Over the last years, the demand to expand the molecular toolbox for T. reesei to facilitate genetic engineering and improve the production of heterologous proteins grew. An important instrument to modify the expression of key genes are promoters to initiate and control their transcription. To date, the most commonly used promoter for T. reesei is the strong inducible promoter of the main cellobiohydrolase cel7a. Beside this one, there is a number of alternative inducible promoters derived from other cellulase- and xylanase encoding genes and a few constitutive promoters. With the advances in genomics and transcriptomics the identification of new constitutive and tunable promoters with different expression strength was simplified. In this review, we will discuss new developments in the field of promoters and compare their advantages and disadvantages. Synthetic expression systems constitute a new option to control gene expression and build up complex gene circuits. Therefore, we will address common structural features of promoters and describe options for promoter engineering and synthetic design of promoters. The availability of well-characterized gene expression control tools is essential for the analysis of gene function, detection of bottlenecks in gene networks and yield increase for biotechnology applications.

The APSES protein Sok2 is a positive regulator of sporulation in Ashbya gossypii

Ashbya gossypii is a homothallic, flavinogenic, filamentous ascomycete that starts overproduction of riboflavin and fragments its mycelium quantitatively into spore producing sporangia at the end of a growth phase. Mating is not required for sporulation and the standard homothallic laboratory strain is a MATa strain. Here we show that ectopic expression of Saccharomyces cerevisiae MATα2 in A. gossypii completely suppresses sporulation, inhibits riboflavin overproduction and downregulates among others AgSOK2. AgSok2 belongs to a fungal-specific group of (APSES) transcription factors. Deletion of AgSOK2 strongly reduces riboflavin production and blocks sporulation. The initiator of meiosis, AgIME1, is a transcription factor essential for sporulation. We characterized the AgIME1 promoter region required for complementation of the Agime1 mutant. Reporter assays with AgIME1 promoter fragments fused to lacZ showed that AgSok2 does not control AgIME1 transcription. However, global transcriptome analysis identified two other essential regulators of sporulation, AgIME2 and AgNDT80, as potential targets of AgSok2. Our data suggest that sporulation and riboflavin production in A. gossypii are under mating type locus and nutritional control. Sok2, a target of the cAMP/protein kinase A pathway, serves as a central positive regulator to promote sporulation. This contrasts Saccharomyces cerevisiae where Sok2 is a repressor of IME1 transcription.

L-Methionine repressible promoters for tuneable gene expression in Trichoderma reesei

BACKGROUND

Trichoderma reesei is the main producer of lignocellulolytic enzymes that are required for plant biomass hydrolysis in the biorefinery industry. Although the molecular toolbox for T. reesei is already well developed, repressible promoters for strain engineering and functional genomics studies are still lacking. One such promoter that is widely employed for yeasts is that of the L-methionine repressible MET3 gene, encoding ATP sulphurylase.

RESULTS

We show that the MET3 system can only be applied for T. reesei when the cellulase inducing carbon source lactose is used but not when wheat straw, a relevant lignocellulosic substrate for enzyme production, is employed. We therefore performed a transcriptomic screen for genes that are L-methionine repressible in a wheat straw culture. This analysis retrieved 50 differentially regulated genes of which 33 were downregulated. Among these, genes encoding transport proteins as well as iron containing DszA like monooxygenases and TauD like dioxygenases were strongly overrepresented. We show that the promoter region of one of these dioxygenases can be used for the strongly repressible expression of the Aspergillus niger sucA encoded extracellular invertase in T. reesei wheat straw cultures. This system is also portable to other carbon sources including D-glucose and glycerol as demonstrated by the repressible expression of the Escherichia coli lacZ encoded ß-galactosidase in T. reesei.

CONCLUSION

We describe a novel, versatile set of promoters for T. reesei that can be used to drive recombinant gene expression in wheat straw cultures at different expression strengths and in an L-methionine repressible manner. The dioxygenase promoter that we studied in detail is furthermore compatible with different carbon sources and therefore applicable for manipulating protein production as well as functional genomics with T. reesei.

Use of the cysteine-repressible HpMET3 promoter as a novel tool to regulate gene expression in Hansenula polymorpha

OBJECTIVES

The promoter of HpMET3, encoding an ATP sulfurylase, was evaluated for its potential as a repressible promoter to downregulate the expression of target genes in the thermotolerant, methylotrophic yeast Hansenula polymorpha.

RESULTS

The expression of lacZ under the control of the 0.6 kb HpMET3 promoter was efficiently downregulated by cysteine, but not by methionine or sulfate. The HpMET3 promoter was used to generate a conditional mutant of the HpPMT2 gene encoding an O-mannosyltransferase, which is involved in post-translational protein modification. The addition of 0.5 mM cysteine adversely affected the growth of the conditional HpMET3(p)-Hppmt2 mutant strain by downregulating transcription of HpPMT2 to approx. 40 % of the normal levels, indicating that the HpPMT2 gene is essential for cell viability. However, the HpMET3 promoter was neither induced nor repressed in the heterologous host Saccharomyces cerevisiae.

CONCLUSION

Our results reveal that the cysteine-repressible HpMET3 promoter is a useful tool that downregulates the expression of various genes in H. polymorpha.

Increased production of inosine and guanosine by means of metabolic engineering of the purine pathway in Ashbya gossypii

Background

Inosine and guanosine monophosphate nucleotides are convenient sources of the umami flavor, with attributed beneficial health effects that have renewed commercial interest in nucleotide fermentations. Accordingly, several bacterial strains that excrete high levels of inosine and guanosine nucleosides are currently used in the food industry for this purpose.

Results

In the present study, we show that the filamentous fungus Ashbya gossypii, a natural riboflavin overproducer, excretes high amounts of inosine and guanosine nucleosides to the culture medium. Following a rational metabolic engineering approach of the de novo purine nucleotide biosynthetic pathway, we increased the excreted levels of inosine up to 27-fold.

Conclusions

We generated Ashbya gossypii strains with improved production titers of inosine and guanosine. Our results point to Ashbya gossypii as the first eukaryotic microorganism representing a promising candidate, susceptible to further manipulation, for industrial nucleoside fermentation.

Electronic supplementary material

The online version of this article (doi:10.1186/s12934-015-0234-4) contains supplementary material, which is available to authorized users.

Combination of ERG9 Repression and Enzyme Fusion Technology for Improved Production of Amorphadiene in Saccharomyces cerevisiae

The yeast strain (Saccharomyces cerevisiae) MTCC 3157 was selected for combinatorial biosynthesis of plant sesquiterpene amorpha-4,11-diene. Our main objective was to overproduce amorpha 4-11-diene, which is a key precursor molecule of artemisinin (antimalarial drug) produced naturally in plant Artemisia annua through mevalonate pathway. Farnesyl diphosphate (FPP) is a common intermediate metabolite of a variety of compounds in the mevalonate pathway of yeast and leads to the production of ergosterols, dolichol and ubiquinone, and so forth. In our studies, FPP converted to amorphadiene (AD) by expressing heterologous amorphadiene synthase (ADS) in yeast. First, ERG9 (squalane synthase) promoter of yeast was replaced with repressible methionine (MET3) promoter by using bipartite gene fusion method. Further to overcome the loss of the intermediate FPP through competitive pathways in yeast, fusion protein technology was adopted and farnesyldiphosphate synthase (FPPS) of yeast has been coupled with amorphadiene synthase (ADS) of plant origin (Artemisia annua L.) where amorphadiene production was improved by 2-fold (11.2 mg/L) and 4-fold (25.02 mg/L) in yeast strains YCF-002 and YCF-005 compared with control strain YCF-AD (5.5 mg/L), respectively.

Subcellular localization of the fatty acyl reductase involved in pheromone biosynthesis in the tobacco budworm, Heliothis virescens (Noctuidae: Lepidoptera)

Sex pheromone components are produced in specialized glands of female moths via well-characterized biosynthetic pathways, where a Fatty Acyl Reductase (FAR) is often essential for producing the specific ratio of the different pheromone components. The subcellular localization and membrane topology of FARs is important for understanding how pheromones are synthesized and exported to the exterior for release. We investigated the subcellular localization of HvFAR from the noctuid moth Heliothis virescens by producing recombinant fusion proteins with green fluorescent protein (GFP) in yeast. A C-terminally tagged construct was localized to the endoplasmic reticulum (ER) and retained full reductive activity on a broad range of saturated and unsaturated fatty acyl precursors. In contrast, an N-terminally-tagged construct was poorly expressed in the cytoplasm and was not enzymatically active, indicating that HvFAR requires a free N-terminal for both proper targeting and catalytic activity. A series of truncations of the N-and C-termini of HvFAR was conducted based on in silico-predicted hydrophobic domains and transmembrane regions. The N-terminally truncated protein was found in the cytoplasm and did not retain activity, emphasizing the importance of the N-terminal for FAR function. In addition, the orientation in the membrane of the C-terminus-tagged HvFAR-GFP construct was analyzed using a fluorescence protease protection (FPP) assay, implying that the C-terminal of HvFAR is orientated towards the cytoplasm. These results, together with previous data on the localization of desaturases, confirm the importance of the ER as a subcellular site of pheromone production.

Repressible promoters - a novel tool to generate conditional mutants in Pichia pastoris

BACKGROUND

Repressible promoters are a useful tool for down-regulating the expression of genes, especially those that affect cell viability, in order to study cell physiology. They are also popular in biotechnological processes, like heterologous protein production.

RESULTS

Here we present five novel repressible Pichia pastoris promoters of different strength: PSER1, PMET3, PTHR1, PPIS1 and PTHI11. eGFP was expressed under the control of each of these promoters and its fluorescence could be successfully decreased in liquid culture by adding different supplements. We also expressed the essential genes with different native promoter strength, ERO1 and PDI1, under the control of two of the novel promoters. In our experiments, a clear down-regulation of both repressible promoters on transcriptional level could be achieved. Compared to the transcript levels of these two genes when expressed under the control of their native promoters, only ERO1 was significantly down-regulated.

CONCLUSION

Our results show that all of the novel promoters can be used for repression of genes in liquid culture. We also came to the conclusion that the choice of the repressible promoter is of particular importance. For a successful repression experiment it is crucial that the native promoter of a gene and the repressible promoter in its non-repressed state are of similar strength.

Yap1-dependent oxidative stress response provides a link to riboflavin production in Ashbya gossypii

Ashbya gossypii is a natural overproducer of riboflavin. Overproduction of riboflavin can be induced by environmental stress, e.g. nutritional or oxidative stress. The Yap-protein family has a well-documented role in stress response. Particularly, Yap1 has a major role in directing the oxidative stress responses. The A. gossypii YAP-family consists of only three genes in contrast to its closest relative Eremothecium cymbalariae, which has four YAP-homologs. Gene order at Eremothecium YAP-loci is conserved with the reconstructed yeast ancestor. AgYap1p is unique amongst Yap-homologs as it lacks the cysteine-rich domains (CRDs). AgYAP1 expression is inducible and GFP-AgYap1 localizes to the nucleus. Agyap1 mutants displayed higher sensitivity against oxidative stress - H(2)O(2) and menadione - and are strongly reduced in riboflavin production. High levels of cAMP, which also reduce riboflavin production, show a synergistic effect on this sensitivity. AgYAP1 and a chimera of AgYAP1 (with the DNA-binding domain) and ScYAP1 (with the CRDs) can both complement the Scyap1 oxidative stress sensitivity. This suggests that the DNA-binding sites of ScYap1 are conserved in A. gossypii. Expression of AgRIB4, which contains three putative Yap1-binding sites, assayed via a lacZ-reporter gene was strongly reduced in an Agyap1 mutant suggesting a direct involvement of AgYap1 in riboflavin production. Furthermore, our data show that application of H(2)O(2) stress leads to an increase in riboflavin production in a Yap1-dependent manner.

A lectin-mediated resistance of higher fungi against predators and parasites

Fruiting body lectins are ubiquitous in higher fungi and characterized by being synthesized in the cytoplasm and up-regulated during sexual development. The function of these lectins is unclear. A lack of phenotype in sexual development upon inactivation of the respective genes argues against a function in this process. We tested a series of characterized fruiting body lectins from different fungi for toxicity towards the nematode Caenorhabditis elegans, the mosquito Aedes aegypti and the amoeba Acanthamoeba castellanii. Most of the fungal lectins were found to be toxic towards at least one of the three target organisms. By altering either the fungal lectin or the glycans of the target organisms, or by including soluble carbohydrate ligands as competitors, we demonstrate that the observed toxicity is dependent on the interaction between the fungal lectins and specific glycans in the target organisms. The toxicity was found to be dose-dependent such that low levels of lectin were no longer toxic but still led to food avoidance by C. elegans. Finally, we show, in an ecologically more relevant scenario, that challenging the vegetative mycelium of Coprinopsis cinerea with the fungal-feeding nematode Aphelenchus avenae induces the expression of the nematotoxic fruiting body lectins CGL1 and CGL2. Based on these findings, we propose that filamentous fungi possess an inducible resistance against predators and parasites mediated by lectins that are specific for glycans of these antagonists.

A Bnr-like formin links actin to the spindle pole body during sporulation in the filamentous fungus Ashbya gossypii

Formin proteins are nucleators of actin filaments and regulators of the microtubule cytoskeleton. As such, they play important roles in the development of yeast and other fungi. We show here that AgBnr2, a homologue of the ScBnr1 formin from the filamentous fungus Ashbya gossypii, localizes to the spindle pole body (SPB), the fungal analogue of the centrosome of metazoans. This protein plays an important role in the development of the typical needle-shaped spores of A. gossypii, as suggested by several findings. First, downregulation of AgBNR2 causes defects in sporangium formation and a decrease in the total spore number. Second, a fusion of AgBNR2 to GFP that is driven by the native AgBNR2 promoter is only visible in sporangia. Third, AgBnr2 interacts with a AgSpo21, a sporulation-specific component of the SPB. Furthermore, we provide evidence that AgBnr2 might nucleate actin cables, which are connected to SPBs during sporulation. Our findings add to our understanding of fungal sporulation, particularly the formation of spores with a complex, elongated morphology, and provide novel insights into formin function.

Analysis of flocculins in Ashbya gossypii reveals FIG2 regulation by TEC1

For 95% of the Ashbya gossypii protein-encoding genes there is a Saccharomyces cerevisiae homolog. Out of these 90% are arranged in a conserved, syntenic, gene order. Interestingly, A. gossypii adhesins, encoded by homologs of S. cerevisiae FLO-genes, are found in non-syntenic positions. A. gossypii contains only a small set of adhesins: two FLO5, a FLO11 and a FIG2 homolog, but no FLO1, FLO9, or FLO10 homolog. Here we present the functional analysis of the A. gossypii adhesins and their potential transcriptional regulators SFL1, FLO8, and TEC1. Deletion of individual classes of FLO-genes did not reveal any phenotype. Lack of SFL1 or FLO8 showed reduced growth. The expression of adhesins in different strain backgrounds was tested using promoter-lacZ-fusions. We found that SFL1 acts as a suppressor of one of the FLO5 genes and FLO8 but particularly of FIG2. Interestingly, FIG2 expression was abolished in a tec1 mutant. We identified three potential Tec1-binding sites in the FIG2-promoter by similarity to S. cerevisiae Tec1-binding sites. The AgCHT2 promoter, which regulates a sporulation specific chitinase, also harbours potential Tec1-binding sites. Consequently, expression of CHT2 was not detected in a tec1 strain. This suggests that Tec1- binding sites are conserved between A. gossypii and S. cerevisiae even though there are different Tec1 target genes in each of these organisms.

N-acetylglucosamine utilization by Saccharomyces cerevisiae based on expression of Candida albicans NAG genes

Synthesis of chitin de novo from glucose involves a linear pathway in Saccharomyces cerevisiae. Several of the pathway genes, including GNA1, are essential. Genes for chitin catabolism are absent in S. cerevisiae. Therefore, S. cerevisiae cannot use chitin as a carbon source. Chitin is the second most abundant polysaccharide after cellulose and consists of N-acetylglucosamine (GlcNAc) moieties. Here, we have generated S. cerevisiae strains that are able to use GlcNAc as a carbon source by expressing four Candida albicans genes (NAG3 or its NAG4 paralog, NAG5, NAG2, and NAG1) encoding a GlcNAc permease, a GlcNAc kinase, a GlcNAc-6-phosphate deacetylase, and a glucosamine-6-phosphate deaminase, respectively. Expression of NAG3 and NAG5 or NAG4 and NAG5 in S. cerevisiae resulted in strains in which the otherwise-essential ScGNA1 could be deleted. These strains required the presence of GlcNAc in the medium, indicating that uptake of GlcNAc and its phosphorylation were achieved. Expression of all four NAG genes produced strains that could use GlcNAc as the sole carbon source for growth. Utilization of a GlcNAc catabolic pathway for bioethanol production using these strains was tested. However, fermentation was slow and yielded only minor amounts of ethanol (approximately 3.0 g/liter), suggesting that fructose-6-phosphate produced from GlcNAc under these conditions is largely consumed to maintain cellular functions and promote growth. Our results present the first step toward tapping a novel, renewable carbon source for biofuel production.

A plasmid collection for PCR-based gene targeting in the filamentous ascomycete Ashbya gossypii

PCR-based gene targeting with heterologous markers is an efficient method to delete genes, generate gene fusions, and modulate gene expression. For the yeasts Saccharomyces cerevisiae and Schizosaccharomyces pombe, several plasmid collections are available covering a wide range of tags and markers. For several reasons, many of these cassettes cannot be used in the filamentous ascomycete Ashbya gossypii. This article describes the construction of 93 heterologous modules for C- and N-terminal tagging and promoter replacements in A. gossypii. The performance of 12 different fluorescent tags was evaluated by monitoring their brightness, detectability, and photostability when fused to the myosin light-chain protein Mlc2. Furthermore, the thiamine-repressible S. cerevisiae THI13 promoter was established to regulate gene expression in A. gossypii. This collection will help accelerate analysis of gene function in A. gossypii and in other ascomycetes where S. cerevisiae promoter elements are functional.

A molecular toolbox for manipulating Eremothecium coryli

The genus Eremothecium contains dimorphic and filamentous fungal species, most notably Eremothecium sinecaudum (Holleya sinecauda), a dimorphic plant pathogen, which was isolated from mustard seeds, and Eremothecium gossypii (Ashbya gossypii), a filamentous fungus, which is well known for its ability to produce riboflavin. In this study, we present the initial molecular characterization of another Eremothecium species classified as Eremothecium coryli. E.coryli is a dimorphic fungus. We have developed, based on previously described reagents, a transformation system for E. coryli using kanMX and NATMX3 as dominant selectable marker genes on freely replicating plasmids conferring resistance to the antibiotics G418 and nourseothricin, respectively. As reporter genes we could introduce lacZ and GFP, which were controlled either by the AgTEF1 promoter or by regulatable MET promoters derived from the A. gossypii and Saccharomyces cerevisiae MET3 genes. These newly established tools will allow a detailed comparison of different growth modes in filamentous or dimorphic species within the genus Eremothecium.