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Use of ars18 based vectors to increase protein production in Yarrowia lipolytica.

The isolation of ars sequence from the yeast Yarrowia lipolytica has recently been reported (Fournier et al., 1991). Vectors containing ars18 have been used to increase homologous and heterologous protein production. Examples presented are the Yarrowia lipolytica alkaline extracellular protease (AEP), the porcine alpha 1-interferon and the bovine prochymosin. A 2- to 6-fold increase in the corresponding protein production was observed and in several cases it was established that it corresponded to the copy number of plasmid in the cell.

Animals

A CRISPR-Cas9 Toolkit Enabling Tunable Integration and Transient Homologous Recombination Enhancement in Yarrowia lipolytica.

Although the oleaginous yeast Yarrowia lipolytica is a promising microbial cell factory, its application remains constrained by inefficient homology-directed repair (HDR) and a lack of precise genomic integration tools. To address these limitations, we developed a comprehensive genetic toolkit featuring three synergistic advancements. First, we systematically identified 55 neutral integration sites with tunable expression profiles, enabling stable, position-independent gene integration with predictable transcriptional output across a 12.88-fold dynamic range. Second, we established a dual-readout high-throughput screening platform combining colony morphology analysis with hrGFP fluorescence. This approach accurately measures locus-specific homologous recombination (HR) efficiency while eliminating false positives by dominant non-homologous end joining (NHEJ). Third, we engineered a transient HR enhancement system by fusing the Sae2 exonuclease to Cas9 via a flexible (GGGGS)3 linker. This fusion significantly boosts HR efficiency and surpasses the cleavage activity of unmodified Cas9 without introducing permanent genomic modifications or compromising cellular fitness. Finally, HR efficiency for single-gene integration was increased from 46.5% to 77.5% while the dual-locus editing efficiency reached 64.1% when using 500-bp homology arms, and the engineered strains demonstrated improved genetic stability compared to those with constitutive HR enhancement.

Yarrowia

Characterization of mutants of the yeast Yarrowia lipolytica defective in acetyl-coenzyme A synthetase.

The expression of the glyoxylate cycle enzymes is required for growth of the yeast Yarrowia lipolytica on acetate or fatty acids as sole carbon source. Acetyl-coenzyme A, which is produced by acetyl-coenzyme A synthetase (ACS) from acetate, is needed for induction of this expression. Acetate-non-utilizing mutants of this yeast were investigated in order to identify mutants which express no or strongly reduced activity of this enzyme. Mutations in gene ICL2 exhibited the strongest effects on the activity. In icl2 mutants, lack of ACS activity resulted in a non-induced glyoxylate cycle on acetate; however, induction on fatty acids was not affected. Gene ICL2 was identified as the structural gene encoding the monomer of ACS. It is shown that a high level of ACS activity is necessary for full expression of the glyoxylate cycle enzymes. Mutations in gene ICL1, which encodes isocitrate lyase, resulted in overproduction of ACS without any growth on acetate. A new gene (GPR1 = glyoxylate pathway regulation) was detected in which trans-dominant mutations inhibit expression of ACS and the glyoxylate cycle on acetate as carbon source.

Acetate-CoA Ligase

Complementation of Saccharomyces cerevisiae acid phosphatase mutation by a genomic sequence from the yeast Yarrowia lipolytica identifies a new phosphatase.

A Yarrowia lipolytica gene library was constructed in vector YRp7 and transformed into a Saccharomyces cerevisiae strain lacking both major acid phosphatase activities. A 2.18 kb genomic sequence restoring the ability to hydrolyze alpha-naphthyl phosphate was isolated. Its sequencing revealed an ORF encoding 358 amino acids without significant homology with any known phosphatase. A putative signal peptide and several possible sites for N-glycosylation were identified. Phosphate-regulated expression of the cloned gene was observed in Y. lipolytica. Disruption data favoured the hypothesis that it might encode a minor phosphatase species.

Acid Phosphatase

Secretion of human blood coagulation factor XIIIa by the yeast Yarrowia lipolytica.

The industrial yeast, Yarrowia lipolytica, secretes high yields of an alkaline extracellular protease (AEP), which is synthesized as a preproprotein encoded by the XPR2 gene. We investigated the possibility of using this system for the secretion of human coagulation factor XIII subunit a (FXIIIa). This protein is naturally secreted in the plasma by an unknown, signal peptide-independent mechanism and has so far been found to be nonsecretable in yeast. We have designed six hybrid genes encoding fusion proteins between increasing portions of the AEP preprodomain and the precursor or mature forms of FXIIIa. All constructs directed translocation of the FXIIIa precursor into the endoplasmic reticulum. Transport of the translocated and core-glycosylated hybrid precursor to the Golgi apparatus appeared to be strongly rate limiting, and most of the precursors appeared to be partially proteolysed. One of these constructs directed the extracellular secretion of a low amount of hyperglycosylated FXIIIa. These results indicate that fusion to the yeast AEP signal peptide and dipeptide stretch allows FXIIIa to be translocated, albeit inefficiently, through the endoplasmic reticulum and to follow a classical secretory transit.

Amino Acid Sequence

A mutant of 7SL RNA in Yarrowia lipolytica affecting the synthesis of a secreted protein.

The yeast Yarrowia lipolytica contains two genes, SCR1 and SCR2, encoding a 7SL RNA associated with a signal recognition particle (SRP). To study 7SL RNA function in vivo we have systematically substituted the two conserved nucleotides G128 and A130 in loop 1 of SCR2-encoded 7SL RNA. All single mutations in either nucleotide have no effect. All double mutations are lethal except for one which results in temperature-sensitive growth. We have studied the synthesis and secretion of an alkaline extracellular protease (AEP) in both wild-type and temperature-sensitive mutant strains. Pulse-chase labeling and immunoprecipitation of this protein show that: 1) total protein synthesis is not affected in the mutant strain; 2) levels of AEP precursors in the mutant strain are 60% less than in the wild-type strain; 3) for both strains there is no accumulation of the AEP precursors in the cytoplasm; 4) the kinetics of secretion is similar. These results suggest that mutated SRP is deficient in membrane targeting but still performs translational arrest. This is consistent with the functions of SRP observed in vitro and represents the first demonstration of such roles in vivo.

Base Sequence

A mutation in the signal recognition particle 7S RNA of the yeast Yarrowia lipolytica preferentially affects synthesis of the alkaline extracellular protease: in vivo evidence for translational arrest.

Replacement of the signal recognition particle (SRP) 7S gene (SCR1) on a replicating plasmid with scr1-1 (G to A at 129 and A to T at 131 in the consensus sequence -GNAR- in the loop of domain III) resulted in temperature sensitivity for growth of cells in which both chromosomal SRP 7S RNA genes were deleted. Pulse-chase immunoprecipitation experiments were done after a shift to non-permissive temperature using the major secreted protein the alkaline extracellular protease (AEP) as a reporter molecule. No untranslocated AEP precursor was detected in a strain with scr1-1 on a plasmid, but the amount of the largest AEP precursor (55 kD) immunoprecipitated as a percentage of total protein synthesized was reduced 68% compared to an isogenic strain with SCR1 on the plasmid. The possibility that an untranslocated precursor was synthesized but not detected because of instability was largely eliminated by detection of a 53-kD untranslocated precursor of a mutated AEP (P17M; methionine replaced proline in the second position of the pro-peptide) which chased to the 55-kD translocated AEP precursor. Thus, SRP has a role in the biosynthesis of AEP. Possibly, the scr1-1 mutation does not affect signal recognition or translational arrest but instead results in maintenance of translational arrest of AEP synthesis. The results also suggest that AEP can be translocated in vivo either co-translationally in which SRP is at least involved in biosynthesis or posttranslationally without SRP involvement.

Alleles

Growth of fermentative and non-fermentative yeasts in natural yoghurt, stored in polystyrene cartons.

Permeation of oxygen through polystyrene packaging is a factor in the growth of yeasts in natural yoghurt. Diffusion of oxygen through the packaging material can permit the growth of non-fermentative yeasts in yoghurt stored at refrigeration temperatures. Yarrowia lipolytica, a non-fermentative yeasts which does not utilize lactose was isolated from yoghurt. The growth in natural yoghurt of Yarrowia lipolytica and the lactose-fermenting yeast Kluyveromyces marxianus was investigated. Both yeasts grew in yoghurt with reduced fat content. Storage of yoghurt in an anaerobic atmosphere eliminated growth of Yarrowia lipolytica but permitted fermentative growth of Kluyveromyces marxianus.

Fermentation

Runaway evolution of telomeres in ascomycetous yeasts was accompanied by the replacement of ancestral telomeric proteins.

Telomeres are crucial parts of eukaryotic chromosomes, contributing to DNA replication, chromosome segregation, and genome stability. While in most phylogenetic lineages, telomere-maintenance systems are conserved, ascomycetous yeasts exhibit a high degree of variability in telomeric repeats and the associated proteins. The determinants that enabled this divergent evolutionary process, however, have been unclear. Here, we show that DNA-binding properties of yeast telomere-binding proteins (TBPs) support the scenario where the gradual divergence of telomeric repeats led to their replacement. We analyzed the DNA-protein interactions between Tay1p from Yarrowia lipolytica, Rap1p from Saccharomyces cerevisiae, and Taz1p from Schizosaccharomyces pombe and a set of telomeric repeats from several yeast species and delineated how the ancestral (Tay1p-like) TBPs were replaced by Rap1p (in budding yeasts) or Taz1p (in fission yeasts). We also postulate two different driving forces for these replacements: (i) Tay1p-to-Rap1p transition appears to be driven by differences in sequence preferences of Tay1p and Rap1p, while (ii) Taz1p became the principal TBP in fission yeast presumably due to its DNA-binding flexibility. Together, our results suggest that in telomeric DNA-protein complexes, the replacement of protein component triggered by the initial variation in DNA sequence space opens the door to further divergence in a runaway-style evolution.

Telomere-Binding Proteins

Multi-Omic Insights Into Mediterranean Diet-Associated Microbiota.

This study aimed to evaluate the gut microbiota and mycobiota composition, depending on the Mediterranean diet (MD) adherence, using metataxonomics. Combining metagenomics and metatranscriptomics, we also investigate the gene expression level in the bacterial community. Two groups of healthy subjects greatly differing in adherence were selected. Significant differences in microbiota composition were observed between individuals with high adherence (HAMD; mean 10.5 +/- 0.9 points) and low adherence (LAMD; 5.23 +/- 83 points). Notably, the olive oil, vegetable, and fruit consumption presented an important discriminant power between groups. Saccharomyces, Penicillium, and Candida were the most abundant genera. Mycobiota richness was higher in LAMD than in HAMD. Aspergillus was identified as a biomarker for LAMD, whereas Yarrowia, a potential probiotic, was a biomarker for HAMD. Metatranscriptomics indicated that Bacillota was the most metabolically active phylum in the gut microbiota. The low-abundant genus, Methanobrevibacter, showed high transcriptional activity, contributing to the crucial methanogenesis process. Gene expression analyses further highlighted functional differences. Overall, HAMD microbiota presented increased metabolic activity, protein synthesis, and cellular mobility. Overexpression of flagellin and urease genes may enhance immune response in HAMD. Further metatranscriptomic studies are necessary to deepen our understanding of intestinal microbiota transcriptional programs and their interactions with the diet and human health.

Humans

Antibodies directed against a yeast carboxyl-terminal peroxisomal targeting signal specifically recognize peroxisomal proteins from various yeasts.

The carboxyl-terminal tripeptide Ala-Lys-Ile is essential for targeting Candida tropicalis trifunctional enzyme (hydratase-dehydrogenase-epimerase) to peroxisomes of both Candida albicans and Saccharomyces cerevisiae (Aitchison,J.D., Murray, W.W. and Rachubinski, R. A. (1991).J. Biol. Chem. 266, 23197-23203). We investigated the possibility that this tripeptide may act as a general peroxisomal targeting signal (PTS) for other proteins in the yeasts C. tropicalis, C. albicans, Yarrowia lipolytica and S. cerevisiae, and in rat liver. Anti-AKI antibodies raised against the carboxyl-terminal 12 amino acids of trifunctional enzyme were used to search for this PTS in proteins of these yeasts and of rat liver. The anti-AKI antibodies reacted exclusively with multiple peroxisomal proteins from the yeasts C. tropicalis, C. albicans and Y. lipolytica. There was a weak reaction of the antibodies with one peroxisomal protein from S. cerevisiae and no reaction with peroxisomal proteins from rat liver. Antibodies directed against a synthetic peptide containing a carboxyl-terminal Ser-Lys-Leu PTS (Gould, S. J., Krisans, S., Keller, G.-A. and Subramani, S. (1990). J. Cell Biol. 110,27-34) reacted with multiple peroxisomal proteins of rat liver and with peroxisomal proteins of yeast distinct from those identified with anti-AKI antibodies. These results provide evidence that several peroxisomal proteins of different yeasts contain a PTS antigenically similar to that of C. tropicalis trifunctional enzyme and that this signal is absent from peroxisomal proteins from at least one mammalian system, rat liver.

Amino Acid Sequence

A chromosome-level genome assembly of Lycoris radiata reveals the evolutionary origin of Amaryllidaceae alkaloids and elucidates the complete galanthamine biosynthetic pathway.

Amaryllidaceae alkaloids (AmAs) comprise a structurally diverse group of specialized metabolites produced almost exclusively by species of the Amaryllidoideae subfamily and are of substantial pharmacological importance. However, the limited availability of high-quality genomes from Amaryllidoideae plants has constrained systematic investigations of the genes and evolutionary processes underlying AmA biosynthesis. Here, we present a chromosome-level genome assembly of Lycoris radiata, which enabled the discovery of key downstream enzymes in the galanthamine biosynthetic pathway and uncovered reversible reactions between two critical metabolite pairs. These findings provide new mechanistic insight into pathway architecture and enable reconstruction of the galanthamine biosynthetic pathway in Yarrowia lipolytica. Comparative genomic analyses indicate that several core genes for AmA biosynthesis originated in ancestral angiosperms, whereas the complete pathway was likely assembled in the Amaryllidoideae subfamily through gene duplication and neofunctionalization. Furthermore, integrated metabolomic and transcriptomic analyses suggest that roots contribute actively to AmA metabolism in Lycoris. Together, these findings provide a genomic and biochemical framework for understanding the evolution and engineering of AmA biosynthesis.

Lycoris

Yeast systems for the commercial production of heterologous proteins.

Yeasts are attractive hosts for the production of heterologous proteins. Unlike prokaryotic systems, their eukaryotic subcellular organization enables them to carry out many of the post-translational folding, processing and modification events required to produce "authentic" and bioactive mammalian proteins. In addition, they retain the advantages of a unicellular microorganism, with respect to rapid growth and ease of genetic manipulation. The vast majority of yeast expression work has focused on the well-characterized baker's yeast Saccharomyces cerevisiae. However, with the development of DNA transformation technologies, a growing number of non-Saccharomyces yeasts are becoming available as hosts for recombinant polypeptide production. These include Hansenula polymorpha, Kluyveromyces lactis, Pichia pastoris, Schizosaccharomyces pombe, Schwanniomyces occidentalis and Yarrowia lipolytica. The performance of these alternative yeast expression systems is reviewed here relative to S. cerevisiae, and the advantages and limitations of these systems are discussed.

Animals

An update on clinically relevant, rare, and emerging Candida and Saccharomycotina yeasts that have been recently reclassified from Candida.

SUMMARYMany yeast species causing life-threatening invasive infections that were formerly classified in the genus Candida have been reclassified due to their evolutionary and phylogenetic relationships elucidated by DNA sequencing methods that are increasingly using whole genomes. This review explores the evolving taxonomy, epidemiology, and clinical implications of clinically relevant, rare, emerging Candida and Saccharomycotina yeasts that have recently been reclassified from Candida. This article highlights the urgent need for intensified research efforts to enhance knowledge and improve outcomes in the management of infections caused by these yeasts. Communicating results from molecular phylogenetic studies of yeasts, which lead to their reclassification, is of great importance to the medical mycology community to implement such results in clinical practice.

Humans