Genome Sequence of the Oleaginous Yeast Yarrowia lipolytica H222

Insights into the Genomic and Phenotypic Landscape of the Oleaginous Yeast Yarrowia lipolytica

Although Yarrowia lipolytica is a model yeast for the study of lipid metabolism, its diversity is poorly known, as studies generally consider only a few standard laboratory strains. To extend our knowledge of this biotechnological workhorse, we investigated the genomic and phenotypic diversity of 56 natural isolates. Y. lipolytica is classified into five clades with no correlation between clade membership and geographic or ecological origin. A low genetic diversity (π = 0.0017) and a pan-genome (6528 genes) barely different from the core genome (6315 genes) suggest Y. lipolytica is a recently evolving species. Large segmental duplications were detected, totaling 892 genes. With three new LTR-retrotransposons of the Gypsy family (Tyl4, Tyl9, and Tyl10), the transposable element content of genomes appeared diversified but still low (from 0.36% to 3.62%). We quantified 34 traits with substantial phenotypic diversity, but genome-wide association studies failed to evidence any associations. Instead, we investigated known genes and found four mutational events leading to XPR2 protease inactivation. Regarding lipid metabolism, most high-impact mutations were found in family-belonging genes, such as ALK or LIP, and therefore had a low phenotypic impact, suggesting that the huge diversity of lipid synthesis and accumulation is multifactorial or due to complex regulations.

Establishment of a near-contiguous genome sequence of the citric acid producing yeast Yarrowia lipolytica DSM 3286 with resolution of rDNA clusters and telomeres

Yarrowia lipolytica is an oleaginous yeast that is particularly suitable for the sustainable production of secondary metabolites. The genome of this yeast is characterized by its relatively large size and its high number of different rDNA clusters located in its telomeric regions. However, due to the presence of long repetitive elements in the sub-telomeric regions, rDNA clusters and telomeres are missing in current genome assemblies of Y. lipolytica. Here, we present the near-contiguous genome sequence of the biotechnologically relevant strain DSM 3286. We employed a hybrid assembly strategy combining Illumina and nanopore sequencing reads to integrate all six rDNA clusters as well as telomeric repeats into the genome sequence. By fine-tuning of DNA isolation and library preparation protocols, we were able to create ultra-long reads that not only contained multiples of mitochondrial genomes but also shed light on the inter- and intra-chromosomal diversity of rDNA cluster types. We show that there are ten different rDNA units present in this strain that additionally appear in a predefined order in a cluster. Based on single reads, we also demonstrate that the number of rDNA repeats in a specific cluster varies from cell to cell within a population.

Yarrowia lipolytica Strains and Their Biotechnological Applications: How Natural Biodiversity and Metabolic Engineering Could Contribute to Cell Factories Improvement

Among non-conventional yeasts of industrial interest, the dimorphic oleaginous yeast Yarrowia lipolytica appears as one of the most attractive for a large range of white biotechnology applications, from heterologous proteins secretion to cell factories process development. The past, present and potential applications of wild-type, traditionally improved or genetically modified Yarrowia lipolytica strains will be resumed, together with the wide array of molecular tools now available to genetically engineer and metabolically remodel this yeast. The present review will also provide a detailed description of Yarrowia lipolytica strains and highlight the natural biodiversity of this yeast, a subject little touched upon in most previous reviews. This work intends to fill this gap by retracing the genealogy of the main Yarrowia lipolytica strains of industrial interest, by illustrating the search for new genetic backgrounds and by providing data about the main publicly available strains in yeast collections worldwide. At last, it will focus on exemplifying how advances in engineering tools can leverage a better biotechnological exploitation of the natural biodiversity of Yarrowia lipolytica and of other yeasts from the Yarrowia clade.

Synthetic biology, systems biology, and metabolic engineering of Yarrowia lipolytica toward a sustainable biorefinery platform

Yarrowia lipolytica is an oleaginous yeast that has been substantially engineered for production of oleochemicals and drop-in transportation fuels. The unique acetyl-CoA/malonyl-CoA supply mode along with the versatile carbon-utilization pathways makes this yeast a superior host to upgrade low-value carbons into high-value secondary metabolites and fatty acid-based chemicals. The expanded synthetic biology toolkits enabled us to explore a large portfolio of specialized metabolism beyond fatty acids and lipid-based chemicals. In this review, we will summarize the recent advances in genetic, omics, and computational tool development that enables us to streamline the genetic or genomic modification for Y. lipolytica. We will also summarize various metabolic engineering strategies to harness the endogenous acetyl-CoA/malonyl-CoA/HMG-CoA pathway for production of complex oleochemicals, polyols, terpenes, polyketides, and commodity chemicals. We envision that Y. lipolytica will be an excellent microbial chassis to expand nature's biosynthetic capacity to produce plant secondary metabolites, industrially relevant oleochemicals, agrochemicals, commodity, and specialty chemicals and empower us to build a sustainable biorefinery platform that contributes to the prosperity of a bio-based economy in the future.

Yarrowia lipolytica causes sporadic cases and local outbreaks of infections and colonisation

BACKGROUND

Yarrowia lipolytica belongs to the normal human microbiota but is also found in substrates with high contents in lipids and used in biotechnological processes. It is sometimes reported as human pathogen and especially in catheter-related candidaemia.

OBJECTIVES

Two apparently grouped cases of infections and/or contamination were reported involving 3 and 9 patients, respectively, in two hospitals. The goal of this study was to design a molecular tool to study the genetic diversity of Y lipolytica and confirm or not the common source of contamination during these grouped cases.

METHODS

Given that there is no genotyping method, we used genomic markers assessed on environmental isolates to determine intra-species relationship. We selected five highly polymorphic intergenic regions, totalling more than 3200 bp and sequenced them for clinical (n = 20) and environmental (n = 14) isolates. Antifungal susceptibility was determined by EUCAST broth microdilution method.

RESULTS

Multiple alignment of the five sequences revealed divergence of 0%-5.8% between isolates as compared to approximately 0.2%-0.25% after alignment of whole genomes, suggesting their potential usefulness to establish genetic relatedness. The analysis showed the multiple origins of the isolates. It uncovered two grouped case of fungaemia involving 3 and 2 patients, respectively. It also revealed several unrelated sporadic cases despite their temporal relationship and one probable laboratory contamination by a common yet uncovered source, explaining several consecutive positive cultures without infection. All isolates had high minimal inhibitory concentration (MIC) for flucytosine, the majority (14/34) was susceptible to fluconazole, and all to the other antifungal agents tested.

CONCLUSION

This method could help elucidate cases related to the opportunistic pathogen Y lipolytica.

Identification of telomerase RNAs in species of the Yarrowia clade provides insights into the co-evolution of telomerase, telomeric repeats and telomere-binding proteins

Telomeric repeats in fungi of the subphylum Saccharomycotina exhibit great inter- and intra-species variability in length and sequence. Such variations challenged telomeric DNA-binding proteins that co-evolved to maintain their functions at telomeres. Here, we compare the extent of co-variations in telomeric repeats, encoded in the telomerase RNAs (TERs), and the repeat-binding proteins from 13 species belonging to the Yarrowia clade. We identified putative TER loci, analyzed their sequence and secondary structure conservation, and predicted functional elements. Moreover, in vivo complementation assays with mutant TERs showed the functional importance of four novel TER substructures. The TER-derived telomeric repeat unit of all species, except for one, is 10 bp long and can be represented as 5′-TTNNNNAGGG-3′, with repeat sequence variations occuring primarily outside the vertebrate telomeric motif 5′-TTAGGG-3′. All species possess a homologue of the Yarrowia lipolytica Tay1 protein, YlTay1p. In vitro, YlTay1p displays comparable DNA-binding affinity to all repeat variants, suggesting a conserved role among these species. Taken together, these results add significant insights into the co-evolution of TERs, telomeric repeats and telomere-binding proteins in yeasts.

Pangloss: A Tool for Pan-Genome Analysis of Microbial Eukaryotes

Although the pan-genome concept originated in prokaryote genomics, an increasing number of eukaryote species pan-genomes have also been analysed. However, there is a relative lack of software intended for eukaryote pan-genome analysis compared to that available for prokaryotes. In a previous study, we analysed the pan-genomes of four model fungi with a computational pipeline that constructed pan-genomes using the synteny-dependent Pan-genome Ortholog Clustering Tool (PanOCT) approach. Here, we present a modified and improved version of that pipeline which we have called Pangloss. Pangloss can perform gene prediction for a set of genomes from a given species that the user provides, constructs and optionally refines a species pan-genome from that set using PanOCT, and can perform various functional characterisation and visualisation analyses of species pan-genome data. To demonstrate Pangloss's capabilities, we constructed and analysed a species pan-genome for the oleaginous yeast Yarrowialipolytica and also reconstructed a previously-published species pan-genome for the opportunistic respiratory pathogen Aspergillus fumigatus. Pangloss is implemented in Python, Perl and R and is freely available under an open source GPLv3 licence via GitHub.