Emmelien Vancaester

Title: 
PhD student
Project: 
Diatom comparative genomics

Publications

  1. Pollier, J., Vancaester, E., Kuzhiumparambil, U., Vickers, C. E., Vandepoele, K., Goossens, A., & Fabris, M. (2019). A widespread alternative squalene epoxidase participates in eukaryote steroid biosynthesis. NATURE MICROBIOLOGY, 4(2), 226–233.
    Steroids are essential triterpenoid molecules that are present in all eukaryotes and modulate the fluidity and flexibility of cell membranes. Steroids also serve as signalling molecules that are crucial for growth, development and differentiation of multicellular organisms1-3. The steroid biosynthetic pathway is highly conserved and is key in eukaryote evolution4-7. The flavoprotein squalene epoxidase (SQE) catalyses the first oxygenation reaction in this pathway and is rate limiting. However, despite its conservation in animals, plants and fungi, several phylogenetically widely distributed eukaryote genomes lack an SQE-encoding gene7,8. Here, we discovered and characterized an alternative SQE (AltSQE) belonging to the fatty acid hydroxylase superfamily. AltSQE was identified through screening of a gene library of the diatom Phaeodactylum tricornutum in a SQE-deficient yeast. In accordance with its divergent protein structure and need for cofactors, we found that AltSQE is insensitive to the conventional SQE inhibitor terbinafine. AltSQE is present in many eukaryotic lineages but is mutually exclusive with SQE and shows a patchy distribution within monophyletic clades. Our discovery provides an alternative element for the conserved steroid biosynthesis pathway, raises questions about eukaryote metabolic evolution and opens routes to develop selective SQE inhibitors to control hazardous organisms.
  2. Krasovec, M., Vancaester, E., Rombauts, S., Bucchini, F., Yau, S., Hemon, C., Lebredonchel, H., et al. (2018). Genome analyses of the microalga Picochlorum provide insights into the evolution of thermotolerance in the green lineage. GENOME BIOLOGY AND EVOLUTION, 10(9), 2347–2365.
    While the molecular events involved in cell responses to heat stress have been extensively studied, our understanding of the genetic basis of basal thermotolerance, and particularly its evolution within the green lineage, remains limited. Here, we present the 13.3-Mb haploid genome and transcriptomes of a halotolerant and thermotolerant unicellular green alga, Picochlorum costavermella (Trebouxiophyceae) to investigate the evolution of the genomic basis of thermotolerance. Differential gene expression at high and standard temperatures revealed that more of the gene families containing up-regulated genes at high temperature were recently evolved, and less originated at the ancestor of green plants. Inversely, there was an excess of ancient gene families containing transcriptionally repressed genes. Interestingly, there is a striking overlap between the thermotolerance and halotolerance transcriptional rewiring, as more than one-third of the gene families up-regulated at 35 degrees C were also up-regulated under variable salt concentrations in Picochlorum SE3. Moreover, phylogenetic analysis of the 9,304 protein coding genes revealed 26 genes of horizontally transferred origin in P. costavermella, of which five were differentially expressed at higher temperature. Altogether, these results provide new insights about how the genomic basis of adaptation to halo- and thermotolerance evolved in the green lineage.
  3. De Clerck, Olivier, Kao, S.-M., Bogaert, K., Blomme, J., Foflonker, F., Kwantes, M., Vancaester, E., et al. (2018). Insights into the evolution of multicellularity from the sea lettuce genome. CURRENT BIOLOGY, 28(18), 2921–2933.
    We report here the 98.5 Mbp haploid genome (12,924 protein coding genes) of Ulva mutabilis, a ubiquitous and iconic representative of the Ulvophyceae or green seaweeds. Ulva's rapid and abundant growth makes it a key contributor to coastal biogeochemical cycles; its role in marine sulfur cycles is particularly important because it produces high levels of dimethylsulfoniopropionate (DMSP), the main precursor of volatile dimethyl sulfide (DMS). Rapid growth makes Ulva attractive biomass feedstock but also increasingly a driver of nuisance "green tides." Ulvophytes are key to understanding the evolution of multicellularity in the green lineage, and Ulva morphogenesis is dependent on bacterial signals, making it an important species with which to study cross-kingdom communication. Our sequenced genome informs these aspects of ulvophyte cell biology, physiology, and ecology. Gene family expansions associated with multicellularity are distinct from those of freshwater algae. Candidate genes, including some that arose following horizontal gene transfer from chromalveolates, are present for the transport and metabolism of DMSP. The Ulva genome offers, therefore, new opportunities to understand coastal and marine ecosystems and the fundamental evolution of the green lineage.
  4. Van Bel, M., Diels, T., Vancaester, E., Kreft, L., Botzki, A., Van de Peer, Y., Coppens, F., et al. (2018). PLAZA 4.0 : an integrative resource for functional, evolutionary and comparative plant genomics. NUCLEIC ACIDS RESEARCH, 46(D1), D1190–D1196.
    PLAZA (https://bioinformatics.psb.ugent.be/plaza) is a plant-oriented online resource for comparative, evolutionary and functional genomics. The PLAZA platform consists of multiple independent instances focusing on different plant clades, while also providing access to a consistent set of reference species. Each PLAZA instance contains structural and functional gene annotations, gene family data and phylogenetic trees and detailed gene colinearity information. A user-friendly web interface makes the necessary tools and visualizations accessible, specific for each data type. Here we present PLAZA 4.0, the latest iteration of the PLAZA framework. This version consists of two new instances (Dicots 4.0 and Monocots 4.0) providing a large increase in newly available species, and offers access to updated and newly implemented tools and visualizations, helping users with the ever-increasing demands for complex and in-depth analyzes. The total number of species across both instances nearly doubles from 37 species in PLAZA 3.0 to 71 species in PLAZA 4.0, with a much broader coverage of crop species (e.g. wheat, palm oil) and species of evolutionary interest (e.g. spruce, Marchantia). The new PLAZA instances can also be accessed by a programming interface through a RESTful web service, thus allowing bioinformaticians to optimally leverage the power of the PLAZA platform.
  5. Zaremba-Niedzwiedzka, K., Caceres, E. F., Saw, J. H., Bäckström, D., Juzokaite, L., Vancaester, E., Seitz, K. W., et al. (2017). Asgard archaea illuminate the origin of eukaryotic cellular complexity. NATURE, 541(7637), 353–358.
    The origin and cellular complexity of eukaryotes represent a major enigma in biology. Current data support scenarios in which an archaeal host cell and an alphaproteobacterial (mitochondrial) endosymbiont merged together, resulting in the first eukaryotic cell. The host cell is related to Lokiarchaeota, an archaeal phylum with many eukaryotic features. The emergence of the structural complexity that characterizes eukaryotic cells remains unclear. Here we describe the 'Asgard' superphylum, a group of uncultivated archaea that, as well as Lokiarchaeota, includes Thor-, Odin- and Heimdallarchaeota. Asgard archaea affiliate with eukaryotes in phylogenomic analyses, and their genomes are enriched for proteins formerly considered specific to eukaryotes. Notably, thorarchaeal genomes encode several homologues of eukaryotic membrane-trafficking machinery components, including Sec23/24 and TRAPP domains. Furthermore, we identify thorarchaeal proteins with similar features to eukaryotic coat proteins involved in vesicle biogenesis. Our results expand the known repertoire of 'eukaryote-specific' proteins in Archaea, indicating that the archaeal host cell already contained many key components that govern eukaryotic cellular complexity.