Eukaryote-Wide Distribution of a Family of Longin Domain-Containing GAP Complexes for Small GTPases.

Arf and Rab family small GTPases and their regulators, GTPase-activating proteins (GAPs) and guanine nucleotide exchange factors (GEFs), play a central role in membrane trafficking. In this study, we focused on a recently reported GAP for Arf (and potentially Rab) proteins, the CSW complex, a part of a small family of longin domain-containing proteins that form complexes with GAP activity. This family also includes folliculin and GATOR1, which are GAPs for the Rag/Gtr GTPases.

Prevalence and environmental abundance of the TSET complex in cosmopolitan algal groups.

Classical cell biology paradigms are largely established on animal, fungal, and plant models which constitute a small fraction of eukaryotic diversity. Some important cellular machinery has been historically overlooked due to their absence from animals and fungi, e.g.

Microbial community development in an oil sands pit lake.

Surface mining and extraction of oil sands in Canada produces fluid tailings that contain several compounds of concern for the environment. One option for mine reclamation is the construction of Pit Lakes (PLs) to contain and remediate these tailings. Ultimately, PLs should support food webs typical of boreal lakes.

Diplonemid protists possess exotic endomembrane machinery, impacting models of membrane trafficking in modern and ancient eukaryotes.

Diplonemids are among the most abundant and species-rich protists in the oceans. Marine heterotrophic flagellates, including diplonemids, have been suggested to play important roles in global biogeochemical cycles. Diplonemids are also the sister taxon of kinetoplastids, home to trypanosomatid parasites of global health importance, and thus are informative about the evolution of kinetoplastid biology.

The Asgard archaeal origins of Arf family GTPases involved in eukaryotic organelle dynamics.

The evolution of eukaryotes is a fundamental event in the history of life. The closest prokaryotic lineage to eukaryotes, the Asgardarchaeota, encode proteins previously found only in eukaryotes, providing insight into their archaeal ancestor. Eukaryotic cells are characterized by endomembrane organelles, and the Arf family GTPases regulate organelle dynamics by recruiting effector proteins to membranes upon activation.

Comparative Analysis of Protist Communities in Oilsands Tailings Using Amplicon Sequencing and Metagenomics.

The Canadian province of Alberta contains substantial oilsands reservoirs, consisting of bitumen, clay and sand. Extracting oil involves separating bitumen from inorganic particles using hot water and chemical diluents, resulting in liquid tailings waste with ecotoxicologically significant compounds. Ongoing efforts aim to reclaim tailings-affected areas, with protist colonisation serving as one assessment method of reclamation progress.

Reconstructing the last common ancestor of all eukaryotes.

Understanding the origin of eukaryotic cells is one of the most difficult problems in all of biology. A key challenge relevant to the question of eukaryogenesis is reconstructing the gene repertoire of the last eukaryotic common ancestor (LECA). As data sets grow, sketching an accurate genomics-informed picture of early eukaryotic cellular complexity requires provision of analytical resources and a commitment to data sharing.

A unique symbiosome in an anaerobic single-celled eukaryote.

Symbiotic relationships between eukaryotes and prokaryotes played pivotal roles in the evolution of life and drove the emergence of specialized symbiotic structures in animals, plants and fungi. The host-evolved symbiotic structures of microbial eukaryotes - the vast majority of such hosts in nature - remain largely unstudied. Here we describe highly structured symbiosomes within three free-living anaerobic protists (Anaeramoeba spp.

An evolutionary perspective on Arf family GTPases.

The Arf family GTPases are regulators of eukaryotic cellular organization, functioning in the secretory and endocytic pathways, in cilia and flagella, in cytoskeleton dynamics, and in lipid metabolism. We describe the evolution of this protein family and its well-studied regulators. The last eukaryotic common ancestor had fifteen members, and the current complement of Arf GTPases has been sculpted by gene loss and gene duplications since that point.

Evolutionary origins of the lysosome-related organelle sorting machinery reveal ancient homology in post-endosome trafficking pathways.

The major organelles of the endomembrane system were in place by the time of the last eukaryotic common ancestor (LECA) (~1.5 billion years ago). Their acquisitions were defining milestones during eukaryogenesis.

The retromer and retriever systems are conserved and differentially expanded in parabasalids.

Early endosomes sort transmembrane cargo either for lysosomal degradation or retrieval to the plasma membrane or the Golgi complex. Endosomal retrieval in eukaryotes is governed by the anciently homologous retromer or retriever complexes. Each comprises a core tri-protein subcomplex, membrane-deformation proteins and interacting partner complexes, together retrieving a variety of known cargo proteins.

Contractile vacuoles: a rapidly expanding (and occasionally diminishing?) understanding.

Osmoregulation is the homeostatic mechanism essential for the survival of organisms in hypoosmotic and hyperosmotic conditions. In freshwater or soil dwelling protists this is frequently achieved through the action of an osmoregulatory organelle, the contractile vacuole. This endomembrane organelle responds to the osmotic challenges and compensates by collecting and expelling the excess water to maintain the cellular osmolarity.

Phytoplankton ecology in the early years of a boreal oil sands end pit lake.

Background: Base Mine Lake (BML) is the first full-scale end pit lake for the oil sands mining industry in Canada. BML sequesters oil sands tailings under a freshwater cap and is intended to develop into a functional ecosystem that can be integrated into the local watershed. The first stage of successful reclamation requires the development of a phytoplankton community supporting a typical boreal lake food web.

Genomic survey maps differences in the molecular complement of vesicle formation machinery between Giardia intestinalis assemblages.

Giardia intestinalis is a globally important microbial pathogen with considerable public health, agricultural, and economic burden. Genome sequencing and comparative analyses have elucidated G. intestinalis to be a taxonomically diverse species consisting of at least eight different sub-types (assemblages A-H) that can infect a great variety of animal hosts, including humans.

Genomics of Preaxostyla Flagellates Illuminates the Path Towards the Loss of Mitochondria.

The notion that mitochondria cannot be lost was shattered with the report of an oxymonad Monocercomonoides exilis, the first eukaryote arguably without any mitochondrion. Yet, questions remain about whether this extends beyond the single species and how this transition took place. The Oxymonadida is a group of gut endobionts taxonomically housed in the Preaxostyla which also contains free-living flagellates of the genera Trimastix and Paratrimastix.

One high quality genome and two transcriptome datasets for new species of Mantamonas, a deep-branching eukaryote clade.

Mantamonads were long considered to represent an "orphan" lineage in the tree of eukaryotes, likely branching near the most frequently assumed position for the root of eukaryotes. Recent phylogenomic analyses have placed them as part of the "CRuMs" supergroup, along with collodictyonids and rigifilids. This supergroup appears to branch at the base of Amorphea, making it of special importance for understanding the deep evolutionary history of eukaryotes.

Lessons from the deep: mechanisms behind diversification of eukaryotic protein complexes.

Genetic variation is the major mechanism behind adaptation and evolutionary change. As most proteins operate through interactions with other proteins, changes in protein complex composition and subunit sequence provide potentially new functions. Comparative genomics can reveal expansions, losses and sequence divergence within protein-coding genes, but in silico analysis cannot detect subunit substitutions or replacements of entire protein complexes.

Functional differentiation of Sec13 paralogues in the euglenozoan protists.

The β-propeller protein Sec13 plays roles in at least three distinct processes by virtue of being a component of the COPII endoplasmic reticulum export vesicle coat, the nuclear pore complex (NPC) and the Seh1-associated (SEA)/GATOR nutrient-sensing complex. This suggests that regulatory mechanisms coordinating these cellular activities may operate Sec13. The NPC, COPII and SEA/GATOR are all ancient features of eukaryotic cells, and in the vast majority of eukaryotes, a single Sec13 gene is present.

Evolutionary analysis of cellular reduction and anaerobicity in the hyper-prevalent gut microbe Blastocystis.

Blastocystis is the most prevalent microbial eukaryote in the human and animal gut, yet its role as commensal or parasite is still under debate. Blastocystis has clearly undergone evolutionary adaptation to the gut environment and possesses minimal cellular compartmentalization, reduced anaerobic mitochondria, no flagella, and no reported peroxisomes. To address this poorly understood evolutionary transition, we have taken a multi-disciplinary approach to characterize Proteromonas lacertae, the closest canonical stramenopile relative of Blastocystis.

Stable endocytic structures navigate the complex pellicle of apicomplexan parasites.

Apicomplexan parasites have immense impacts on humanity, but their basic cellular processes are often poorly understood. Where endocytosis occurs in these cells, how conserved this process is with other eukaryotes, and what the functions of endocytosis are across this phylum are major unanswered questions. Using the apicomplexan model Toxoplasma, we identified the molecular composition and behavior of unusual, fixed endocytic structures.

Ancient and pervasive expansion of adaptin-related vesicle coat machinery across Parabasalia.

The eukaryotic phylum Parabasalia is composed primarily of anaerobic, endobiotic organisms such as the veterinary parasite Tritrichomonas foetus and the human parasite Trichomonas vaginalis, the latter causing the most prevalent, non-viral, sexually transmitted disease world-wide. Although a parasitic lifestyle is generally associated with a reduction in cell biology, T. vaginalis provides a striking counter-example.

Endosomal vesicle fusion machinery is involved with the contractile vacuole in Dictyostelium discoideum.

Contractile vacuoles (CVs), enigmatic osmoregulatory organelles, share common characteristics, such as a requirement for RAB11 and high levels of V-ATPase. These commonalities suggest a conserved evolutionary origin for the CVs with implications for understanding of the last common ancestor of eukaryotes and eukaryotic diversification more broadly. A taxonomically broader sampling of CV-associated machinery is required to address this question further.