Pathogen Genomics Laboratory, Biological and Environmental Sciences and Engineering Division, King Abdullah University of Science and Technology, Thuwal, Saudi Arabia.
Parasite Genomics, Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Cambridge, United Kingdom.
Department of Cell Biology, University of Alberta, Edmonton, Canada.
Canadian Institute for Advanced Research, Department of Botany, University of British Columbia, Vancouver, Canada.
Institute of Parasitology, Biology Centre, Czech Academy of Sciences, České Budějovice, Czech Republic.
Biochemical Sciences Division, CSIR National Chemical Laboratory, Pune, India.
Ecology and Evolutionary Biology Section, Institut de Biologie de l'Ecole Normale Supérieure, CNRS UMR8197 INSERM U1024, Paris, France.
Bioscience Core Laboratory, King Abdullah University of Science and Technology, Thuwal, Saudi Arabia.
Department of Biology, University of Pennsylvania, Philadelphia, United States.
School of Botany, University of Melbourne, Parkville, Australia.
Seattle Biomedical Research Institute, Seattle, United States.
Centro de Biología Molecular Severo Ochoa, CSIC/Universidad Autónoma de Madrid, Madrid, Spain.
Centre for GeoGenetics, Natural History Museum of Denmark, University of Copenhagen, Copenhagen, Denmark.
European Bioinformatics Institute (EMBL-EBI), Wellcome Genome Campus, Hinxton, Cambridge, United Kingdom.
Wellcome Trust Centre For Molecular Parasitology, Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom.
Broad Genome Sequencing and Analysis Program, Broad Institute of MIT and Harvard, Cambridge, United States.
Department of Microbiology, Monash University, Clayton, Australia.
Department of Microbiology and Immunology, Weill Cornell Medical College, New York, United States.
The eukaryotic phylum Apicomplexa encompasses thousands of obligate intracellular parasites of humans and animals with immense socio-economic and health impacts. We sequenced nuclear genomes of Chromera velia and Vitrella brassicaformis, free-living non-parasitic photosynthetic algae closely related to apicomplexans. Proteins from key metabolic pathways and from the endomembrane trafficking systems associated with a free-living lifestyle have been progressively and non-randomly lost during adaptation to parasitism. The free-living ancestor contained a broad repertoire of genes many of which were repurposed for parasitic processes, such as extracellular proteins, components of a motility apparatus, and DNA- and RNA-binding protein families. Based on transcriptome analyses across 36 environmental conditions, Chromera orthologs of apicomplexan invasion-related motility genes were co-regulated with genes encoding the flagellar apparatus, supporting the functional contribution of flagella to the evolution of invasion machinery. This study provides insights into how obligate parasites with diverse life strategies arose from a once free-living phototrophic marine alga.
