title: Genome sequence and gene compaction of the eukaryote parasite Encephalitozoon cuniculi.
abstract: Microsporidia are obligate intracellular parasites infesting many animal groups. Lacking mitochondria and peroxysomes, these unicellular eukaryotes were first considered a deeply branching protist lineage that diverged before the endosymbiotic event that led to mitochondria. The discovery of a gene for a mitochondrial-type chaperone combined with molecular phylogenetic data later implied that microsporidia are atypical fungi that lost mitochondria during evolution. Here we report the DNA sequences of the 11 chromosomes of the approximately 2.9-megabase (Mb) genome of Encephalitozoon cuniculi (1,997 potential protein-coding genes). Genome compaction is reflected by reduced intergenic spacers and by the shortness of most putative proteins relative to their eukaryote orthologues. The strong host dependence is illustrated by the lack of genes for some biosynthetic pathways and for the tricarboxylic acid cycle. Phylogenetic analysis lends substantial credit to the fungal affiliation of microsporidia. Because the E. cuniculi genome contains genes related to some mitochondrial functions (for example, Fe-S cluster assembly), we hypothesize that microsporidia have retained a mitochondrion-derived organelle.
authors.affiliation: Genoscope, UMR CNRS 8030, CP 5706, 91057 Evry cedex, France.
authors.forename: M D
authors.initials: MD
authors.lastname: Katinka
authors.forename: S
authors.initials: S
authors.lastname: Duprat
authors.forename: E
authors.initials: E
authors.lastname: Cornillot
authors.forename: G
authors.initials: G
authors.lastname: Méténier
authors.forename: F
authors.initials: F
authors.lastname: Thomarat
authors.forename: G
authors.initials: G
authors.lastname: Prensier
authors.forename: V
authors.initials: V
authors.lastname: Barbe
authors.forename: E
authors.initials: E
authors.lastname: Peyretaillade
authors.forename: P
authors.initials: P
authors.lastname: Brottier
authors.forename: P
authors.initials: P
authors.lastname: Wincker
authors.forename: F
authors.initials: F
authors.lastname: Delbac
authors.forename: H
authors.initials: H
authors.lastname: El Alaoui
authors.forename: P
authors.initials: P
authors.lastname: Peyret
authors.forename: W
authors.initials: W
authors.lastname: Saurin
authors.forename: M
authors.initials: M
authors.lastname: Gouy
authors.forename: J
authors.initials: J
authors.lastname: Weissenbach
authors.forename: C P
authors.initials: CP
authors.lastname: Vivarès
mesh_terms: D000818:Animals; D005075:Biological Evolution; D001692:Biological Transport; D016054:DNA, Protozoan; D009670:Encephalitozoon cuniculi / Q000235:genetics* / Q000378:metabolism / Q000648:ultrastructure; D018503:Genome, Protozoan; D051379:Mice; D008928:Mitochondria / Q000235:genetics; D008969:Molecular Sequence Data; D015800:Protozoan Proteins / Q000235:genetics / Q000378:metabolism; D017422:Sequence Analysis, DNA
chemical_list: D016054:DNA, Protozoan; D015800:Protozoan Proteins