title: A 100%-complete sequence reveals unusually simple genomic features in the hot-spring red alga Cyanidioschyzon merolae.
abstract: BACKGROUND
  All previously reported eukaryotic nuclear genome sequences have been incomplete, especially in highly repeated units and chromosomal ends. Because repetitive DNA is important for many aspects of biology, complete chromosomal structures are fundamental for understanding eukaryotic cells. Our earlier, nearly complete genome sequence of the hot-spring red alga Cyanidioschyzon merolae revealed several unique features, including just three ribosomal DNA copies, very few introns, and a small total number of genes. However, because the exact structures of certain functionally important repeated elements remained ambiguous, that sequence was not complete. Obviously, those ambiguities needed to be resolved before the unique features of the C. merolae genome could be summarized, and the ambiguities could only be resolved by completing the sequence. Therefore, we aimed to complete all previous gaps and sequence all remaining chromosomal ends, and now report the first nuclear-genome sequence for any eukaryote that is 100% complete.
  
  
  RESULTS
  Our present complete sequence consists of 16546747 nucleotides covering 100% of the 20 linear chromosomes from telomere to telomere, representing the simple and unique chromosomal structures of the eukaryotic cell. We have unambiguously established that the C. merolae genome contains the smallest known histone-gene cluster, a unique telomeric repeat for all chromosomal ends, and an extremely low number of transposons.
  
  
  CONCLUSIONS
  By virtue of these attributes and others that we had discovered previously, C. merolae appears to have the simplest nuclear genome of the non-symbiotic eukaryotes. These unusually simple genomic features in the 100% complete genome sequence of C. merolae are extremely useful for further studies of eukaryotic cells.
authors.affiliation: Department of Biological Sciences, Graduate School of Science, the University of Tokyo, Tokyo, Japan. nozaki@biol.s.u-tokyo.ac.jp
authors.forename: Hisayoshi
authors.initials: H
authors.lastname: Nozaki
authors.forename: Hiroyoshi
authors.initials: H
authors.lastname: Takano
authors.forename: Osami
authors.initials: O
authors.lastname: Misumi
authors.forename: Kimihiro
authors.initials: K
authors.lastname: Terasawa
authors.forename: Motomichi
authors.initials: M
authors.lastname: Matsuzaki
authors.forename: Shinichiro
authors.initials: S
authors.lastname: Maruyama
authors.forename: Keiji
authors.initials: K
authors.lastname: Nishida
authors.forename: Fumi
authors.initials: F
authors.lastname: Yagisawa
authors.forename: Yamato
authors.initials: Y
authors.lastname: Yoshida
authors.forename: Takayuki
authors.initials: T
authors.lastname: Fujiwara
authors.forename: Susumu
authors.initials: S
authors.lastname: Takio
authors.forename: Katsunori
authors.initials: K
authors.lastname: Tamura
authors.forename: Sung Jin
authors.initials: SJ
authors.lastname: Chung
authors.forename: Soichi
authors.initials: S
authors.lastname: Nakamura
authors.forename: Haruko
authors.initials: H
authors.lastname: Kuroiwa
authors.forename: Kan
authors.initials: K
authors.lastname: Tanaka
authors.forename: Naoki
authors.initials: N
authors.lastname: Sato
authors.forename: Tsuneyoshi
authors.initials: T
authors.lastname: Kuroiwa
mesh_terms: D001483:Base Sequence; D002874:Chromosome Mapping; D004251:DNA Transposable Elements / Q000235:genetics; D048028:DNA, Algal / Q000737:chemistry / Q000235:genetics*; D005057:Eukaryotic Cells / Q000378:metabolism; D016678:Genome; D023281:Genomics / Q000379:methods; D006657:Histones / Q000235:genetics; D045482:Hot Springs / Q000382:microbiology*; D008957:Models, Genetic; D008969:Molecular Sequence Data; D005810:Multigene Family; D000461:Rhodophyta / Q000235:genetics*; D017422:Sequence Analysis, DNA; D016615:Telomere / Q000235:genetics
chemical_list: D004251:DNA Transposable Elements; D048028:DNA, Algal; D006657:Histones