Journal Article

The Minimal Eukaryotic Ribosomal DNA Units in the Primitive Red Alga <i>Cyanidioschyzon merolae</i>

Shinichiro Maruyama, Osami Misumi, Yasuyuki Ishii, Shuichi Asakawa, Atsushi Shimizu, Takashi Sasaki, Motomichi Matsuzaki, Tadasu Shin-i, Hisayoshi Nozaki, Yuji Kohara, Nobuyoshi Shimizu and Tsuneyoshi Kuroiwa

in DNA Research

Published on behalf of Kazusa DNA Research Institute

Volume 11, issue 2, pages 83-91
Published in print January 2004 | ISSN: 1340-2838
Published online January 2004 | e-ISSN: 1756-1663 | DOI:

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Cyanidioschyzon merolae is a small unicellular red alga that is considered to belong to one of the most deeply branched taxa in the plant kingdom. Its genome size is estimated to be 16.5 Mbp, one of the smallest among free-living eukaryotes. In the nucleus containing this small genome, one nucleolus is clearly observed, but the molecular basis for the intranuclear structure including ribosomal DNA organization is still unclear. We constructed a bacterial arti cial chromosome library for C. merolae 10D composed of two subsets with different insert size distributions. The two subsets have average insert sizes of 97 and 48 kb, representing 10.0- and 6.9-fold genome-equivalent coverage of the haploid genome, respectively. For application to whole-genome shotgun sequencing, the termini of each clone were sequenced as sequence-tagged connectors and mapped on the contigs assigned to chromosomes. Screening for rRNA genes by conventional colony hybridization with high-density filter blots and subsequent sequencing revealed that the C. merolae genome contained the smallest number of ribosomal DNA units among all the eukaryotes examined to date. They consist of only 3 single units of rRNA genes distributed on separate chromosomal loci, representing an implication for concerted evolution. Based on these results, the origin and evolution of the nucleolus are discussed.

Keywords: BAC library; Genome organization; Nucleolus

Journal Article.  0 words. 

Subjects: Genetics and Genomics

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