Causes for the Large Genome Size in a Cyanobacterium Anabaena sp. PCC7120

Nobuyoshi Sugaya[1] (
Makihiko Sato[1],[2] (
Hiroo Murakami[1] (
Akira Imaizumi[1],[3] (
Sachiyo Aburatani[1] (
Katsuhisa Horimoto[1] (

[1]Laboratory of Biostatistics, Human Genome Center, Institute of Medical Science, Universityof Tokyo, 4-6-1 Shirokane-dai, Minato-ku, Tokyo 108-8639, Japan
[2]Computer Science and Engineering Centre, Fujitsu Ltd., 1-9-3 Nakase, Mihama-ku, Chiba City, Chiba 261-8588, Japan
[3]Advanced Technology Department, Fermentation and Biotechnology Laboratories, AJINOMOTOCO., INC., 1-1 Suzuki-cho, Kawasaki-ku, Kawasaki-shi 210-8681, Japan


Three possible causes responsible for the large genome size of a cyanobacterium Anabaena sp. PCC7120 are investigated: 1) sequential tandem duplications of gene segments, genes or genomic segments, 2) horizontal gene transfers from other organisms, and 3) whole-genome duplication. We evaluated the frequency distribution of angles between paralog locations for the possibility 1), the fraction of genes deviated in GC content, GC skew, AT skew and codon adaptation index for the 2) and the gene-configuration comparison of paralogs for the 3). As a result, the possibility 3), the whole-genome duplication, was more reasonable as a molecular cause than the other causes for the large genome size in Anabaena sp. PCC7120. In addition, the whole-genome duplication was supported by the analysis of distribution pattern of protein genes with respect to functional categories.

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Japanese Society for Bioinformatics