Unusually Large Number of Mutations in Asexually Reproducing Clonal Planarian Dugesia japonica: e0143525

• Published in: PloS one Vol. 10; no. 11
• Main Authors: Nishimura, Osamu, Hosoda, Kazutaka, Kawaguchi, Eri, Yazawa, Shigenobu, Hayashi, Tetsutaro, Inoue, Takeshi, Umesono, Yoshihiko, Agata, Kiyokazu
• Format: Journal Article
• Language: English
• Published: 01.11.2015
• Subjects: Dugesia japonica
• ISSN: 1932-6203
• DOI: 10.1371/journal.pone.0143525

We established a laboratory clonal strain of freshwater planarian (Dugesia japonica) that was derived from a single individual and that continued to undergo autotomous asexual reproduction for more than 20 years, and we performed large-scale genome sequencing and transcriptome analysis on it. Despite the fact that a completely clonal strain of the planarian was used, an unusually large number of mutations were detected. To enable quantitative genetic analysis of such a unique organism, we developed a new model called the Reference Gene Model, and used it to conduct large-scale transcriptome analysis. The results revealed large numbers of mutations not only outside but also inside gene-coding regions. Non-synonymous SNPs were detected in 74% of the genes for which valid ORFs were predicted. Interestingly, the high-mutation genes, such as metabolism- and defense-related genes, were correlated with genes that were previously identified as diverse genes among different planarian species. Although a large number of amino acid substitutions were apparently accumulated during asexual reproduction over this long period of time, the planarian maintained normal body-shape, behaviors, and physiological functions. The results of the present study reveal a unique aspect of asexual reproduction.