title: Unexpected link between polyketide synthase and calcium carbonate biomineralization.
abstract: BACKGROUND
  Calcium carbonate biominerals participate in diverse physiological functions. Despite intensive studies, little is known about how mineralization is initiated in organisms.
  
  
  RESULTS
  We analyzed the medaka spontaneous mutant, ha, defective in otolith (calcareous ear stone) formation. ha lacks a trigger for otolith mineralization, and the causative gene was found to encode polyketide synthase (pks), a multifunctional enzyme mainly found in bacteria, fungi, and plant. Subsequent experiments demonstrate that the products of medaka PKS, most likely polyketides or their derivatives, act as nucleation facilitators in otolith mineralization. The generality of this novel PKS function is supported by the essential role of echinoderm PKS in calcareous skeleton formation together with the presence of PKSs in a much wider range of animals from coral to vertebrates.
  
  
  CONCLUSIONS
  The present study first links PKS to biomineralization and provides a genetic cue for biogeochemistry of carbon and calcium cycles.
authors.affiliation: Department of Biological Sciences, Graduate School of Science, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 Japan ; Present address: Department of Pharmaceutical and Environmental Sciences, Tokyo Metropolitan Institute of Public Health, 3-24-1, Hyakunincho, Shinju-ku, Tokyo 169-0073 Japan.
authors.forename: Motoki
authors.initials: M
authors.lastname: Hojo
authors.affiliation: Department of Biological Sciences, Graduate School of Science, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 Japan ; Present address: Division of Molecular Pathology, Research Institute for Biomedical Sciences, Tokyo University of Science, 2669 Yamazaki, Noda, Chiba 278-0022 Japan.
authors.forename: Ai
authors.initials: A
authors.lastname: Omi
authors.affiliation: Tateyama Marine Laboratory, Marine and Coastal Research Center, Ochanomizu University, Kou-yatsu 11, Tateyama, Chiba 294-0301 Japan.
authors.forename: Gen
authors.initials: G
authors.lastname: Hamanaka
authors.affiliation: Department of Food and Nutrition, Japan Women's University, 2-8-1, Mejirodai, Bunkyo-ku, Tokyo 112-8681 Japan.
authors.forename: Kazutoshi
authors.initials: K
authors.lastname: Shindo
authors.affiliation: Department of Biological Sciences, Graduate School of Science, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 Japan.
authors.forename: Atsuko
authors.initials: A
authors.lastname: Shimada
authors.affiliation: Misaki Marine Biological Station, Graduate School of Science, University of Tokyo, 1024 Koajiro, Misaki, Miura, Kanagawa 238-0225 Japan.
authors.forename: Mariko
authors.initials: M
authors.lastname: Kondo
authors.affiliation: Department of Biological Sciences, Graduate School of Science, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 Japan ; Present address: Laboratory of Veterinary Biochemistry, Nihon University College of Bioresource Sciences, 1866 Kameino, Fujisawa, Kanagawa 252-0880 Japan.
authors.forename: Takanori
authors.initials: T
authors.lastname: Narita
authors.affiliation: Tateyama Marine Laboratory, Marine and Coastal Research Center, Ochanomizu University, Kou-yatsu 11, Tateyama, Chiba 294-0301 Japan.
authors.forename: Masato
authors.initials: M
authors.lastname: Kiyomoto
authors.affiliation: Department of Biotechnology, Graduate School of Agricultural and Life Sciences, University of Tokyo, 1-1-1, Yayoi, Bunkyo-ku, Tokyo 113-8657 Japan.
authors.forename: Yohei
authors.initials: Y
authors.lastname: Katsuyama
authors.affiliation: Department of Biotechnology, Graduate School of Agricultural and Life Sciences, University of Tokyo, 1-1-1, Yayoi, Bunkyo-ku, Tokyo 113-8657 Japan.
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Ohnishi
authors.affiliation: Department of Biological Sciences, Graduate School of Science, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 Japan.
authors.forename: Naoki
authors.initials: N
authors.lastname: Irie
authors.affiliation: Department of Biological Sciences, Graduate School of Science, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Takeda
keywords: Biomineralization; Calcium carbonate; Medaka; Otolith; Polyketide synthase; Spicule