title: Ion-beam irradiation, gene identification, and marker-assisted breeding in the development of low-cadmium rice.
abstract: Rice (Oryza sativa L.) grain is a major dietary source of cadmium (Cd), which is toxic to humans, but no practical technique exists to substantially reduce Cd contamination. Carbon ion-beam irradiation produced three rice mutants with <0.05 mg Cd⋅kg(-1) in the grain compared with a mean of 1.73 mg Cd⋅kg(-1) in the parent, Koshihikari. We identified the gene responsible for reduced Cd uptake and developed a strategy for marker-assisted selection of low-Cd cultivars. Sequence analysis revealed that these mutants have different mutations of the same gene (OsNRAMP5), which encodes a natural resistance-associated macrophage protein. Functional analysis revealed that the defective transporter protein encoded by the mutant osnramp5 greatly decreases Cd uptake by roots, resulting in decreased Cd in the straw and grain. In addition, we developed DNA markers to facilitate marker-assisted selection of cultivars carrying osnramp5. When grown in Cd-contaminated paddy fields, the mutants have nearly undetectable Cd in their grains and exhibit no agriculturally or economically adverse traits. Because mutants produced by ion-beam radiation are not transgenic plants, they are likely to be accepted by consumers and thus represent a practical choice for rice production worldwide.
authors.affiliation: Soil Environment Division, National Institute for Agro-Environmental Sciences, Tsukuba, Ibaraki 305-8604, Japan. isatoru@affrc.go.jp
authors.forename: Satoru
authors.initials: S
authors.lastname: Ishikawa
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Ishimaru
authors.forename: Masato
authors.initials: M
authors.lastname: Igura
authors.forename: Masato
authors.initials: M
authors.lastname: Kuramata
authors.forename: Tadashi
authors.initials: T
authors.lastname: Abe
authors.forename: Takeshi
authors.initials: T
authors.lastname: Senoura
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Hase
authors.forename: Tomohito
authors.initials: T
authors.lastname: Arao
authors.forename: Naoko K
authors.initials: NK
authors.lastname: Nishizawa
authors.forename: Hiromi
authors.initials: H
authors.lastname: Nakanishi
mesh_terms: D000383:Agriculture; D001483:Base Sequence; D001947:Breeding; D002104:Cadmium / Q000378:metabolism*; D002244:Carbon / Q000737:chemistry*; D003001:Cloning, Molecular; D017343:Genes, Plant / Q000235:genetics*; D005819:Genetic Markers; D006801:Humans; D007477:Ions; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D019697:Onions / Q000166:cytology / Q000235:genetics; D012275:Oryza / Q000235:genetics* / Q000254:growth & development* / Q000528:radiation effects; D019441:Plant Epidermis / Q000166:cytology / Q000378:metabolism; D010940:Plant Proteins / Q000378:metabolism; D021381:Protein Transport / Q000528:radiation effects; D019655:Quantitative Trait, Heritable; D012639:Seeds / Q000378:metabolism / Q000528:radiation effects; D013347:Subcellular Fractions / Q000378:metabolism / Q000528:radiation effects; D014170:Transformation, Genetic
chemical_list: D005819:Genetic Markers; D007477:Ions; D010940:Plant Proteins; D002104:Cadmium; D002244:Carbon