title: Grain accumulation of selenium species in rice (Oryza sativa L.).
abstract: Efficient Se biofortification programs require a thorough understanding of the accumulation and distribution of Se species within the rice grain. Therefore, the translocation of Se species to the filling grain and their spatial unloading were investigated. Se species were supplied via cut flag leaves of intact plants and excised panicle stems subjected to a ± stem-girdling treatment during grain fill. Total Se concentrations in the flag leaves and grain were quantified by inductively coupled plasma mass spectrometry. Spatial accumulation was investigated using synchrotron X-ray fluorescence microtomography. Selenomethionine (SeMet) and selenomethylcysteine (SeMeSeCys) were transported to the grain more efficiently than selenite and selenate. SeMet and SeMeSeCys were translocated exclusively via the phloem, while inorganic Se was transported via both the phloem and xylem. For SeMet- and SeMeSeCys-fed grain, Se dispersed throughout the external grain layers and into the endosperm and, for SeMeSeCys, into the embryo. Selenite was retained at the point of grain entry. These results demonstrate that the organic Se species SeMet and SeMeSeCys are rapidly loaded into the phloem and transported to the grain far more efficiently than inorganic species. Organic Se species are distributed more readily, and extensively, throughout the grain than selenite.
authors.affiliation: Institute of Biological and Environmental Sciences, University of Aberdeen, Cruickshank Building, St. Machar Drive, Aberdeen AB24 3UU, United Kingdom.
authors.forename: Anne-Marie
authors.initials: AM
authors.lastname: Carey
authors.forename: Kirk G
authors.initials: KG
authors.lastname: Scheckel
authors.forename: Enzo
authors.initials: E
authors.lastname: Lombi
authors.forename: Matt
authors.initials: M
authors.lastname: Newville
authors.forename: Yongseong
authors.initials: Y
authors.lastname: Choi
authors.forename: Gareth J
authors.initials: GJ
authors.lastname: Norton
authors.forename: Adam H
authors.initials: AH
authors.lastname: Price
authors.forename: Andrew A
authors.initials: AA
authors.lastname: Meharg
mesh_terms: D012275:Oryza / Q000378:metabolism*; D018515:Plant Leaves / Q000378:metabolism; D018547:Plant Stems / Q000378:metabolism; D012639:Seeds / Q000378:metabolism*; D012643:Selenium / Q000378:metabolism*; D017356:Synchrotrons; D055114:X-Ray Microtomography
chemical_list: D012643:Selenium