title: Low-affinity cation transporter (OsLCT1) regulates cadmium transport into rice grains.
abstract: Accumulation of cadmium (Cd) in rice (Oryza sativa L.) grains poses a potential health problem, especially in Asia. Most Cd in rice grains accumulates through phloem transport, but the molecular mechanism of this transport has not been revealed. In this study, we identified a rice Cd transporter, OsLCT1, involved in Cd transport to the grains. OsLCT1-GFP was localized at the plasma membrane in plant cells, and OsLCT1 showed Cd efflux activity in yeast. In rice plants, strong OsLCT1 expression was observed in leaf blades and nodes during the reproductive stage. In the uppermost node, OsLCT1 transcripts were detected around large vascular bundles and in diffuse vascular bundles. RNAi-mediated knockdown of OsLCT1 did not affect xylem-mediated Cd transport but reduced phloem-mediated Cd transport. The knockdown plants of OsLCT1 accumulated approximately half as much Cd in the grains as did the control plants. The content of other metals in rice grains and plant growth were not negatively affected by OsLCT1 suppression. These results suggest that OsLCT1 functions at the nodes in Cd transport into grains and that in a standard japonica cultivar, the regulation of OsLCT1 enables the generation of "low-Cd rice" without negative effects on agronomical traits. These findings identify a transporter gene for phloem Cd transport in plants.
authors.affiliation: Biotechnology Research Center and Graduate School of Agricultural and Life Sciences,  University of Tokyo, Tokyo 113-8657,  Japan.
authors.forename: Shimpei
authors.initials: S
authors.lastname: Uraguchi
authors.forename: Takehiro
authors.initials: T
authors.lastname: Kamiya
authors.forename: Takuya
authors.initials: T
authors.lastname: Sakamoto
authors.forename: Koji
authors.initials: K
authors.lastname: Kasai
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Sato
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Nagamura
authors.forename: Akiko
authors.initials: A
authors.lastname: Yoshida
authors.forename: Junko
authors.initials: J
authors.lastname: Kyozuka
authors.forename: Satoru
authors.initials: S
authors.lastname: Ishikawa
authors.forename: Toru
authors.initials: T
authors.lastname: Fujiwara
mesh_terms: D001692:Biological Transport; D002104:Cadmium / Q000378:metabolism / Q000493:pharmacokinetics*; D027682:Cation Transport Proteins / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D004785:Environmental Pollutants / Q000378:metabolism / Q000493:pharmacokinetics*; D055785:Gene Knockdown Techniques; D017403:In Situ Hybridization; D013058:Mass Spectrometry; D012275:Oryza / Q000378:metabolism*; D052585:Phloem / Q000378:metabolism; D034622:RNA Interference; D060888:Real-Time Polymerase Chain Reaction; D012441:Saccharomyces cerevisiae; D012639:Seeds / Q000378:metabolism*
chemical_list: D027682:Cation Transport Proteins; D004785:Environmental Pollutants; D002104:Cadmium