title: A microautoradiographic method for fresh-frozen sections to reveal the distribution of radionuclides at the cellular level in plants.
abstract: Microautoradiography (MAR) is a conventional imaging method based on the daguerreotype. The technique is used to visualize the distribution of radionuclide-labeled compounds within a tissue section. However, application of the classical MAR method to plant tissue sections is associated with several difficulties. In this study, we report an MAR method applicable to fresh-frozen plant sections. Our method had two features: (i) the sample was kept frozen from plant tissue collection to radioisotope detection, making it possible to fix solutes without solvent exchange; and (ii) 1.2 µm thick polyphenylene sulfide film was inserted between the fresh-frozen plant section and the photosensitive nuclear emulsion to separate the section from the emulsion before autoradiography was conducted, which significantly improved the quality of the section until microscopic detection, the quality of the MAR image and the success rate. Then, the passage of cadmium (Cd) through vegetative rice stem tissue after 24 h of (109)Cd absorption was described for the first time using the MAR method. MAR clearly revealed the distribution of (109)Cd at the tissue level with high resolution. The (109)Cd concentration in phloem cells was found to be particularly high, whereas the xylem cells contained only small amounts of (109)Cd. The MAR method was also applicable for detecting (109)Cd and [(33)P]phosphate in roots. The MAR method developed here is expected to provide distribution images for a variety of compounds and ions in plant tissue.
authors.affiliation: Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, 113-8657 Japan.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Hirose
authors.affiliation: Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, 113-8657 Japan.
authors.forename: Natsuko I
authors.initials: NI
authors.lastname: Kobayashi
authors.affiliation: Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, 113-8657 Japan uktanoi@mail.ecc.u-tokyo.ac.jp.
authors.forename: Keitaro
authors.initials: K
authors.lastname: Tanoi
authors.affiliation: Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, 113-8657 Japan.
authors.forename: Tomoko M
authors.initials: TM
authors.lastname: Nakanishi
mesh_terms: D001345:Autoradiography / Q000379:methods*; D001692:Biological Transport; D019256:Cadmium Chloride / Q000378:metabolism; D002106:Cadmium Radioisotopes / Q000032:analysis; D005629:Frozen Sections; D008852:Microradiography / Q000379:methods*; D012275:Oryza / Q000166:cytology* / Q000378:metabolism; D010710:Phosphates / Q000378:metabolism; D010761:Phosphorus Radioisotopes / Q000032:analysis; D018517:Plant Roots / Q000166:cytology / Q000378:metabolism; D018520:Plant Shoots / Q000166:cytology / Q000378:metabolism; D011868:Radioisotopes / Q000032:analysis; D052584:Xylem / Q000166:cytology / Q000378:metabolism
chemical_list: D002106:Cadmium Radioisotopes; D010710:Phosphates; D010761:Phosphorus Radioisotopes; D011868:Radioisotopes; D019256:Cadmium Chloride
keywords: Cadmium; Imaging; Microautoradiography; Oryza sativa; Phosphate; Transport