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.

Seeing is better than believing: visualization of membrane transport in plants

“…Recently, polar auxin transport of Arabidopsis stem segments was visualized by detecting 14 C-IAA with a double-sided silicon strip detector [71]. In recent years, the micro-autoradiography method (MAR) has been established to visualize the distribution of 109 Cd and 33 P within sections of rice tissues [72]. Currently, only fixed material can be used, preventing any dynamic information about substrate distributions.…”

“…Currently, only fixed material can be used, preventing any dynamic information about substrate distributions. As 14 C (and 3 H) emit beta particles at very low energy, most transport substrates could be labelled with suitable isotopes for autoradiography, which would expand the application properties of MAR (Figure 2; [72]).…”

Agricultural aspects of radiocontamination induced by the Fukushima nuclear accident — A survey of studies by the Univ. of Tokyo Agricultural Dept. (2011–2016)

“…To study the distribution of radioactive Cs in greater detail, a microautography method was employed that had previously been developed in our laboratory. 27) After the grain was sliced, a film emulsion was painted on the surface of the glass to produce a thin film. The film was exposed to radiation from the sample and then developed to obtain a microradiograph.…”

Research with radiation and radioisotopes to better understand plant physiology and agricultural consequences of radioactive contamination from the Fukushima Daiichi nuclear accident

“…Development of radioisotope imaging (RI) systems [61][62][63][64][65][66][67][68][69][70][71][72][73][74][75][76][77][78][79][80] Two types of the real-time RI imaging system, namely macroscopic and microscopic, were developed. Both systems are designed to use conventional RI so that it is possible to perform imaging in our laboratory and not at special laboratory with special facilities.…”