Imaging Salt Uptake Dynamics in Plants Using PET

Abstract

Soil salinity is a global environmental challenge for crop production. Understanding the uptake and transport properties of salt in plants is crucial to evaluate their potential for growth in high salinity soils and as a basis for engineering varieties with increased salt tolerance. Positron emission tomography (PET), traditionally used in medical and animal imaging applications for assessing and quantifying the dynamic bio-distribution of molecular species, has the potential to provide useful measurements of salt transport dynamics in an intact plant. Here we report on the feasibility of studying the dynamic transport of 22Na in millet using PET. Twenty-four green foxtail (Setaria viridis L. Beauv.) plants, 12 of each of two different accessions, were incubated in a growth solution containing 22Na+ ions and imaged at 5 time points over a 2-week period using a high-resolution small animal PET scanner. The reconstructed PET images showed clear evidence of sodium transport throughout the whole plant over time. Quantitative region-of-interest analysis of the PET data confirmed a strong correlation between total 22Na activity in the plants and time. Our results showed consistent salt transport dynamics within plants of the same variety and important differences between the accessions. These differences were corroborated by independent measurement of Na+ content and expression of the NHX transcript, a gene implicated in sodium transport. Our results demonstrate that PET can be used to quantitatively evaluate the transport of sodium in plants over time and, potentially, to discern differing salt-tolerance properties between plant varieties. In this paper, we also address the practical radiation safety aspects of working with 22Na in the context of plant imaging and describe a robust pipeline for handling and incubating plants. We conclude that PET is a promising and practical candidate technology to complement more traditional salt analysis methods and provide insights into systems-level salt transport mechanisms in intact plants.

Morpho-physiological and gene expression responses of wheat byAegilops cylindricaamphidiploids to salt stress

“…K + / Na + ratio has been recognized as a critical physiological mechanism that contributes to the overall salt tolerance of plants (Rubio et al 2020); in this mechanism Na + does not accumulate to toxic levels in the leaves by discriminately excluding Na + but accumulating K + in the cells (Arabbeigi et al 2014;Kiani et al 2015;Shabala et al 2013;Zhu et al 2016). Recently, Arino-estrada et al (2019) used the positron emission tomography (PET) to demonstrate the dynamic uptake and transport of Na in seedlings and to reveal the significant genetic diversity in terms of salt transport.…”

Design Study of a Novel Positron Emission Tomography System for Plant Imaging

“…Conventional preclinical and clinical systems are developed with a horizontal extension of the FOV due to the supine position of small animals and patients during a PET scan. Several efforts on plant PET investigations have been made so far using conventional scanners (Ariño-Estrada et al, 2019 ; Ruwanpathirana et al, 2021 ) but with samples positioned vertically inside the camera: the plant displacement along the radial direction of the FOV causes non-uniformity in terms of spatial resolution. However, there are few attempts of PET scanners with the FOV extended in vertical that are conquering a niche in the field of personalized bioimaging (Norvall et al, 2021 ; Sakai et al, 2021 ).…”

Non-invasive radionuclide imaging of trace metal trafficking in health and disease: “PET metallomics”

“…Several radioisotopes of sodium are available, but few have radiological properties that support imaging. 22 Na (b + , t 1/2 = 2.6 years) has been used to image sodium transport in plants, [11][12][13] but has seen limited use in humans due to its long half-life which results in high radiation absorbed dose to subjects receiving it. 24 Na (b À , t 1/2 = 15 hours) has a shorter half-life that is more suited to studying sodium trafficking, but its poorlypenetrating beta emission limits its use to in vitro measurements with a beta detector.…”