Journal of Experimental Botany, Vol. 71, No. 18 pp. 5603–5614, 2020 doi:10.1093/jxb/eraa262 Advance Access Publication 28 May 2020 Abbreviations: ANOSIM, analysis of similarities; ASV, amplicon sequence variants; C1/C24, control after 1 h/24 h; GO, gene ontology; Gy, gray; PCoA, principal coordinate analysis; qRT-PCR, quantitative reverse transcription polymerase chain reaction; ROS, reactive oxygen species; X1/X24, XRCT scanned after 1 h/24 h; XRCT, X-ray computed tomography © The Author(s) 2020. Published by Oxford University Press on behalf of the Society for Experimental Biology. All rights reserved. For permissions, please email: journals.permissions@oup.com RESEARCH PAPER Compatibility of X-ray computed tomography with plant gene expression, rhizosphere bacterial communities and enzyme activities Minh Ganther 1, * , , Bunlong Yim 2, *, Zeeshan Ibrahim 1 , Manuela Desiree Bienert 3 , Eva Lippold 1 , Lorrie Maccario 4, , Søren Johannes Sørensen 4, , Gerd Patrick Bienert 3, , Doris Vetterlein 1,5, , Anna Heintz-Buschart 1,6, , Evgenia Blagodatskaya 1, , Kornelia Smalla 2, and Mika T. Tarkka 1,6,†, 1 Helmholtz Centre for Environmental Research, Theodor-Lieser-Str. 4, 06120 Halle, Germany 2 Julius Kühn-Institut, Messeweg 11/12, 38104, Braunschweig, Germany 3 Leibniz Institute of Plant Genetics and Crop Plant Research (IPK), Corrensstr. 3, 06466 Gatersleben, Germany 4 Copenhagen University, Universitetsparken 15, 2100, Copenhagen, Denmark 5 Martin Luther University Halle-Wittenberg, Von-Seckendorff-Platz 3, 06120 Halle, Germany 6 German Centre for Integrative Biodiversity Research (iDiv) Halle–Jena–Leipzig, Deutscher Platz 5E, 04103 Leipzig, Germany * Joint first authors. † Correspondence: mika.tarkka@ufz.de Received 7 April 2020; Editorial decision 14 May 2020; Accepted 25 May 2020 Editor: Miriam Gifford, University of Warwick, UK Abstract Non-invasive X-ray computed tomography (XRCT) is increasingly used in rhizosphere research to visualize development of soil–root interfaces in situ. However, exposing living systems to X-rays can potentially impact their processes and metabolites. In order to evaluate these effects, we assessed the responses of rhizosphere processes 1 and 24 h after a low X-ray exposure (0.81 Gy). Changes in root gene expression patterns occurred 1 h after exposure with down-regulation of cell wall-, lipid metabolism-, and cell stress-related genes, but no differences remained after 24 h. At either time point, XRCT did not affect either root antioxidative enzyme activities or the composition of the rhizosphere bacterial microbiome and microbial growth parameters. The potential activities of leucine aminopeptidase and phosphomonoesterase were lower at 1 h, but did not differ from the control 24 h after exposure. A time delay of 24 h after a low X-ray exposure (0.81 Gy) was sufficient to reverse any effects on the observed rhizosphere systems. Our data suggest that before implementing novel experimental designs involving XRCT, a study on its impact on the investigated processes should be conducted. Keywords: Bacterial community composition, extracellular soil enzyme, maize, plant elemental composition, rhizosphere, root gene expression, X-ray computed tomography. Introduction According to a recent report by the United Nations, the number of people suffering from hunger has been increasing over the past years, with climate variability and weather extremes being key contributing factors (FAO, 2018). To develop climate- resilient crops and microbiomes, there is an urgent need for a better understanding of plant–soil interactions. Root system Downloaded from https://academic.oup.com/jxb/article/71/18/5603/5848217 by guest on 28 June 2022