Metabolomic Profiles of the Creeping Wood Sorrel Oxalis corniculata in Radioactively Contaminated Fields in Fukushima: Dose-Dependent Changes in Key Metabolites.

Ko Sakauchi,Wataru Taira,Joji M Otaki

doi:10.3390/life12010115

Abstract

The biological impacts of the Fukushima nuclear accident, in 2011, on wildlife have been studied in many organisms, including the pale grass blue butterfly and its host plant, the creeping wood sorrel Oxalis corniculata. Here, we performed an LC–MS-based metabolomic analysis on leaves of this plant collected in 2018 from radioactively contaminated and control localities in Fukushima, Miyagi, and Niigata prefectures, Japan. Using 7967 peaks detected by LC–MS analysis, clustering analyses showed that nine Fukushima samples and one Miyagi sample were clustered together, irrespective of radiation dose, while two Fukushima (Iitate) and two Niigata samples were not in this cluster. However, 93 peaks were significantly different (FDR < 0.05) among the three dose-dependent groups based on background, low, and high radiation dose rates. Among them, seven upregulated and 15 downregulated peaks had single annotations, and their peak intensity values were positively and negatively correlated with ground radiation dose rates, respectively. Upregulated peaks were annotated as kudinoside D (saponin), andrachcinidine (alkaloid), pyridoxal phosphate (stress-related activated vitamin B6), and four microbe-related bioactive compounds, including antibiotics. Additionally, two peaks were singularly annotated and significantly upregulated (K1R1H1; peptide) or downregulated (DHAP(10:0); decanoyl dihydroxyacetone phosphate) most at the low dose rates. Therefore, this plant likely responded to radioactive pollution in Fukushima by upregulating and downregulating key metabolites. Furthermore, plant-associated endophytic microbes may also have responded to pollution, suggesting their contributions to the stress response of the plant.

Highlights

Environmental pollution caused by human activities is widespread around the globe in the 21st century
In the LC–MS analysis, 9554 peaks were detected, and 7967 peaks from 14 leaf samples were treated as valid peaks by MetaboAnalyst; 1587 peaks were treated as invalid because they showed a constant value across all samples or because they were detected only in one sample
To understand how these 14 samples from different localities responded to radiation, they were categorized into three groups depending on the ground radiation dose (Table 1)

Summary

Introduction

Environmental pollution caused by human activities is widespread around the globe in the 21st century. Recent human history has seen a series of pollution incidents by anthropogenic radionuclides: atomic bombs used in Hiroshima and Nagasaki, Japan (1945); atomic and hydrogen bomb experiments in Bikini Atoll (1946–1958); the Three Mile Island accident in the USA (1979); the Chernobyl nuclear accident in the Ukraine (1986); and the Fukushima nuclear accident, Japan (2011) [1]. The Fukushima nuclear accident in 2011 was the second largest nuclear accident next to the Chernobyl nuclear accident in 1986. One of the most serious environmental pollutants in this century is a group of radioactive materials released from nuclear bombs and the collapse of nuclear power plants. Anthropogenic 137Cs is detected from soil worldwide [2,3,4,5]

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Discussion

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