A hidden demethylation pathway removes mercury from rice plants and mitigates mercury flux to food chains

Tang W 1 , Bai X 2 , Zhou Y 1 , Sonne C 3 , Wu M 1 , Lam SS 4 Show all authors , Hintelmann H 5 , Mitchell CPJ 6 , Johs A 7 , Gu B 7 , Nunes L 8 , Liu C 9 , Feng N 10 , Yang S 11 , Rinklebe J 12 , Lin Y 13 , Chen L 14 , Zhang Y 15 , Yang Y 1 , Wang J 1 , Li S 1 , Wu Q 16 , Ok YS 17 , Xu D 2 , Li H 2 , Zhang XX 1 , Ren H 1 , Jiang G 18 , Chai Z 2 , Gao Y 19 , Zhao J 20 , Zhong H 21

Affiliations 

  • 1 School of the Environment, Nanjing University, State Key Laboratory of Pollution Control and Resource Reuse, Nanjing, China
  • 2 Key Laboratory for Biomedical Effects of Nanomaterials and Nanosafety, Institute of High Energy Physics (IHEP), Chinese Academy of Sciences (CAS), Beijing, China
  • 3 Department of Ecoscience, Arctic Research Centre, Aarhus University, Roskilde, Denmark. cs@ecos.au.dk
  • 4 Higher Institution Centre of Excellence (HICoE), Institute of Tropical Aquaculture and Fisheries (AKUATROP), Universiti Malaysia Terengganu, Kuala Nerus, Malaysia
  • 5 Department of Chemistry and School of the Environment, Trent University, Peterborough, Ontario, Canada
  • 6 Department of Physical and Environmental Sciences, University of Toronto Scarborough, Scarborough, Ontario, Canada
  • 7 Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA
  • 8 Faculty of Sciences and Technology, Civil Engineering Research and Innovation for Sustainability Center, University of Algarve, Faro, Portugal
  • 9 Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, China
  • 10 College of Life Science and Technology, Jinan University, Guangzhou, China
  • 11 State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Nanjing University, Nanjing, China
  • 12 School of Architecture and Civil Engineering, Institute of Foundation Engineering, Water and Waste Management, Laboratory of Soil and Groundwater Management, University of Wuppertal, Wuppertal, Germany
  • 13 Tianjin Key Laboratory of Environmental Technology for Complex Trans-Media Pollution, College of Environmental Science and Engineering, Nankai University, Tianjin, China
  • 14 Key Laboratory of Geographic Information Science (Ministry of Education), School of Geographic Sciences, East China Normal University, Shanghai, China
  • 15 School of Atmospheric Sciences, Nanjing University, Nanjing, China
  • 16 State Key Joint Laboratory of Environmental Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing, China
  • 17 Korea Biochar Research Center, APRU Sustainable Waste Management Program and Division of Environmental Science and Ecological Engineering, Korea University, Seoul, Republic of Korea
  • 18 State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, China
  • 19 Key Laboratory for Biomedical Effects of Nanomaterials and Nanosafety, Institute of High Energy Physics (IHEP), Chinese Academy of Sciences (CAS), Beijing, China. gaoyx@ihep.ac.cn
  • 20 Key Laboratory for Biomedical Effects of Nanomaterials and Nanosafety, Institute of High Energy Physics (IHEP), Chinese Academy of Sciences (CAS), Beijing, China. zhaojt@zju.edu.cn
  • 21 School of the Environment, Nanjing University, State Key Laboratory of Pollution Control and Resource Reuse, Nanjing, China. zhonghuan@nju.edu.cn
Nat Food, 2024 Jan;5(1):72-82.
PMID: 38177223 DOI: 10.1038/s43016-023-00910-x

Abstract

Dietary exposure to methylmercury (MeHg) causes irreversible damage to human cognition and is mitigated by photolysis and microbial demethylation of MeHg. Rice (Oryza sativa L.) has been identified as a major dietary source of MeHg. However, it remains unknown what drives the process within plants for MeHg to make its way from soils to rice and the subsequent human dietary exposure to Hg. Here we report a hidden pathway of MeHg demethylation independent of light and microorganisms in rice plants. This natural pathway is driven by reactive oxygen species generated in vivo, rapidly transforming MeHg to inorganic Hg and then eliminating Hg from plants as gaseous Hg°. MeHg concentrations in rice grains would increase by 2.4- to 4.7-fold without this pathway, which equates to intelligence quotient losses of 0.01-0.51 points per newborn in major rice-consuming countries, corresponding to annual economic losses of US$30.7-84.2 billion globally. This discovered pathway effectively removes Hg from human food webs, playing an important role in exposure mitigation and global Hg cycling.

* Title and MeSH Headings from MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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