Nitrogen fertilizer affects rhizosphere Cd re-mobilization by mediating gene AmALM2 and AmALMT7 expression in edible amaranth roots

Zhi-Min Xu; Jun-Feng Wang; Wan-Li Li; Yi-Fan Wang; Tao He; Fo-Peng Wang; Zi-Yan Lu; Qu-Sheng Li

doi:10.1016/j.jhazmat.2021.126310

Nitrogen fertilizer affects rhizosphere Cd re-mobilization by mediating gene AmALM2 and AmALMT7 expression in edible amaranth roots

J Hazard Mater. 2021 Sep 15:418:126310. doi: 10.1016/j.jhazmat.2021.126310. Epub 2021 Jun 6.

Authors

Zhi-Min Xu¹, Jun-Feng Wang², Wan-Li Li², Yi-Fan Wang³, Tao He², Fo-Peng Wang², Zi-Yan Lu⁴, Qu-Sheng Li⁵

Affiliations

¹ Key Laboratory of Environmental Pollution and Health of Guangdong Province, School of Environment, Jinan University, Guangzhou 510632, China; Engineering and Technology Research Center for Agricultural Land Pollution Prevention and Control of Guangdong Higher Education Institutes, College of Resources and Environment, Zhongkai University of Agriculture and Engineering, Guangzhou 510225, China.
² Key Laboratory of Environmental Pollution and Health of Guangdong Province, School of Environment, Jinan University, Guangzhou 510632, China.
³ Key Laboratory of Environmental Pollution and Health of Guangdong Province, School of Environment, Jinan University, Guangzhou 510632, China; Department of Biotechnology, The University of Tokyo, Tokyo 113-8657, Japan.
⁴ Engineering and Technology Research Center for Agricultural Land Pollution Prevention and Control of Guangdong Higher Education Institutes, College of Resources and Environment, Zhongkai University of Agriculture and Engineering, Guangzhou 510225, China.
⁵ Key Laboratory of Environmental Pollution and Health of Guangdong Province, School of Environment, Jinan University, Guangzhou 510632, China. Electronic address: liqusheng@21cn.com.

PMID: 34130167
DOI: 10.1016/j.jhazmat.2021.126310

Abstract

In-situ stabilization of Cd-contaminated farmland is a commonly used remediation technology. Yet, rhizosphere metabolites (e.g., organic acids) during crop cultivation may cause Cd re-mobilization and over-accumulation. Here, we identified four pivotal cytomembrane-localized genes underlying Cd accumulation difference between two contrasting edible amaranth cultivars based on root gene expression profile, studied their subcellular localization and functional characteristics, and then investigated effects of nitrogen fertilizer on their expression and rhizosphere Cd re-mobilization. Results showed that more Cd accumulated by edible amaranth was due to rhizosphere Cd mobilization by mediating high expression of AmALMT2 and AmALMT7 genes, not Cd transporters in roots. This was confirmed by heterologous expression of AmALMT2 and AmALMT7 genes in Arabidopsis thaliana, since they mediated malic, fumaric, succinic, and aspartic acids efflux. Furthermore, nitrogen influencing rhizosphere acidification might be closely associated with organic acids efflux genes. Compared with N-NO₃^- application, N-NH₄⁺ was massively assimilated into glutamates and oxaloacetates through up-regulating glutamine synthetase and alanine-aspartate-glutamate metabolic pathways, thereby enhancing TCA cycle and organic acids efflux dominated by binary carboxylic acids via up-regulating AmALMT2 and AmALMT7 genes, which finally caused Cd re-mobilization. Therefore, N-NO₃^--dominated nitrogen retarded rhizosphere Cd re-mobilization via inhibiting organic acids efflux function of AmALMT2 and AmALMT7 proteins.

Keywords: AmALMT2 and AmALMT7 genes; Nitrogen assimilation; Organic acid effluxes; Rhizosphere acidification; Soil Cd re-mobilization.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Cadmium / analysis
Fertilizers
Nitrogen
Plant Roots / chemistry
Rhizosphere*
Soil
Soil Pollutants* / analysis

Substances

Fertilizers
Soil
Soil Pollutants
Cadmium
Nitrogen