Zinc alleviates cadmium toxicity by modulating photosynthesis, ROS homeostasis, and cation flux kinetics in rice

Muhammad Faheem Adil; Shafaque Sehar; Zhigang Han; Jonas Lwalaba Wa Lwalaba; Ghulam Jilani; Fanrong Zeng; Zhong-Hua Chen; Imran Haider Shamsi

doi:10.1016/j.envpol.2020.114979

Zinc alleviates cadmium toxicity by modulating photosynthesis, ROS homeostasis, and cation flux kinetics in rice

Environ Pollut. 2020 Oct;265(Pt B):114979. doi: 10.1016/j.envpol.2020.114979. Epub 2020 Jun 15.

Authors

Muhammad Faheem Adil¹, Shafaque Sehar¹, Zhigang Han¹, Jonas Lwalaba Wa Lwalaba¹, Ghulam Jilani², Fanrong Zeng¹, Zhong-Hua Chen³, Imran Haider Shamsi⁴

Affiliations

¹ Department of Agronomy, College of Agriculture and Biotechnology, Key Laboratory of Crop Germplasm Resource, Zhejiang University, Hangzhou, 310058, People's Republic of China.
² Institute of Soil Science, PMAS Arid Agriculture University, Rawalpindi, 46300, Pakistan.
³ School of Science, Western Sydney University, Penrith, NSW, 2751, Australia; Hawkesbury Institute for the Environment, Western Sydney University, Penrith, NSW, 2751, Australia.
⁴ Department of Agronomy, College of Agriculture and Biotechnology, Key Laboratory of Crop Germplasm Resource, Zhejiang University, Hangzhou, 310058, People's Republic of China. Electronic address: drimran@zju.edu.cn.

PMID: 32585549
DOI: 10.1016/j.envpol.2020.114979

Abstract

Understanding of cadmium (Cd) uptake mechanism and development of lower Cd crop genotypes are crucial for combating its phytotoxicity and meeting 70% increase in food demand by 2050. Bio-accumulation of Cd continuously challenges quality of life specifically in regions without adequate environmental planning. Here, we investigated the mechanisms operating in Cd tolerance of two rice genotypes (Heizhan-43 and Yinni-801). Damage to chlorophyll contents and PSII, histochemical staining and quantification of reactive oxygen species (ROS), cell viability and osmolyte accumulation were studied to decipher the interactions between Cd and zinc (Zn) by applying two Cd and two Zn levels (alone as well as combined). Cd²⁺ and Ca²⁺ fluxes were also measured by employing sole Cd₁₀₀ (100 μmol L^-1) and Zn₅₀ (50 μmol L^-1), and their combination with microelectrode ion flux estimation (MIFE) technique. Cd toxicity substantially reduced chlorophyll contents and maximal photochemical efficiency (F_v/F_m) compared to control plants. Zn supplementation reverted the Cd-induced toxicity by augmenting osmoprotectants and interfering with ROS homeostasis under combined treatments, particularly in Yinni-801 genotype. Fluorescence microscopy indicated a unique pattern of live and dead root cells, depicting more damage with Cd₁₀, Cd₁₅ and Cd₁₅+Zn₅₀. Our results confer that Cd²⁺ impairs the uptake of Ca²⁺ whereas, Zn not only competes with Cd²⁺ but also Ca²⁺, thereby modifying ion homeostasis in rice plants. This study suggests that exogenous application of Zn is beneficial for rice plants in ameliorating Cd toxicity in a genotype and dose dependent manner by minimizing ROS generation and suppressing collective oxidative damage. The observations confer that Yinni-801 performed better than Heizhan-43 genotype mainly under combined Zn treatments with low-Cd, presenting Zn fortification as a solution to increase rice production.

Keywords: Cd influx; Cell viability; Chlorophyll contents; Microelectrode ion flux measurement; Oryza sativa L.; Osmoprotectants.

MeSH terms

Cadmium
Cations
Homeostasis
Kinetics
Oryza*
Photosynthesis*
Quality of Life
Reactive Oxygen Species
Zinc

Substances

Cations
Reactive Oxygen Species
Cadmium
Zinc