IRT1 and ZIP2 were involved in exogenous hydrogen-rich water-reduced cadmium accumulation in Brassica chinensis and Arabidopsis thaliana

doi:10.1016/j.jhazmat.2020.124599

Journal of Hazardous Materials

Volume 407, 5 April 2021, 124599

https://doi.org/10.1016/j.jhazmat.2020.124599 Get rights and content

Highlights

•
NMT analyses revealed the positive role of HRW in reducing Cd uptake in pak choi.
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Apart from irt1 and zip1-mutant, Cd concentrations of all Arabidopsis thaliana were reduced by HRW.
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Ionic concentration and NMT analyses revealed that HRW enhanced the competition between Zn and Cd.

Abstract

The results of Cd (cadmium) concentration, Cd²⁺ fluorescent staining, NMT (non-invasive micro-test technology) analysis of Cd absorption revealed the remarkably positive role of HRW in reducing Cd uptake by root of pak choi seedlings. BcIRT1 (iron-regulated transporter 1) and BcZIP2 (zinc-regulated transporter protein 2) are the main Cd transporters in pak choi, but their roles in the process of HRW-reduced Cd uptake is still far from being answered. In this study, we specifically verified the function of IRT1 and ZIP2 in HRW-reduced Cd absorption in pak choi and Arabidopsis thaliana. Heterologous and homologous expression in Arabidopsis thaliana displayed that Cd concentrations in wild-type (Col-0) and transgenic A. thaliana of IRT1 and ZIP2 were significantly reduced by HRW, except for irt1- and zip2-mutant. NMT detection showed that HRW not only decreased Cd²⁺ influx in root of WT and transgenic lines, but also enhanced the competition between Zn and Cd. Taken together, the HRW-induced reduction of Cd accumulation in plants may be result from depressing the expression of BcIRT1 and BcZIP2 and affecting the preference of BcIRT1 and BcZIP2 in ion uptake.

Graphical Abstract

Introduction

Cadmium (Cd) is identified as one of the most toxic contaminants in soil because of its severe toxicity, non-biodegradability and high-water solubility (Fan et al., 2019). Cd can be absorbed by plants, as it has a highly similarity to some nutritive elements in chemical properties, and finally it enters into human body by food chain. In plants, lipid peroxidation, destruction of cell membranes and suppression of enzyme activities are the usual damages caused by Cd (Hassan et al., 2016, DalCorso et al., 2010, Andresen and Kupper, 2013). Moreover, the accumulation and uptake of mineral nutrients in plants could be remarkably influenced by Cd stress (Lopez-Millan et al., 2009, Zhi et al., 2015, Li et al., 2016). Pak choi (Brassica chinensis) is cultivated world-widely and has a high ability to accumulate Cd in its edible parts (Zhou et al., 2016, Sun et al., 2010). It has serious potential health risks for humans to consume pak choi that grown in Cd-contaminated soil (Yan et al., 2009, Chen et al., 2012, Gill and Tuteja, 2010). Hence, the exploration of effective measures to decrease the Cd accumulation in pak choi is indispensable.

Cd moves into plants as a hitchhiker through transporters for other essential and beneficial elements. AtIRT1 (iron-regulated transporter 1) is the major transporter for Fe (iron) uptake from the soil (Vert et al., 2002) and has capacity for transportation of several divalent metals like Fe, Zn (Zinc), Mn (manganese) and Cd (Rogers et al., 2000). Our previous research also found that BcIRT1 could transport Fe, Zn, Mn and Cd (Wu et al., 2019). Meanwhile, ZIP (zinc-regulated transporter protein) family can encode plasma membrane Zn transporters in rice, like ZIP1 and ZIP8 (Ishimaru et al., 2007, Lee et al., 2010a, Lee et al., 2010b, Ramesh et al., 2003, Yang et al., 2009). ZIP gene family can transport many metal elements such as Cd, Fe, Zn and Mn (Guerinot, 2000, Milner et al., 2013), and we found that BcZIP2 can transport Fe, Zn, Mn and Cd in our previous study (Wu et al., 2019). Many studies have shown that inhibited-expression of IRTs and ZIPs can significantly decrease the concentrations of Cd in plants (Zhu et al., 2012, Zeng et al., 2017).

Nowadays, it has shown that application of multitudinous substances is an effective and convenient measure to reduce the uptake, translocation and accumulation of Cd in plants including Fe fertilization, gadolinium, N-Acetylcysteine, glutathione, hemin and so forth (Chen et al., 2017, Han et al., 2019, Colak et al., 2019, Huang et al., 2019, Zhu et al., 2019). Hydrogen gas (H₂) is a kind of colorless, odorless and tasteless gas on the earth (Huang et al., 2010). According to some previous studies, H₂ serves as an antioxidative, anti-apoptotic and anti-inflammatory substance in animals (Huang et al., 2010, Zheng et al., 2011). Furthermore, H₂ as a form of hydrogen-rich water (HRW) has capacity for resisting abiotic stresses in plants. For Cd stress, HRW improved resistance of alfalfa and pak choi by increasing the antioxidative activities and repressing the absorption of Cd (Cui et al., 2013, Wu et al., 2015, Wu et al., 2020). HRW recovered Medicago sativa from Cd toxicity by elevating sulfur compound metabolic processes, decreasing oxidative stress and sustaining the homeostasis of nutrient elements (Chen et al., 2017). In our previous study, HRW significantly alleviated the Cd damages to pak choi seedlings and suppressed the Cd accumulation in roots and shoots (Wu et al., 2019). Based on our previous analysis of RNA-seq, the expressions of BcIRT1 and BcZIP2 were inhibited by HRW which may result in the inhibition of Cd uptake in pak choi seedlings (Wu et al., 2019). However, no definite evidences have been figured out on the role of BcIRT1 and BcZIP2 in decreasing Cd accumulation by HRW in pak choi, to date.

In this research, the inhibition of net Cd²⁺ flux in pak choi root by HRW was directly performed by NMT (non-invasive micro-test technology) analyses and the effect of HRW on the Cd uptake of pak choi was constructed by detecting ion concentration in seedlings. What’s more, the influence of HRW on the Fe and Zn under Cd treatment in pak choi and transgenic Arabidopsis thaliana was expounded by the ionic concentration and NMT analyses. To sum up, a further verification was given to perform the positive role of BcIRT1 and BcZIP2 in suppressing Cd accumulation by HRW in this research.

Section snippets

Plant materials and growth conditions

Seeds of pak choi (Brassica chinensis, Dongfang 2) were soaked in deionized water at 25 ℃ for 3–5 h and then germinated at 25 ℃ all night. Uniform-sized seeds were cultivated in 1/4 Hoagland’s solution at 23–25 ℃ with 16/8 h light/dark cycle in an illuminated incubator until the seedlings grown to two true leaves and a terminal bud. The nutrient solutions were prepared with 0 or without HRW (50% saturation). After 1 d, seedlings were transferred into solutions containing 0, 50% HRW and 1, 5 or

HRW alleviated the growth inhibition caused by 50 μM Cd stress in pak choi

The root length of pak choi was reduced by approximately 27.5% with 50 μM Cd treatment, which was significantly recovered by HRW addition with 17.14% (Fig. 1A and B). The root fresh weight was sharply reduced by approximately 60.02% with 50 μM Cd treatment, and significantly relieved by HRW with 32.36% (Fig. 1C). While, 1 and 5 μM Cd treatment didn’t affect the growth of pak choi and HRW could not perform the function in the alleviation of Cd stress. (Fig. S1A and B).

HRW decreased Cd uptake and equilibrated the ionic disorder caused by Cd in pak choi

As shown in Fig. 2, the

Discussion

The cadmium contamination in vegetable is considered as an urgent issue to address. Some exogenous agents were found having the ability to significantly decrease the Cd accumulation in the edible parts of pak choi (Huang et al., 2010, Huang et al., 2019, Zhu et al., 2019). Thereinto, HRW has been proved many times in pak choi (Wu et al., 2015, Wu et al., 2019). Moreover, it has been reported that HRW is capable for relieving other heavy metal stress to plants (Cui et al., 2013, Wu et al., 2015,

Conclusion

Our study provides new insights into the molecular mechanism underlying the effect of HRW on reducing Cd accumulation in pak choi. HRW had the capacity for reducing the transcriptional levels of BcIRT1 and BcZIP2 involved in Cd uptake. In addition, HRW could affect the Fe and Zn accumulation in pak choi and Arabidopsis thaliana under Cd exposure and altered the competitiveness between Zn and Cd. Although it is indefinite which way is directly adopted by HRW to regulate BcIRT1 and BcZIP2, our

CRediT authorship contribution statement

Xue Wu and Nana Su: extracted, analyzed the data and wrote the first draft. Xiaomeng Yue and Bo Fang: developed illustration in the paper. Jianwen Zou and Yahua Chen: revised the paper. Zhenguo Shen and Jin Cui: conceived and designed the paper.

Acknowledgments

This study was supported by China Agriculture Research System (CARS-23-A03) and The National Key Research and Development Program of China (2016YFD0800700-3).

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

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¹: These authors contributed equally to this work.

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Research PaperIRT1 and ZIP2 were involved in exogenous hydrogen-rich water-reduced cadmium accumulation in Brassica chinensis and Arabidopsis thaliana

Highlights

Abstract

Graphical Abstract

Introduction

Section snippets

Plant materials and growth conditions

HRW alleviated the growth inhibition caused by 50 μM Cd stress in pak choi

HRW decreased Cd uptake and equilibrated the ionic disorder caused by Cd in pak choi

Discussion

Conclusion

CRediT authorship contribution statement

Acknowledgments

Declaration of Competing Interest

Ecotoxicol. Environ. Saf.

Ecotoxicol. Environ. Saf.

J. Hazard. Mater.

Plant Physiol. Biochem.

BBA

Ecotoxicol. Environ. Saf.

Mol. Cells

Plant Physiol. Biochem.

Food Chem.

Environ. Exp. Bot.

Plant Sci.

Environ. Pollut.

J. Plant Physiol.

Chemosphere

Ecotoxicol. Environ. Saf.

Ecotoxicol. Environ. Saf.

J. Environ. Sci. China

J. Hazard. Mater.

Ecotoxicol. Environ. Saf.

Cadmium toxicity in plants

Met. Ions Life Sci.

Nitric oxide contributes to cadmium toxicity in arabidopsis by promoting cadmium accumulation in roots and by up-regulating genes related to iron uptake

Plant Physiol.

Accumulation and translocationof Cd metal and the Cd-induced production of glutathione and phytochelatins in Vicia faba L

Acta Physiol. Plant

Proteomic analysis provides insights into the molecular bases of hydrogen gas-induced cadmium resistance in Medicago sativa

J. Proteom.

Research Paper
IRT1 and ZIP2 were involved in exogenous hydrogen-rich water-reduced cadmium accumulation in Brassica chinensis and Arabidopsis thaliana