Variation in cadmium accumulation and speciation within the same population of the hyperaccumulator Noccaea caerulescens grown in a moderately contaminated soil

Authors: YAN, JIALI - Nanjing Agricultural University; TANG, ZHONG - Nanjing Agricultural University; Fischel, Matthew; WANG, PENG - Nanjing Agricultural University; SIEBECKER, MATTHEW - University Of Delaware; AARTS, MARK - Wageningen University; SPARKS, DONALD - University Of Delaware; ZHAO, FANG-JIE - Nanjing Agricultural University

Submitted to: Plant and Soil
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/4/2022
Publication Date: 3/16/2022
Citation: Yan, J., Tang, Z., Fischel, M.H., Wang, P., Siebecker, M.G., Aarts, M.G., Sparks, D.L., Zhao, F. 2022. Variation in cadmium accumulation and speciation within the same population of the hyperaccumulator Noccaea caerulescens grown in a moderately contaminated soil. Plant and Soil. https://doi.org/10.1007/s11104-022-05373-w.
DOI: https://doi.org/10.1007/s11104-022-05373-w

Interpretive Summary: Cadmium is a pollutant that impacts human health because it accumulates in soils and is taken up by crops. Growing plants that amass high levels of cadmium in their leaves, like alpine pennycress, is one potential method of removing cadmium from soils. We cultivated 29 distinct populations of alpine pennycress in cadmium contaminated paddy soils and determined if selective breeding can improve the plant size and cadmium uptake. We also resolved the chemical species and distribution of cadmium in the plant leaves, which illustrates the mechanism these plants use to detoxify cadmium within their cells. Results showed critical advances in how selective breeding can improve the ability of alpine pennycress to remove cadmium from contaminated soils and plant mechanisms used to tolerate cadmium within leaves. This information aids scientists in understanding how to reduce cadmium levels in contaminated soils by improving the efficiency of cadmium uptake by alpine pennycress through selective breeding.

Technical Abstract: Phytoextraction is an eco-friendly approach for remediation of heavy metal contaminated soil. The aim is to screen Noccaea caerulescens lines with higher cadmium (Cd) phytoextraction efficiency and investigate differences in Cd species and distribution in the leaves of high and low Cd accumulating lines. Biomass production and Cd bioaccumulation capacities of 29 Noccaea caerulescens lines, generated through single-seed-descent from a Cd hyperaccumulating calamine population, were assessed in a pot experiment with a moderately Cd contaminated soil (2.1 mg Cd kg-'1). Synchrotron-based techniques were employed to identify and characterize Cd speciation and distribution in Noccaea caerulescens leaves. The largest biomass of Noccaea caerulescens reached 5.0'±'3.3 g (D. W. pot-'1) after 6 months growth. The Cd concentrations in shoots varied from 85 to 203 mg kg-'1. The most efficient line removed 0.64 mg Cd pot-'1 and lowered the total Cd in soil by 30%. Synchrotron-based X-ray absorption spectroscopy showed that the dominant Cd species was Cd-thiol complexes. Cadmium-carboxyl and Cd-phytate/phosphate were present in the leaves of high and low Cd accumulating lines, respectively. Micro X-ray fluorescence microscopy showed cadmium was concentrated in leaf veins. There are wide variations including both biomass production and Cd accumulation capacity among different lines within the same calamine ecotype of Noccaea caerulescens. Cadmium-thiol complexes play the most important role in Cd detoxification in leaves of Noccaea caerulescens grown in moderately Cd contaminated paddy soil. These findings provide a physiological basis for breeding high Cd accumulation varieties of Noccaea caerulescens.