Molecular Responses to Cadmium Exposure in Two Contrasting Durum Wheat Genotypes

Erika Sabella,Luigi De Bellis,Alessandra Genga,Andrea Luvisi,Alessio Aprile

doi:10.3390/ijms22147343

Erika Sabella, Luigi De Bellis + Show 3 more

Open Access

https://doi.org/10.3390/ijms22147343

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Abstract

Cadmium is a heavy metal that can be easily accumulated in durum wheat kernels and enter the human food chain. Two near-isogenic lines (NILs) with contrasting cadmium accumulation in grains, High-Cd or Low-Cd (H-Cd NIL and L-Cd NIL, respectively), were used to understand the Cd accumulation and transport mechanisms in durum wheat roots. Plants were cultivated in hydroponic solution, and cadmium concentrations in roots, shoots and grains were quantified. To evaluate the molecular mechanism activated in the two NILs, the transcriptomes of roots were analyzed. The observed response is complex and involves many genes and molecular mechanisms. We found that the gene sequences of two basic helix–loop–helix (bHLH) transcription factors (bHLH29 and bHLH38) differ between the two genotypes. In addition, the transporter Heavy Metal Tolerance 1 (HMT-1) is expressed only in the low-Cd genotype and many peroxidase genes are up-regulated only in the L-Cd NIL, suggesting ROS scavenging and root lignification as active responses to cadmium presence. Finally, we hypothesize that some aquaporins could enhance the Cd translocation from roots to shoots. The response to cadmium in durum wheat is therefore extremely complex and involves transcription factors, chelators, heavy metal transporters, peroxidases and aquaporins. All these new findings could help to elucidate the cadmium tolerance in wheat and address future breeding programs.

Highlights

Plants promptly take up Cd from soil since it has a high solubility in water and, even at low concentrations, it can cause phytotoxic effects
We found three contigs upregulated both in the L-Cd and H-Cd near-isogenic lines (NILs); they are annotated as basic helix–loop–helix (bHLH) transcription factors
NILs which could be involved in Cd compartmentalization at the root level

Summary

Introduction

Heavy metals naturally occur in the soil as rare elements; their amounts are increasing due to human activities which continuously aggravate environmental pollution. Cadmium (Cd) is one of the most toxic, both for human health and for plants [1,2]. Plants promptly take up Cd from soil since it has a high solubility in water and, even at low concentrations, it can cause phytotoxic effects Other examples of phytotoxic effects are the decrease in photosynthesis rate, transpiration rate, stomatal conductance, etc.) [4,5]. The mechanisms of Cd biotoxicity are the result of multiple biological effects on membranes, on mitochondrial structure and function, on DNA and on gene expression

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