The ethylene-responsive transcription factor of durum wheat, TdSHN1, confers cadmium, copper, and zinc tolerance to yeast and transgenic tobacco plants.

Abstract

Cadmium (Cd), copper (Cu), and zinc (Zn) are among the most common heavy metals (HMs) present in polluted soils. While some HMs are required for key biological processes, they are toxic when present in excess. This toxicity damages plant health, decreases crop yields, and can impact human health via the food chain. For example, durum wheat is a staple food that is known to accumulate Cd when grown on polluted soils. Plant response to HM stress is complex and involves several transcription factors (TFs) among which members of the ERF family. Although roles of SHINE-type ERF transcription factors in abiotic stress tolerance have been thoroughly investigated, there is little information concerning their role in HM stress tolerance. In the present study, we investigated the role of durum wheat TdSHN1 TF in HM response and tolerance. Results showed that TdSHN1 expression was strongly induced by Cd, Cu, and Zn in durum wheat seedlings. In addition, TdSHN1 gene promoter directed HM-inducible GUS gene expression in transgenic tobacco. Overexpression of TdSHN1 encoding cDNA in transgenic yeast and tobacco conferred Cd, Cu, and Zn tolerances. Interestingly, transgenic tobacco lines exhibited longer roots and greater biomass accumulation, retained more chlorophyll, and produced less ROS than WT plants, when subjected to excess HMs. In addition, transgenic tobacco lines had higher activities of ROS-scavenging enzymes (SOD and CAT) which might have contributed to their HM tolerance. This study suggested that TdSHN1 is a potential candidate for improving HM tolerance in plants and phytoremediation of HM-contaminated soils.