Bna.GSH1 mediate the ABA signal to promote the tolerance of cadmium in Brassica napus L.

The presence of heavy metal pollution endangers human health substantially and severely damages agricultural productivity. A phytohormone, abscisic acid (ABA), might be beneficial for phytoremediation as it can boost the uptake of heavy metals and plant tolerance to harmful levels. Nevertheless, the mechanisms by which ABA signal regulation underlies cadmium (Cd) tolerance remain hitherto obscure. In this study, a molecular cascade regulating Cd tolerance in rapeseed was elucidated by overexpression of Bna.GSH1 enhanced Cd tolerance. This was associated with increased activities of superoxide dismutase (SOD), ascorbate peroxidase (APX), glutathione reductase (GR) and glutathione-S-transferase (GST), facilitating reactive oxygen species (ROS) scavenging. Moreover, the activation of phytochelatin synthase (PCS) caused an increase in phytochelatin (PC) accumulation, which lessened the toxicity of free Cd ions. Gene expression analysis revealed that ABA treatment restored the transcription level of Bna.GSH1 , Bna.ABF2 , Bna.ABF3 and Bna.ABI5 under Cd strss. It was demonstrated by molecular interaction studies that the transcription factors Bna.ABF2, Bna.ABF3 and Bna.ABI5 are directly binding to Bna.GSH1 promoter, and led to the activation of transcription. These findings provide critical insight into a novel ABA-Bna.ABF2/Bna.ABF3/Bna.ABI5- Bna.GSH1 module responsible for Cd tolerance in rapeseed and provides a valuable candidate locus for breeding Cd-resistant crop varieties.