RsWRKY15-RsPDR12 module regulates Cd uptake and accumulation by promoting Cd efflux in radish (Raphanus sativus L.).

Abstract

Cadmium (Cd), a non-essential and toxic heavy metal, accumulates in radish taproot and adversely affects radish safety and quality. Pleiotropic drug resistance (PDR) proteins play a crucial role in heavy metal uptake and accumulation in plants. However, the PDR gene-mediated regulation of Cd accumulation remains unexplored in radish. RsPDR12 gene expression significantly increased under Cd stress. RsPDR12 demonstrated Cd transport activity and decreased Cd accumulation in yeast cells, and its overexpression reduced root Cd concentration by Cd²⁺ efflux in Arabidopsis. RsPDR12 alleviated Cd stress by enhancing membrane permeability and reactive oxygen species (ROS) scavenging in radish plants. RsWRKY15 was identified as the upstream regulatory factor of RsPDR12. Dual-luciferase assay demonstrated that RsWRKY15 bound to the RsPDR12 promoter to activate its transcription. RsWRKY15 expression and promoter activity were significantly induced under Cd stress. RsWRKY15 overexpression mitigated oxidative damage and reduced root Cd concentration in radish and Nicotiana benthamiana plants, respectively. These findings advance understanding of the molecular mechanism underlying the RsWRKY15-RsPDR12 mediated regulatory network of Cd accumulation and support the genetic improvement of low Cd-accumulation cultivars in radish breeding programs.