The WRKY transcription factor RsWRKY28 mediates cadmium extrusion via activating RsPDR8 expression in radish (Raphanus sativus L.).

Cadmium (Cd) is a widespread dangerous pollutant for its toxic effects on plants and human beings. The uptake and accumulation of Cd from soil impedes taproot enlargement, thereby reducing yield, quality and safety of radish taproot. However, the molecular mechanisms and regulatory networks underlying Cd accumulation in radish remain unclear. Here, we found that the Cd content in radish root of overexpressing RsPDR8 was significantly reduced compared with the control and the expression of RsPDR8 was positively regulated by RsWRKY28. Overexpression of RsWRKY28 promoted RsPDR8 expression and conferred Cd tolerance, while suppression of RsWRKY28 led to increased Cd accumulation and sensitivity of radish to Cd stress. Additionally, phosphorylation of RsWRKY28 by RsMAPK6 further enhanced its transcriptional regulation of RsPDR8, thereby further reducing Cd accumulation. The outcomes of this study indicates that RsWRKY28-RsPDR8 module is important in reducing Cd accumulation in radish, which would facilitate genetically developing elite low-Cd-content cultivars in radish breeding programs.