AbstractBackgroundThe degradation of intracellular proteins plays an essential role in plant responses to stressful environments. ClpS1 and E3 ubiquitin ligase function as adaptors for selecting target substrates in caseinolytic peptidase (Clp) proteases pathways and the 26S proteasome system, respectively. Currently, the role of E3 ubiquitin ligase in the plant immune response to pathogens is well defined. However, the role of ClpS1 in the plant immune response to pathogens remains unknown.ResultsHere, wheat (Triticum aestivum) ClpS1 (TaClpS1) was studied and resulted to encode 161 amino acids, containing a conserved ClpS domain and a chloroplast transit peptide (1–32 aa). TaClpS1 was found to be specifically localized in the chloroplast when expressed transiently in wheat protoplasts. The transcript level ofTaClpS1in wheat was significantly induced during infection byPuccinia striiformisf. sp.tritici(Pst). Knockdown ofTaClpS1via virus-induced gene silencing (VIGS) resulted in an increase in wheat resistance againstPst, accompanied by an increase in the hypersensitive response (HR), accumulation of reactive oxygen species (ROS) and expression ofTaPR1andTaPR2, and a reduction in the number of haustoria, length of infection hypha and infection area ofPst. Furthermore, heterologous expression ofTaClpS1inNicotiana benthamianaenhanced the infection byPhytophthora parasitica.ConclusionsThese results suggest that TaClpS1 negatively regulates the resistance of wheat toPst.