Wheat Class III Peroxidase TaPOD70 Is a Potential Susceptibility Factor Negatively Regulating Wheat Resistance to Blumeria graminis f. sp. tritici

Powdery mildew, caused by Blumeria graminis f. sp. tritici (Bgt), is one of the most important diseases on wheat worldwide and can lead to a large reduction in wheat production. Class III peroxidases (PODs), a kind of secretory enzyme and members of a multigene family in higher plants, have been linked to various plant physiological functions and defensive responses. However, the role of PODs in wheat resistance to Bgt remains unclear. TaPOD70, a class III POD gene, was identified from the proteomics sequencing of the incompatible interaction between wheat (Triticum aestivum) cultivar Xingmin 318 and Bgt isolate E09. After transient expression of the TaPOD70-GFP fusion protein in Nicotiana benthamiana leaves, TaPOD70 was located in the membrane region. Yeast secretion assay showed that TaPOD70 was a secretory protein. Furthermore, Bax-induced programmed cell death was inhibited by transient expression of TaPOD70 in N. benthamiana. The transcript expression level of TaPOD70 was significantly upregulated in the wheat-Bgt compatible interaction. More crucially, knocking down TaPOD70 using virus-induced gene silencing increased wheat resistance to Bgt compared with the control plants. In response to Bgt, histological analyses indicated that hyphal development of Bgt was significantly reduced, whereas H2O2 production was enhanced in TaPOD70-silenced leaves. These findings imply that TaPOD70 may act as a susceptibility factor, adversely regulating wheat resistance to Bgt.