Wheat WD40-repeat protein TaHOS15 functions in a histone deacetylase complex to fine-tune defense response to Blumeriagraminis f.sp. tritici.

Powdery mildew caused by Blumeriagraminis f.sp. tritici (Bgt) seriously threatens the production of common wheat (Triticumaestivum L.). In eukaryotes, WD40-repeat (WDR) proteins usually participate in assembling protein complexes involved in a wide range of cellular processes. However, the potential function of WDR proteins in regulating crop resistance against biotrophic fungal pathogens, such as Bgt, remains unclear. In this study, we isolated TaHOS15, encoding a WDR protein, from wheat cultivar Jing411 and demonstrated that knockdown of TaHOS15 expression using virus- or transient-induced gene silencing attenuated wheat susceptibility to Bgt. The biochemical and molecular-biological assays revealed that TaHOS15 interacts with TaHDA6, a wheat homolog of Arabidopsis histone deacetylase AtHDA6, to constitute a transcriptional repressor complex. Furthermore, we defined the role of TaHOS15, which might act as an adaptor protein recruiting TaHDA6 to the chromatin of wheat defense-related genes including TaPR1, TaPR2, TaPR5, and TaWRKY45, where they repress histone acetylation. Moreover, reduced TaHOS15 or TaHDA6 transcript levels led to the decreased susceptibility to Bgt accompanied with the enhanced defense-related transcription under Bgt infection. Collectively, these results reveal that TaHOS15 functions in a histone deacetylase complex with TaHDA6 to fine-tune the defense response to Bgt in common wheat.