Differentially expressed wheat genes in response to powdery mildew infection

Powdery mildew, caused by Blumeria graminis f. sp. tritici (Bgt), is an important foliar disease of wheat (Triticum aestivum) worldwide. The PmHNK gene confers a high level of resistance to several races of Bgt in the Henan Province, China. To identify differentially expressed transcripts during host-pathogen interaction, two bulks of F-3 plants contrasting in the presence of PmHNK derived from cross Zhoumai 22xZhoumai 19 were inoculated with a Bgt isolate 08B1. Wheat tissue from each bulk was collected at 24 and 48 h after inoculation and characterised for gene expression patterns during the R-gene-mediated compatible and incompatible interactions using the Affymetrix Wheat GeneChip. A total of 289 up-regulated and 154 down-regulated transcripts were identified in the incompatible interaction, and 218 up-regulated and 167 down-regulated transcripts were found in the compatible interaction. Among the differentially expressed transcripts, only 100 were unique for the incompatible interaction and 42 were unique for the compatible interaction. In addition, 34 PmHNK regulated and 15 Pmhnk regulated transcripts were constitutively expressed. Annotation of the induced transcripts revealed that the presence of PmHNK resulted in a resistance response involving salicylic acid and ethylene signalling pathways and defence-related transcripts, including hypersensitive response (HR) specific transcripts. These findings will provide new insights in understanding the molecular mechanisms underlining wheat resistance to powdery mildew.