Genome-wide transcript profiling of barley rar3 in response to powdery mildew

Genes encoding early signaling events in pathogen defense often are identified only by their phenotype.  Such genes involved in barley-powdery mildew interactions include Mla, specifying race-specific resistance; Rar1 (Required for Mla12-specified resistance1), and Rom1 (Restoration of Mla-specified resistance1).  The RAR1-SGT1-HSP90 complex appears to function as chaperone in MLA-specified resistance, however, much remains to be discovered regarding the precise mechanisms of plant immunity.  Genetic analyses of fast-neutron mutants derived from CI 16151 (Mla6) uncovered a novel locus, designated Rar3 (Required for Mla6-specified resistance3).  Rar3 is independent of Mla6 and Rar1, and rar3 mutants are susceptible to Blumeria graminis f. sp. hordei (Bgh) isolate 5874 (AVR_a6), whereas, wild-type progenitor plants are resistant.  Seven-day old seedlings (PO:0007094) from the rar3 mutant and wild-type progenitor were inoculated with Bgh 5874, harvested at 16 and 32 HAI, and subjected to both Barley1 GeneChip and RNA-seq analyses.  A randomized block design with two independent biological replications was used to obtain expression measurements.  The resulting data sets are being used for two purposes; 1) transcript-based isolation of the gene(s) responsible for the rar3 phenotype, and 2) an assessment of rar3-mediated transcriptome reprogramming in both compatible and incompatible interactions in response to challenge with the biotrophic pathogen, Bgh 5874. Research supported in part by NSF Plant Genome grant #0922746.