|Caldo, Rico - IOWA STATE UNIVERSITY|
|Nettleton, Dan - IOWA STATE UNIVERSITY|
Submitted to: International Triticeae Mapping Initiative Workshop
Publication Type: Proceedings
Publication Acceptance Date: May 22, 2004
Publication Date: N/A
Technical Abstract: Plant recognition of pathogen-derived molecules influences attack and counter-attack strategies that affect the outcome of host-microbe interactions. To ascertain the global framework of host gene expression during biotrophic pathogen invasion, we utilized the Barley1 GeneChip probe array to analyze the transcriptional regulation of 22,792 host genes throughout 36 (genotype x pathogen x time) interactions between barley (Hordeum vulgare) and Blumeria graminis f. sp. hordei (Bgh), the causal agent of powdery mildew disease. A split-split-plot design was used to investigate near-isogenic barley lines with introgressed Mla6, Mla13, and Mla1 CC-NBS-LRR resistance alleles challenged with Bgh isolates 5874 (AvrMla6, AvrMla1) and K1 (AvrMla13, AvrMla1). A linear mixed model analysis was employed to identify genes with significant differential expression (p-value<0.0001) in incompatible and compatible barley-Bgh interactions across six time points after pathogen challenge. Twenty-two host genes, of which nine were of unknown function, exhibited highly similar patterns of up-regulation among all incompatible and compatible interactions up to 16 hours after inoculation (hai), coinciding with germination of Bgh conidiospores and formation of appressoria. In contrast, significant divergent expression was observed after 16 hai, during membrane-to-membrane contact between fungal haustoria and host epidermal cells, with notable suppression of the steady state levels of most transcripts in compatible interactions. These findings provide a link between the recognition of general and specific pathogen-associated molecules in the expression of plant defense responses and its implications on the evolution of host-specific resistance from the recognition and prevention of the pathogen's suppression of plant basal defense. Research supported by USDA-IFAFS grant no. 01-52100-11346, USDA-NRI grant no. 02-35300-12619, and the North American Barley Genome Project.