| Scope and method of study. The objective of this study was to identify and characterize differentially expressed ESTs in wheat spikes as a response to F. graminearum infection. Suppression subtraction hybridization coupled with microarray analysis of ca. 4800 cDNAs was conducted to identify differentially expressed ESTs between Fusarium head blight (FHB) resistant and susceptible varieties and also between fungal-and mock-inoculated plants. Microarray data were analyzed using GenePix Pro 5.0, GenePix Pro AutoProcessor, BLAST-X and Genesis software.; Findings and conclusions. Microarray analysis revealed ca. 290 significantly differentially expressed ESTs after imposition of fungal-stress. The identification of a large number of differentially expressed ESTs suggests that plant defense in response to FHB infection is complex and involves a regulatory network of genes involved in photosynthesis, transcription, metabolism, energy generation, protein modification, cell rescue/defense as well as genes of still unknown function. F. graminearum appears to have an antagonistic effect on photosynthesis since up-regulation of defense-related ESTs in FHB resistant varieties (relative to susceptible control) coincided with down-regulation of photosynthesis-related ESTs. Up-regulation of defense-related ESTs can occur early at 3 hours after inoculation (hai) in the resistant variety while mostly occur at 36 hai or later in the susceptible control. This indicates a slower defense response in FHB susceptible compared to resistant variety. There were more differentially induced ESTs than repressed ESTs in the resistant variety during the first 24 hai with the pathogen, but more significantly down-regulated ESTs were observed from treatments of 36 hai and onward. |
