| Root rot pathogens are important in limiting the yield of many crops, yet little genetic work has been done to characterize the genetic response of plants to these organisms. A genomics approach was used to profile the transcript response in wheat, Triticum aestivum L., roots to infection by the root rot pathogen, Pythium arrhenomanes. Three early stages of infection, hyphae colonization of root epidermis surface, penetration of the epidermis, and penetration of the cortex were determined by microscopy to occur at 3, 6, and 9 hours, respectively. cDNA libraries produced through subtraction suppression hybridization were used to constructed microarrays. These arrays were probed with fluorescently labeled mRNAs from infected and non-infected tissues in competitive hybridization experiments in order to monitor the expression of wheat root transcripts during these early stages of infection. 3,234 wheat ESTs were arrayed and 115 were found to be significantly differentially expressed at one or more infection stages. While most of these ESTs had no homology to known genes, some have homology to genes associated with nuclear, mitochondrial, plastid, or other processes. Few ESTs were found to be homologous with those differentially expressed in other microarray experiments examining salt and water deficit stress suggesting that a susceptibility response to Pythium root rot disease involves different pathways and response mechanisms than those manifested in other stress responses. |
