DIFFERENTIAL DISPLAY ANALYSIS IDENTIFIES POSSIBLE GENES FOR RESISTANCE AGAINST Septoria tritici BLOTCH IN WHEAT

USDA-ARS, Department of Botany and Plant Pathology, 1155 Lilly Hall, Purdue University, West Lafayette, IN, 47907-1155, USA

Differential display was used to compare gene expression in resistant and susceptible wheat lines following inoculation with the septoria tritici blotch pathogen, Mycosphaerella graminicola, as part of a project to analyze the functional genomics of pest resistance in cereal crops. Treatments consisted of the susceptible cultivar Yecora Rojo and the resistant cultivar Tadinia uninoculated, and the same two cultivars inoculated with an Indiana isolate of M. graminicola. Tadinia possesses Stb4, a single, dominant gene for resistance. Leaf tissue was collected at 0, 3, 6, 12, 24, 48 and 96 hours after inoculation, with a final sampling after 4 weeks. Total RNA was extracted and subjected to differential display using three specific and eight random primers. Following electrophoresis on denaturing sequencing gels and autoradiography, differentially expressed genes were excised from the gels, cloned and sequenced. Most sequences had no matches in GenBank. However, three clones had high similarity to a pathogenesis-related protein from Phaseolus vulgaris, one was a protein disulfide isomerase and two were probably cutinase. Surprisingly, most genes were expressed following inoculation in both the susceptible and the resistant host. Northern analysis showed that the gene for protein disulfide isomerase was expressed in both the resistant and susceptible host at 3 and 6 hours following inoculation, but that expression was much stronger in the resistant than the susceptible host.