Gene Expression Profiling Soybean Stem Tissue Early Response to Sclerotinia sclerotiorum and In Silico Mapping in Relation to Resistance Markers

White mold, caused by Sclerotinia sclerotiorum (Lib.) de Bary, can be a serious disease of crops grown under cool, moist environments. In many plants, such as soybean [Glycine max (L.) Merr.], complete genetic resistance does not exist. To identify possible genes involved in defense against this pathogen, and to determine possible physiological changes that occur during infection, a microarray screen was conducted using stem tissue to evaluate changes in gene expression between partially resistant and susceptible soybean genotypes at 8 and 14 hours post inoculation. RNA from 15 day-old inoculated plants was labeled and hybridized to soybean cDNA microarrays. ANOVA identified 1270 significant genes from the comparison between time points and 105 genes from the comparison between genotypes. Selected genes were classified into functional categories. The analyses identified changes in cell-wall composition and signaling pathways, as well as suggesting a role for anthocyanin and anthocyanidin synthesis in the defense against S. sclerotiorum. In-silico mapping of both the differentially expressed transcripts and of public markers associated with partial resistance to white mold, provided evidence of several differentially expressed genes being closely positioned to white mold resistance markers, with the two most promising genes encoding a PR-5 and anthocyanidin synthase.