Expression analysis of defense-related genes in wheat in response to infection by Fusarium graminearum.

Fusarium head blight (FHB), caused by the fungi Fusarium graminearum and Fusarium culmorum, is a worldwide disease of wheat (Triticum aestivum L.). The Chinese cultivar Ning 7840 is one of a few wheat cultivars with resistance to FHB. GeneCalling, an open-architecture mRNA-profiling technology, was used to identify differentially expressed genes induced or suppressed in spikes of Ning 7840 after infection by F. graminearum. One hundred and twenty-five cDNA fragments representing transcripts differentially expressed in wheat spikes were identified. Based on BLASTN and BLASTX analyses, putative functions were assigned to some of the genes: 28 were assigned functions in primary metabolism and photosynthesis, 7 were involved in defense response, 14 were involved in gene expression and regulation, 24 encoded proteins associated with structure and protein synthesis, 42 lacked homology to sequences in the database, and 3 were similar to cloned multidrug resistance or disease resistance proteins. Of particular interest in this study were genes associated with resistance and defense against pathogen infection. Real-time quantitative reverse-transcription PCR indicated that of 51 genes tested, 19 showed 2-fold or greater induction or suppression in infected Ning 7840 in comparison with the water-treated control. The remaining 32 genes were not significantly induced or suppressed in infected Ning 7840 compared with the control. Subsequently, these 19 induced or suppressed genes were examined in the wheat line KS24-1, containing FHB resistance derived from Lophopyrum elongatum, and Len, an FHB-susceptible wheat cultivar. The temporal expression of some of these sequences encoding resistance proteins or defense-related proteins showed FHB (resistance specific) induction, suggesting that these genes play a role in protection against toxic compounds in plant-fungus interactions. On the basis of comprehensive expression profiling of various biotic or abiotic stress response genes revealed by quantitative PCR in this study and other supporting data, we hypothesized that the plant-pathogen interactions may be highly integrated into a network of diverse biosynthetic pathways.