Mapping of genes expressed in Fusarium graminearum-infected heads of wheat cultivar 'Frontana'.

The isolation, physical, and genetic mapping of a group of wheat genes expressed in infected heads of Triticum aestivum 'Frontana' resistant to Fusarium head blight is reported. A cDNA library was built from heads of 'Frontana' through suppressive subtractive hybridization, to enrich for sequences induced by the pathogen Fusarium graminearum during infection. A group of 1794 clones was screened by dot blot hybridization for differential gene expression following infection. Twenty of these clones showed a strong difference in intensity of hybridization between infected and mock-inoculated wheat head samples, suggesting that they corresponded to genes induced during infection. The 20 clones were sequenced and used for mapping analysis. We determined a precise chromosomal location for 14 selected clones by using series of chromosome deletion stocks. It was shown that the 14 clones detected 90 fragments with the use of the restriction enzyme EcoRI; 52 bands were assigned to chromosome bins, whereas 38 fragments could not be assigned. The selected clones were also screened for polymorphisms on a 'Wuhan' x 'Maringa' wheat doubled haploid mapping population. One clone, Ta01_02b03, was related to a quantitative trait locus for type II resistance located on chromosome 2AL, as determined with simple sequence repeat markers on another mapping population, but did not map in the same location on our population. Another clone, Ta01_06f04, was identified by BLAST (basic local alignment search tool) search in public databases to code for a novel beta-1,3-glucanase, homologous to a major pathogenesis-related protein. This clone mapped to chromosomal regions on chromosome 3, including 3BL and 3DL, where B glucanase gene clusters are known to exist. Seven other clones, including 1 coding for an ethylene-response element binding protein and 3 for ribosomal proteins, and 4 clones corresponding to proteins with unknown function, were also mapped.