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Resistance to Fusarium head blight (FHB) (caused mainly by Fusarium graminearum Schw.) is difficult to obtain because of the quantitative nature and the numerous types of resistance involved. cDNA expression arrays have become a rapidly growing area for the identification and characterization of genes involved in complex pathways. A cDNA library was mode from wheat (Triticum aestivum L.) spikes of the variety 'Sumai 3', 24 h after inoculation with F. graminearum. Clones were sequenced and putative function assigned to each clone based on BLASTX alignments. Nylon membrane arrays were mode from the 580 unigenes present in the library, of which 75 expressed clones were induced in the first 24 h after inoculation. Of these unigenes, 14 are involved in defense response, 9 in gene expression and regulation, 29 in other cell functions, and 24 are without o known function. The induced genes catalyze key steps in the formation of lignin, energy production, and production of phytoalexins suggesting that resistance in wheat to Fusarium is provided by a different pathway then that of the hypersensitive response. Two of the induced genes, BE585589 and BE585627, were physically mapped to regions of chromosomes 3AS and 6BL, respectively, known to contain molar QTL for FHB resistance. [ABSTRACT FROM AUTHOR]

Hexaploid wheat (Triticum aestivum) contains triplicated genomes derived from three distinct species. To better understand how different genomes are coordinated in the same nucleus of the hexaploid wheat, we globally compared gene expression of a synthetic hexaploid wheat with its diploid (Aegilops tauschii) and tetraploid (T. turgidum) parents by cDNA-AFLP display. The results suggested that the expression of a significant fraction of genes was altered in the synthetic hexaploid; most appeared to be diminished and some were activated. We characterized nine cDNA clones in details. Cytogenetic as well as genomic sequence analyses indicated that the gene silencing was not due to chromosome/DNA loss but was caused by gene regulation. Northern and RT-PCR divided these genes into three groups: (I) four genes were down-regulated nonspecifically, likely involving both parental orthologues; (II) four genes were down-regulated in an orthologue-dependent manner; (III) one gene was activated specifically in the synthetic hexaploid wheat. These genes were often altered non-randomly in different synthetic hexaploids as well as natural hexaploid wheat, suggesting that many of the gene expression changes were intrinsically associated with polyploidy. [ABSTRACT FROM AUTHOR]