Expression Analysis and Physical Mapping of a cDNA Library of Fusarium Head Blight Infected Wheat Spikes

Abstract

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 made 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 made 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 a 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 than 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 major QTL for FHB resistance.