Gene expression profiles of hybrid necrosis in synthetic hexaploid wheat

Some abnormal growth phenotypes including hybrid necrosis are often observed in F1 hybrids (genome constitution, ABD, 2n=21) and synthetic hexaploid wheat lines (AABBDD, 2n=42) which were artificially produced by crossing between tetraploid wheat (AABB, 2n=28) and Ae. tauschii (DD, 2n=14). The hybrid necrosis phenotypes are generally divided into type I and type II necrosis. In the hybrid plants showing type I necrosis, cell death occurs gradually from the older tissues. Little information about causal genes of hybrid necrosis has been reported, and the molecular mechanisms of hybrid necrosis are still largely unknown. To compare comprehensively gene expression profiles among synthetic hexaploid wheat lines showing normal growth (WT) and type I necrosis phenotypes, cDNA-AFLP analysis was performed using mRNAs from three synthetic hexaploid wheat lines between the tetraploid wheat cultivar Langdon (Ldn) with Ae. tauschii accessions, and their parental lines. In total, 769 AFLP fragments were observed using 55 selective primer sets. Ldnand Ae. tauschii-derived fragments and additional fragments in the synthetic wheat were observed and compared between the WT and type I necrosis lines. However, no significant differences were found in the number of the Ldnand Ae. tauschiiderived fragments the newly appeared between the WT and type I necrosis lines. Few genes specifically expressed in the WT and type I necrosis lines could be identified, which indicated that limited changes of the gene expression patterns might induce the phenotypic difference between the WT and type I necrosis lines.