Aegilops tauschii x Triticum turgidum Transcriptome or Gene expression. Aegilops tauschii x Triticum turgidum

Common wheat is an allohexaploid species, derived through endoreduplication of an inter-specific triploid hybrid produced from a cross between cultivated tetraploid wheat and the wild diploid relative Aegilops tauschii Coss. Hybrid incompatibilities, including hybrid necrosis, have been observed in triploid wheat hybrids. A limited number of Ae. tauschii accessions show hybrid lethality in triploid hybrids crossed with tetraploid wheat due to developmental arrest at the early seedling stage, which is termed severe growth abortion (SGA). Despite the potential severity of this condition, the genetic mechanisms underlying SGA are not well understood. We conducted comparative analyses of gene expression profiles in crown tissues to characterize developmental arrest in triploid hybrids displaying SGA. A number of defense-related genes were highly up-regulated, whereas many transcription factor genes, such as the KNOTTED1-type homeobox gene, which function in shoot apical meristem (SAM) and leaf primordia, were down-regulated in the crown tissues of SGA plants. Transcript accumulation levels of cell cycle-related genes were also markedly reduced in SGA plants, and no histone H4-expressing cells were observed in the SAM of SGA hybrid plants. Our findings demonstrate that SGA shows unique features among other types of abnormal growth phenotypes, such as type II and III necrosis. Overall design: Expression patterns were compared between the two triploid hybrids showing the wild-type phenotype (as a reference) and severe growth abortion. Total RNA samples were isolated from the 3-week-old crown tissues. Two independent experiments were conducted in each exprement.