Expression profiling of severe growth abortion (SGA) in triploid hybrids crossed between tetraploid wheat and Aegilops umbellulata.

We have employed whole genome microarray expression profiling as a discovery platform to identify genes to alter the transcript accumulation levels in SGA plants, which are triploid hybrids crossed between tetraploid wheat and a diploid wheat relative Aegilops umbellulata. Of the up-regulated genes, cell death and carboxy-lyase activity-related genes were the most frequently found in crown tissues of SGA plants. On the other hand, photosynthesis-related genes were highly down-regulated in crown tissues of SGA plants. In addition, transcript accumulation levels of shoot apical meristem (SGA)-related genes such as knotted-1 like homeobox (Knox) genes were also repressed in SGA plants. The microarray analysis strongly suggests that an autoimmune response-like reaction might be triggered by intergenomic incompatibility between the AB and U genomes in SGA. In addition, SAM-related and cell cycle-related genes were dramatically down-regulated in crown tissues of SGA, indicating that abnormalities of SAM are associated with the abnormal growth phenotypes in SGA. 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 7-day-old crown tissues. Two independent experiments were conducted in each exprement.