Similarities and differences between wheat and barley profiles. Panel A shows the Euclidean distance between wheat and barley expression profiles (x-axis) plotted against the Euclidean distance between their 'centered' profiles (y-axis) for the 1,875 "high quality" sequence pairs. In a centered profile, expression is measured relative to the average across tissues. Positive y-values correspond to average expression in barley greater than in wheat while negative y-values indicate average expression in wheat greater than barley. Expression profiles which have the same shape and overall magnitude of expression fall close to the origin of this plot, while expression profiles which have the same shape but are offset from each other simultaneously exhibit a small relative distance but large absolute distance (boxed region). For comparison, Panel B shows the analogous plot, on the same scale, for two barley cultivars Morex and Golden Promise (albeit over 6 rather than 13 tissues); data taken from Ref. ). Panel C shows a typical barley (solid line) and wheat (dashed line) expression profile identified from the boxed region in Panel A to be of similar shape but differing by an offset. In this case the offset corresponds to a signal intensity 8 times higher in barley than wheat. The particular example shown here corresponds to the wheat contig TaAffx.78909.1.S1_at and the barley Contig16549_at, annotated as a MYB transcription factor.