Figure 6.

Clustering based on changes in expression profile between species. A, Key for the color scheme used. To aid the visualization of vectors, the angular direction of vectors (within the context of the PCs graphed) is indicated by color. The result is that vectors with similar direction (changes in expression profile between species) are shown in similar colors. B to J, Vectors (arrow base representing S. pennellii [S. penn.] and arrow tip representing S. lycopersicum [S. lyco.]) were clustered based on changes in their component PC values. Changes in PC values were each assigned to an independent layer of a superSOM, the weight of which is proportional to the variance explained by the PC. The result of the cluster analysis is groups of genes with similar changes in their expression profiles between species, regardless of their overall tissue-specific expression. Change in direction in PC space is multidimensional, which must be considered when analyzing the shared properties of vectors belonging to a distance cluster.