Analysis of microarray data. Self-organizing map (SOM) clusters of expression profiles (a) and cluster analysis of transcripts (b) from maize tissues showing different UV-B responses. RNA from the same tissues not exposed to UV-B was used as the reference. (a) Each graph displays the mean pattern of expression of the ESTs in the cluster in blue and the standard deviation of average expression (red and yellow lines). The number of ESTs in each cluster is at the bottom left corner of each SOM. The y-axis represents log2 of gene-expression levels. (b) Clustering was performed according to . The color saturation reflects the magnitude of the log2 expression ratio (Cy5/Cy3) for each transcript. Red color means higher transcript levels than the reference, whereas green means lower transcript levels than the reference. Gray corresponds to flagged ESTs that had signals similar to the background in some conditions and hence were eliminated during the analysis. The color log2 scale is provided at the bottom of the figure. Correspondence between nodes of the cluster tree and SOM clusters are indicated on vertical bars on the left side of the tree.