Figure 4

Principal component analysis (PCA) of the distribution of mean gene expression ratios of 234 genes (origin of vector is at the intersection of Axes 1 and 2 and the top of vector plotted as triangles) in the 35 hybridized microarrays (plotted as circles and squares) hybridized as described in Fig. 3. Arrays are labeled according to plant species and treatment (see Fig 3). Particular genes are identified with arrows. Clusters of microarrays with similar treatments are connected by lines. Axes 1 and 2 account for 40.1 and 8.3 % of the variation, respectively. Vectors of genes that are relatively long and parallel and, as such, correlated with the first canonical axis explain a large part of the variance. Vectors are strongly (up-or down) regulated in arrays and clusters of arrays lying near the end of a particular gene vector. For example, the WRKY gene vectors (originating at the intersection of Axes 1 and 2 and terminating at the WRKY gene triangle) contribute significantly to the cluster of microarrays hybridized with labeled cDNA derived from MeJA-elicited and Manduca and mirid attacked plants. Or, for example, the AOS gene vectors (originating at the intersection of Axes 1 and 2 and terminating at the AOS gene triangle) contribute significantly to the clusters of microarrays hybridized with labeled cDNA from MeJA-treated plant.