Figure 7.

Subsets of A. thaliana genes characterized by different expression intensities and specificities. Each gene is plotted according to the percentage of plant samples by which the gene specific probe has been hybridized (x-label) and to the median of expression intensities observed in the different samples (y-label). (A) First, we estimated the base line for all data (in black) and we characterized two gene groups: the highly expressed genes (HE, in magenta, 4371 genes) above the base line and the lowly expressed genes (LE, in green, 6790 genes) below the base line. Second, we identified two inflections in the base line corresponding to 15% and 85% of hybridizations (vertical dashed black lines). These limits characterized two extreme sets of genes, the genes exhibiting the Smallest Range of hybridizations (SR, 4510 genes) and the gene exhibiting the Widest Range of hybridizations (WR, 1241 genes). (B) From the SR and WR gene sets, we defined 4 sets of genes with extreme hybridization intensities by estimating an upper (magenta line) and lower (green line) bound at the 60% confidence interval. Thus, there are 618 SR-HE+, 822 SR-LE+, 244 WR-HE+ and 385 WR-LE+ genes.