Figure 2

Distribution of mRNA abundances per incoming degree of connectivity in E. coli. Each graph represents the distribution of mRNA abundance for a given incoming degree of connectivity, k _in , that is the probability P(r) of finding a mRNA at abundance r for a given number of proteins regulating the corresponding genes. Graph A shows the distribution of mRNA abundance corresponding to the genes with k _in = 1, graph B for k _in = 2, graph C for k _in = 3, graph D for k _in = 4, graph E for k _in = 5 and graph F for k _in = 6. In graphs B, C and D the distribution of abundance appears clearly to follow a power-law tail which confirms the large standard deviation observed in Figure 1 when the mRNA abundance is averaged according to the incoming degree.