To assess the significance of the gene expression network topologies shown in Figure 1, the S. pombe and S. cerevisiae expression matrices were randomized by shuffling the values within each row and the genes were mapped in a 3-dimensional space (S. pombe in A and S. cerevisiae in B). No appreciable structure in the randomized gene expression networks were observed, suggesting that the overall observation observed with the real data has biological significance in the two yeats.