Figure legend : (A) Ortholog genes between the budding and fission yeasts were independently represented in a 3-dimensional space according to their expression measurements during the time course experiments described in Mata et al. 2002 and Chu et al. 1998. Points represent the 98 and 85 genes belonging to the S. pombe (green) and S. cerevisiae (blue) genomes respectively. White segments link pairs of genes for which the inter-gene distance between their expression measurements is less than a threshold D0 = 0.3 (a conventional correlation higher than 0.95).
(B) Initial superimposition of the 3D-gene expression networks shown in (A). Ortholog gene pairs are connected with red segments.
(C) Result of the superimposition after the optimization procedure described in Methods. Only the S. cerevisiae genome (blue) was displaced, with a w-value = 2. During the optimisation, the S. cerevisiae gene expression network was completely turned over. For instance, the genes YJR152W and YIR029W, initially located on the right side were finally found on the left side (vertical arrows). Likewise, the gene YHR087W, initially located at the top of the gene expression network was finally found at the bottom (horizontal arrow). 3D visualizations and snapshots were obtained with the rgl package.