Comparative genomics. (A) Correlation between observed and predicted expression of the modules in Arabidopsis using the network inferred from Populus. The theoretically optimal prediction is also shown and indicates that all modules are predictable in Arabidopsis. The randomized curve is based on 1000 runs where the Arabidopsis genes are randomly assigned to modules. (B) The regulatory network with modules colored from green (conserved, high correlation) to red (non-conserved, low correlation) based on the expression correlation from (A). Grey modules lack homologues or expression data for their genes or regulators. Modules are labeled with the main functional annotations.