Inference and validation of Synechocystis protein interaction network using orthology

To better understand the response of the model cyanobacterium Synechocystis to environ mental stresses, we aim at building regulatory networks by a co mbination of gene expression data and protein-protein interactions. The experimental generation of the interaction network remains difficult, but some large-scale interaction networks are available for a nu mber of model organisms, and systematic transfer of protein-protein interactions has beco me a central task of functional genomics. Consequently, we have investigated the domain of network inference and validation through the use of protein orthologs using the concept of "interologs". In this way we expect to quantitatively expand the Synechocystis protein interaction network. We first used seven organisms separately to transfer interactions onto Synechocystis, then we combined the predictions and are now investigating the validation of these predictions using domain-domain interactions and functional annotation.