Although the legume−rhizobium symbiosis is a most-important biological process, there is a limited knowledge about the protein interaction network between host and symbiont. Using interolog- and domain-based approaches, we constructed an interspecies protein interactome containing
5115 protein−protein interactions between 2291 Glycine max
and 290 Bradyrhizobium diazoefficiens USDA 110 proteins.
The interactome was further validated by the expression
pattern analysis in nodules, gene ontology term semantic
similarity, co-expression analysis, and luciferase complementation image assay. In the G. max−B. diazoefficiens
interactome, bacterial proteins are mainly ion channel and
transporters of carbohydrates and cations, while G. max
proteins are mainly involved in the processes of metabolism,
signal transduction, and transport. We also identified the top 10 highly interacting proteins (hubs) for each species. Kyoto Encyclopedia of Genes and Genomes pathway analysis for each hub showed that a pair of 14-3-3 proteins (SGF14g and SGF14k) and 5 heat shock proteins in G. max are possibly involved in symbiosis, and 10 hubs in
B. diazoefficiens may be important symbiotic effectors. Subnetwork analysis showed that 18 symbiosis-related soluble
N-ethylmaleimide sensitive factor attachment protein receptor proteins may play roles in regulating bacterial ion channels, and SGF14g and SGF14k possibly regulate the rhizobium dicarboxylate transport protein DctA. The predicted interactome provide a valuable basis for
understanding the molecular mechanism of nodulation in soybean