Abstract
Legumes engage in root endosymbioses with both nitrogen-fixing rhizobial bacteria and phosphorus-acquiring arbuscular mycorrhizal fungi. Genetic programs in host plants for establishment of both symbioses share common symbiosis genes, mutations of which cause impaired symbiosis phenotype. Symbiosis-receptor kinase (SYMRK) was identified as a common symbiosis gene from a legume Lotus japonicus. The symrk mutant phenotype indicates that SYMRK functions in an early signaling network responding to the microbal symbiotic signals, but the direct SYMRK downstream components have not been identified prior to this study.
To identify SYMRK interacting partners, we performed yeast two hybrid screening using the SYMRK intracellular domain as a bait. We identified 4 homologues of the Drosophila Seven in Absentia (SINA) as SYMRK interactors. We designated these genes as Seven In Absentita homologue of Lotus japonicus (SIAL) 1 to 4. SIAL1-4 showed different interaction specificities to SYMRK, suggesting multiple roles of SIAL proteins in root symbioses.
