Wang, D.Griffitts, J.Starker, C.Fedorova, E.Limpens, E.Ivanov, S.E.Bisseling, T.Long, S.Laboratorium voor Moleculaire biologiehttp://library.wur.nl/WebQuery/wurpubs/392362enjournalArticle0036-8075The nitrogen-fixing symbiosis between Sinorhizobium meliloti and its leguminous host plant Medicago truncatula occurs in a specialized root organ called the nodule. Bacteria that are released into plant cells are surrounded by a unique plant membrane compartment termed a symbiosome. We found that in the symbiosis-defective dnf1 mutant of M. truncatula, bacteroid and symbiosome development are blocked. We identified the DNF1 gene as encoding a subunit of a signal peptidase complex that is highly expressed in nodules. By analyzing data from whole-genome expression analysis, we propose that correct symbiosome development in M. truncatula requires the orderly secretion of protein constituents through coordinated up-regulation of a nodule-specific pathway exemplified by DNF12010 0036-8075 urn:nbn:nl:ui:32-392362 327 5969 1126 1129