Nodule-Specific Protein Secretory Pathway Required for Nitrogen-Fixing Symbiosis

• Published in: Science (American Association for the Advancement of Science) Vol. 327; no. 5969; pp. 1126 - 1129
• Main Authors: Wang, Dong, Griffitts, Joel, Starker, Colby, Fedorova, Elena, Limpens, Erik, Ivanov, Sergey, Bisseling, Ton, Long, Sharon
• Format: Journal Article
• Language: English
• Published: United States American Association for the Advancement of Science 26.02.2010; The American Association for the Advancement of Science
• Subjects: Bacteria; Bacteroids; define; Developmental biology; Endoplasmic Reticulum - metabolism; endoplasmic-reticulum; fixation; Gene Expression; Gene Expression Profiling; Genes; Genes, Plant; Genomics; Infections; Legumes; Medicago truncatula; Medicago truncatula - genetics; Medicago truncatula - metabolism; Medicago truncatula - microbiology; membrane; Membrane Proteins - genetics; Membrane Proteins - metabolism; mutants; Mutation; Nitrogen; Nitrogen Fixation; Nodules; plant; Plant cells; Plant Proteins - genetics; Plant Proteins - metabolism; Plants; Plants, Genetically Modified; Protein Subunits - genetics; Protein Subunits - metabolism; Proteins; Root Nodules, Plant - metabolism; Root Nodules, Plant - microbiology; root-nodules; Secretory Pathway; Serine Endopeptidases - genetics; Serine Endopeptidases - metabolism; signal peptidase activity; Sinorhizobium meliloti; Sinorhizobium meliloti - physiology; Symbiosis
• ISSN: 0036-8075; 1095-9203
• DOI: 10.1126/science.1184096

The 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 DNF1.