Abstract
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.
Publication types
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Research Support, N.I.H., Extramural
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, Non-P.H.S.
MeSH terms
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Endoplasmic Reticulum / metabolism
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Gene Expression
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Gene Expression Profiling
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Genes, Plant
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Medicago truncatula / genetics
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Medicago truncatula / metabolism*
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Medicago truncatula / microbiology*
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Membrane Proteins / genetics
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Membrane Proteins / metabolism*
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Mutation
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Nitrogen Fixation*
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Plant Proteins / genetics
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Plant Proteins / metabolism
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Plants, Genetically Modified
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Protein Subunits / genetics
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Protein Subunits / metabolism
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Root Nodules, Plant / metabolism
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Root Nodules, Plant / microbiology*
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Secretory Pathway*
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Serine Endopeptidases / genetics
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Serine Endopeptidases / metabolism*
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Sinorhizobium meliloti / physiology*
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Symbiosis*
Substances
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Membrane Proteins
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Plant Proteins
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Protein Subunits
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Serine Endopeptidases
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type I signal peptidase