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The rhizobial autotransporter determines the symbiotic nitrogen fixation activity of Lotus japonicus in a host-specific manner.
- Source :
-
Proceedings of the National Academy of Sciences of the United States of America [Proc Natl Acad Sci U S A] 2020 Jan 21; Vol. 117 (3), pp. 1806-1815. Date of Electronic Publication: 2020 Jan 03. - Publication Year :
- 2020
-
Abstract
- Leguminous plants establish endosymbiotic associations with rhizobia and form root nodules in which the rhizobia fix atmospheric nitrogen. The host plant and intracellular rhizobia strictly control this symbiotic nitrogen fixation. We recently reported a Lotus japonicus Fix <superscript>-</superscript> mutant, apn1 ( aspartic peptidase nodule-induced 1 ), that impairs symbiotic nitrogen fixation. APN1 encodes a nodule-specific aspartic peptidase involved in the Fix <superscript>-</superscript> phenotype in a rhizobial strain-specific manner. This host-strain specificity implies that some molecular interactions between host plant APN1 and rhizobial factors are required, although the biological function of APN1 in nodules and the mechanisms governing the interactions are unknown. To clarify how rhizobial factors are involved in strain-specific nitrogen fixation, we explored transposon mutants of Mesorhizobium loti strain TONO, which normally form Fix <superscript>-</superscript> nodules on apn1 roots, and identified TONO mutants that formed Fix <superscript>+</superscript> nodules on apn1 The identified causal gene encodes an autotransporter, part of a protein secretion system of Gram-negative bacteria. Expression of the autotransporter gene in M. loti strain MAFF3030399, which normally forms Fix <superscript>+</superscript> nodules on apn1 roots, resulted in Fix <superscript>-</superscript> nodules. The autotransporter of TONO functions to secrete a part of its own protein (a passenger domain) into extracellular spaces, and the recombinant APN1 protein cleaved the passenger protein in vitro. The M. loti autotransporter showed the activity to induce the genes involved in nodule senescence in a dose-dependent manner. Therefore, we conclude that the nodule-specific aspartic peptidase, APN1, suppresses negative effects of the rhizobial autotransporter in order to maintain effective symbiotic nitrogen fixation in root nodules.<br />Competing Interests: The authors declare no competing interest.
- Subjects :
- Bacterial Proteins chemistry
Bacterial Proteins genetics
Bacterial Proteins metabolism
Gene Expression Regulation, Plant
Genes, Bacterial genetics
Gram-Negative Bacteria
Mesorhizobium genetics
Mesorhizobium metabolism
Models, Molecular
Nitrogen Fixation genetics
Phenotype
Plant Roots growth & development
Plant Roots metabolism
Protein Conformation
Protein Domains
Rhizobium genetics
Root Nodules, Plant growth & development
Root Nodules, Plant metabolism
Symbiosis genetics
Transcriptome
Type V Secretion Systems chemistry
Type V Secretion Systems genetics
Lotus metabolism
Nitrogen Fixation physiology
Rhizobium metabolism
Symbiosis physiology
Type V Secretion Systems metabolism
Subjects
Details
- Language :
- English
- ISSN :
- 1091-6490
- Volume :
- 117
- Issue :
- 3
- Database :
- MEDLINE
- Journal :
- Proceedings of the National Academy of Sciences of the United States of America
- Publication Type :
- Academic Journal
- Accession number :
- 31900357
- Full Text :
- https://doi.org/10.1073/pnas.1913349117