Improved characterization of nod factors and genetically based variation in LysM Receptor domains identify amino acids expendable for nod factor recognition in Lotus spp.
Formation of functional nodules is a complex process depending on host-microsymbiont compatibility in all developmental stages. This report uses the contrasting symbiotic phenotypes of Lotus japonicus and L. pedunculatus, inoculated with Mesorhizobium loti or the Bradyrhizobium sp. (Lotus), to investigate the role of Nod factor structure and Nod factor receptors (NFR) for rhizobial recognition, infection thread progression, and bacterial persistence within nodule cells. A key contribution was the use of 800 MHz nuclear magnetic resonance spectroscopy and ultrahigh-performance liquid chromatography coupled to quadrupole-time-of-flight mass spectrometry for Nod factor analysis. The Nod factor decorations at the nonreducing end differ between Bradyrhizobium sp. (Lotus) and M. loti, and the NFR1/NFR5 extracellular regions of L. pedunculatus and L. japonicus were found to vary in amino acid composition. Genetic transformation experiments using chimeric and wild-type receptors showed that both receptor variants recognize the structurally different Nod factors but the later symbiotic phenotype remained unchanged. These results highlight the importance of additional checkpoints during nitrogen-fixing symbiosis and define several amino acids in the LysM domains as expendable for perception of the two differentially carbamoylated Nod factors.
Bek
Anita S
AS
Centre for Carbohydrate Recognition and signalling, Department of Molecular Biology, University of Aarhus, Gustav Wieds Vej 10, Aarhus 8000 C, Denmark.
Sauer
Jørgen
J
Thygesen
Mikkel B
MB
Duus
Jens Ø
JØ
Petersen
Bent O
BO
Thirup
Søren
S
James
Euan
E
Jensen
Knud J
KJ
Stougaard
Jens
J
Radutoiu
Simona
S
D020561:Alphaproteobacteria / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D000595:Amino Acid Sequence; D000596:Amino Acids / Q000378:metabolism*; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism; D041841:Bradyrhizobiaceae / Q000235:genetics / Q000502:physiology*; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant; D018950:Lipopolysaccharide Receptors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D008070:Lipopolysaccharides / Q000737:chemistry / Q000378:metabolism; D000070116:Lotus / Q000235:genetics / Q000382:microbiology*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009586:Nitrogen Fixation / Q000235:genetics; D010641:Phenotype; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D053204:Root Nodules, Plant / Q000166:cytology / Q000378:metabolism / Q000382:microbiology*; D016415:Sequence Alignment; D013559:Symbiosis / Q000502:physiology*
D000596:Amino Acids; D001426:Bacterial Proteins; D018950:Lipopolysaccharide Receptors; D008070:Lipopolysaccharides; D010940:Plant Proteins