3 research outputs found
Evolution of Lipochitooligosaccharide Binding to a LysM-RLK for Nodulation in Medicago truncatula
International audienceLysin motif receptor–like kinases (LysM-RLKs) are involved in the perception of chitooligosaccharides (COs) and related lipochitooligosaccharides (LCOs) in plants. Expansion and divergence of the gene family during evolution have led to various roles in symbiosis and defense. By studying proteins of the LYR-IA subclass of LysM-RLKs of the Poaceae, we show here that they are high-affinity LCO-binding proteins with a lower affinity for COs, consistent with a role in LCO perception to establish arbuscular mycorrhiza (AM). In Papilionoid legumes, whole-genome duplication has resulted in two LYR-IA paralogs, MtLYR1 and MtNFP in Medicago truncatula, with MtNFP playing an essential role in root nodule symbiosis with nitrogen-fixing rhizobia. We show that MtLYR1 has retained the ancestral LCO-binding characteristic and is dispensable for AM. Domain swapping between the three LysMs of MtNFP and MtLYR1 and mutagenesis in MtLYR1 suggest that the MtLYR1 LCO-binding site is on the second LysM and that divergence in MtNFP led to better nodulation, but surprisingly with decreased LCO binding. These results suggest that divergence of the LCO-binding site has been important for the evolution of a role of MtNFP in nodulation with rhizobia
Lipo-chitooligosaccharidic Symbiotic Signals Are Recognized by LysM Receptor-Like Kinase LYR3 in the Legume <i>Medicago truncatula</i>
While
chitooligosaccharides (COs) derived from fungal chitin are
potent elicitors of defense reactions, structurally related signals
produced by certain bacteria and fungi, called lipo-chitooligosaccharides
(LCOs), play important roles in the establishment of symbioses with
plants. Understanding how plants distinguish between friend and foe
through the perception of these signals is a major challenge. We report
the synthesis of a range of COs and LCOs, including photoactivatable
probes, to characterize a membrane protein from the legume <i>Medicago truncatula.</i> By coupling photoaffinity labeling
experiments with proteomics and transcriptomics, we identified the
likely LCO-binding protein as LYR3, a lysin motif receptor-like kinase
(LysM-RLK). LYR3, expressed heterologously, exhibits high-affinity
binding to LCOs but not COs. Homology modeling, based on the <i>Arabidopsis</i> CO-binding LysM-RLK AtCERK1, suggests that LYR3
could accommodate the LCO in a conserved binding site. The identification
of LYR3 opens up ways for the molecular characterization of LCO/CO
discrimination