Biology subjects

Fort, S.

Publications and source records attributed to Fort, S..

6 recordsLinked to original sources

bioRxiv2025

LysM Receptor Proteins are Required for Ectomycorrhizal Symbiosis in Poplar

Successful symbiotic associations often rely on the perception of specific microbial signals by host plants through pattern recognition receptors. LysM receptor-like kinases are key receptors in both rhizobial and arbuscular mycorrhizal symbioses. In this study, we provide the first evidence that such LysM receptor-like kinases also control the establishment of ectomycorrhizal associations in poplar. Using CRISPR/Cas9-mediated genome editing, we knocked out three NFP-like candidate genes in various combinations. We examined their roles in the perception of the ectomycorrhizal fungus Laccaria bicolor, as well as chitin oligomers and lipo-chitooligosaccharides. We demonstrate that all three receptors are necessary for the recognition of symbiosis-related signals, calcium spiking, symbiotic gene expression, and ectomycorrhizal root phenotypes.

plant biology↗

bioRxiv2025

Structural basis for size-selective perception of chitin in plants

Plants detect microbes through pattern recognition receptors that perceive conserved microbial surface motifs known as microbe-associated molecular patterns (MAMPs). LysM receptors recognize and mediate downstream responses to chitinous MAMPs. Here, we elucidate the mechanism for the specific recognition of long-chain chitin oligomers and identify a hallmark bridge domain characteristic for the CHIP receptor class. Structural analysis of receptor-ligand complexes, biochemistry, and in planta functional studies using inhibitory nanobodies reveal the mechanism of size-selective, high affinity chitin perception in Lotus japonicus and Medicago truncatula. Additionally, we identify CERKs as low-affinity, yet essential co-receptors and propose a mechanistic model for a ligand-induced core signaling heterocomplex. Our findings provide mechanistic insights into plant chitin perception and the formation of receptor complexes critical for immune signaling.

plant biology↗

bioRxiv2024

The Medicago truncatula LYR4 intracellular domain serves as a scaffold in immunity signaling independent of its phosphorylation activity

Plants perceive and respond to chitin derived from fungal cell walls through lysine motif (LysM) receptor kinases. In the model legume Medicago truncatula, CERK1 and LYR4 represent the LysM receptor pair important for chitin-triggered immunity signaling. Here, we show that both the active kinase receptor CERK1 and the pseudokinase receptor LYR4 contribute to immunity signaling, leading to the production of reactive oxygen species (ROS). We determine the crystal structure of the LYR4 core intracellular domain with a bound nucleotide analog in the active site. Biochemical characterization shows that LYR4 binds ATP and has both autophosphorylation as well as transphosphorylation activity towards CERK1. However, in planta experiments demonstrate that the phosphorylation ability is not necessary for the function of LYR4 in chitin-triggered ROS production, but that the presence of its intracellular domain is indispensable. Together, we show that in chitin-triggered immunity the intracellular domain of LYR4 serves as a signaling scaffold independent of its catalytic activity.

plant biology↗

bioRxiv2024

A new group of LysM-RLKs involved in symbiotic signal perception and arbuscular mycorrhiza establishment

Lipo-chitooligosaccharides (LCO) and short-chain chitooligosaccharides (CO) are produced by arbuscular mycorrhizal fungi (AMF) and activate the plant symbiosis signalling pathway, which is essential for mycorrhiza formation. High affinity LCO receptors belonging to the LysM receptor-like kinase (LysM-RLK) phylogenetic group LYR-IA play a role in AM establishment, but no plant high affinity short-chain CO receptors have yet been identified. Here we studied members of the uncharacterized LYR-IB group, and found that they show high affinity for LCO, short- and long-chain CO, and play a complementary role with the LYR-IA LCO receptors for AM establishment. While LYR-IB knock out mutants had a reduced AMF colonization in several species, constitutive/ectopic expression in wheat increased AMF colonization. LYR-IB function is conserved in all tested angiosperms, but in most japonica rice a deletion creates a frameshift in the gene, explaining differences in AM phenotypes between rice and other monocot single LYR-IA mutants. In conclusion, we identified a class of LysM-RLK receptors in angiosperms with new biochemical properties and a role in both LCO and CO perception for AM establishment.

plant biology↗

bioRxiv2020

Distinct genetic bases for plant root responses to lipo-chitooligosaccharide signal molecules from distinct microbial origins

O_LILipo-chitooligosaccharides (LCOs) were originally found as symbiotic signals called Nod Factors (Nod-LCOs) controlling nodulation of legumes by rhizobia. More recently LCOs were also found in symbiotic fungi and, more surprisingly, very widely in the kingdom fungi including in saprophytic and pathogenic fungi. The LCO-V(C18:1, Fuc/MeFuc), hereafter called Fung-LCOs, are the LCO structures most commonly found in fungi. This raises the question of how legume plants, such as Medicago truncatula, can perceive and discriminate between Nod-LCOs and these Fung-LCOs. C_LIO_LITo address this question, we performed a Genome Wide Association Study on 173 natural accessions of Medicago truncatula, using a root branching phenotype and a newly developed local score approach. C_LIO_LIBoth Nod- and Fung-LCOs stimulated root branching in most accessions but there was very little correlation in the ability to respond to these types of LCO molecules. Moreover, heritability of root response was higher for Nod-LCOs than for Fung-LCOs. We identified 123 loci for Nod-LCO and 71 for Fung-LCO responses, but only one was common. C_LIO_LIThis suggests that Nod- and Fung-LCOs both control root branching but use different molecular mechanisms. The tighter genetic constraint of the root response to Fung-LCOs possibly reflects the ancestral origin of the biological activity of these molecules. C_LI

plant biology↗

bioRxiv2020

Bmf Facilitates Protein Degradation and Reduces Beclin1 Ubiquitination to Inhibit Autophagy Independent of mTOR

Previous observations suggested that Bcl-2 modifying factor (Bmf) affects autophagy but the underlying mechanisms were unknown. The present studies show that Bmf inhibited the initiation and flux of autophagy in a manner that is independent of the mTOR pathway and inhibition of mTOR increased Bmf expression to temper the autophagic cell death. In mice, emphysema was observed in Bmf-deficient mice, suggesting that Bmf suppresses autophagic cell death of alveolar type II cells. Bmf deficiency increased ubiquitination of Beclin1 with K63 chains and released Beclin1 from Bcl-2. However, Bmf deficiency also increased the levels of polyubiquitinated proteins in general. In mice, Bmf-deficiency robustly increased p62 levels in all tissues analyzed, but LC3-II levels were reduced only in the hearts of old mice. Also, Bmf-deficiency caused persistent mucous cell metaplasia in mice exposed to allergen and increased levels of polyubiquitinated Muc5ac in differentiated airway epithelial cells. The reduction of ubiquitinated proteins was mediated by the BH3- and dynein binding-domains of Bmf. Together, these findings show that the primary role of Bmf is to reduce protein levels and affects K63- and K48-ubiqutination.

cell biology↗