Abstract:SummaryPlants survey their environment for the presence of potentially harmful or beneficial microbes. During colonization, cell surface receptors perceive microbe‐derived or modified‐self ligands and initiate appropriate responses. The recognition of fungal chitin oligomers and the subsequent activation of plant immunity are well described. In contrast, the mechanisms underlying β‐glucan recognition and signaling activation remain largely unexplored. Here, we systematically tested immune responses towards dif… Show more
“…Bacterial EPS is only one group of such carbohydrates. Another example is short-chain and long-chain beta-glucans of bacterial or fungal origin, some of which have been shown to elicit responses in many plants 26 , 27 . Fig.…”
Receptor-mediated perception of surface-exposed carbohydrates like lipo-and exopolysaccharides (EPS) is important for non-self recognition and responses to microbial associated molecular patterns in mammals and plants. In legumes, EPS are monitored and can either block or promote symbiosis with rhizobia depending on their molecular composition. To establish a deeper understanding of receptors involved in EPS recognition, we determined the structure of the Lotus japonicus (Lotus) exopolysaccharide receptor 3 (EPR3) ectodomain. EPR3 forms a compact structure built of three putative carbohydrate-binding modules (M1, M2 and LysM3). M1 and M2 have unique βαββ and βαβ folds that have not previously been observed in carbohydrate binding proteins, while LysM3 has a canonical βααβ fold. We demonstrate that this configuration is a structural signature for a ubiquitous class of receptors in the plant kingdom. We show that EPR3 is promiscuous, suggesting that plants can monitor complex microbial communities though this class of receptors.
“…Bacterial EPS is only one group of such carbohydrates. Another example is short-chain and long-chain beta-glucans of bacterial or fungal origin, some of which have been shown to elicit responses in many plants 26 , 27 . Fig.…”
Receptor-mediated perception of surface-exposed carbohydrates like lipo-and exopolysaccharides (EPS) is important for non-self recognition and responses to microbial associated molecular patterns in mammals and plants. In legumes, EPS are monitored and can either block or promote symbiosis with rhizobia depending on their molecular composition. To establish a deeper understanding of receptors involved in EPS recognition, we determined the structure of the Lotus japonicus (Lotus) exopolysaccharide receptor 3 (EPR3) ectodomain. EPR3 forms a compact structure built of three putative carbohydrate-binding modules (M1, M2 and LysM3). M1 and M2 have unique βαββ and βαβ folds that have not previously been observed in carbohydrate binding proteins, while LysM3 has a canonical βααβ fold. We demonstrate that this configuration is a structural signature for a ubiquitous class of receptors in the plant kingdom. We show that EPR3 is promiscuous, suggesting that plants can monitor complex microbial communities though this class of receptors.
“…In A. thaliana, the six-monomer β-1,3-glucan laminarihexaose is perceived by pattern-recognition receptors belonging to the LysM family: CHITIN ELICITOR RECEPTOR KINASE 1 (CERK1), LYSIN MOTIF-CONTAINING RECEPTOR-LIKE KINASE 4 (LYK4), and LYK5 [119] ( Figure 1B). In contrast, in the case of Nicotiana benthamiana, the equivalent LysM pattern-recognition receptors were not required to detect β-1,3-glucan oligosaccharides [120].…”
Section: Perception Of Cell Wall Damage: Wall-derived Damage-associatmentioning
confidence: 88%
“…Therefore, callose-derived oligosaccharides can be considered to be both DAMPs and fungal elicitors. Recently it was shown that β-1,3-linked glucans of different degree of polymerization are indeed perceived by both monocots and dicots, activating different immunity responses [119,120]. In A. thaliana, the six-monomer β-1,3-glucan laminarihexaose is perceived by pattern-recognition receptors belonging to the LysM family: CHITIN ELICITOR RECEPTOR KINASE 1 (CERK1), LYSIN MOTIF-CONTAINING RECEPTOR-LIKE KINASE 4 (LYK4), and LYK5 [119] ( Figure 1B).…”
Section: Perception Of Cell Wall Damage: Wall-derived Damage-associatmentioning
The plant cell walls surrounding all plant cells are highly dynamic structures, which change their composition and organization in response to chemical and physical stimuli originating both in the environment and in plants themselves. They are intricately involved in all interactions between plants and their environment while also providing adaptive structural support during plant growth and development. A key mechanism contributing to these adaptive changes is the cell wall integrity (CWI) maintenance mechanism. It monitors and maintains the functional integrity of cell walls by initiating adaptive changes in cellular and cell wall metabolism. Despite its importance, both our understanding of its mode of action and knowledge regarding the molecular components that form it are limited. Intriguingly, the available evidence implicates mechanosensing in the mechanism. Here, we provide an overview of the knowledge available regarding the molecular mechanisms involved in and discuss how mechanoperception and signal transduction may contribute to plant CWI maintenance.
“…Recent work has demonstrated that LysM‐PRRs are involved in the perception by plants of 1,3‐β‐glucans isolated from fungal cell walls (Mélida et al ., 2018; Wanke et al ., 2020b). Specifically, the hexasaccharide 1,3‐β‐ d ‐(Glc) 6 (laminarihexaose) is an immune‐active structure whose recognition in Arabidopsis is CERK1‐dependent.…”
Microbial and plant cell walls have been selected by the plant immune system as a source of microbe-and plant damage-associated molecular patterns (MAMPs/DAMPs) that are perceived by extracellular ectodomains (ECDs) of plant pattern recognition receptors (PRRs) triggering immune responses. From the vast number of ligands that PRRs can bind, those composed of carbohydrate moieties are poorly studied, and only a handful of PRR/glycan pairs have been determined. Here we present a computational screening method, based on the first step of molecular dynamics simulation, that is able to predict putative ECD-PRR/ glycan interactions. This method has been developed and optimized with Arabidopsis LysM-PRR members CERK1 and LYK4, which are involved in the perception of fungal MAMPs, chitohexaose (1,4-b-D-(GlcNAc) 6) and laminarihexaose (1,3-b-D-(Glc) 6). Our in silico results predicted CERK1 interactions with 1,4-b-D-(GlcNAc) 6 whilst discarding its direct binding by LYK4. In contrast, no direct interaction between CERK1/laminarihexaose was predicted by the model despite CERK1 being required for laminarihexaose immune activation, suggesting that CERK1 may act as a co-receptor for its recognition. These in silico results were validated by isothermal titration calorimetry binding assays between these MAMPs and recombinant ECDs-LysM-PRRs. The robustness of the developed computational screening method was further validated by predicting that CERK1 does not bind the DAMP 1,4-b-D-(Glc) 6 (cellohexaose), and then probing that immune responses triggered by this DAMP were not impaired in the Arabidopsis cerk1 mutant. The computational predictive glycan/PRR binding method developed here might accelerate the discovery of protein-glycan interactions and provide information on immune responses activated by glycoligands.
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