A Rice Receptor for Mycorrhizal Fungal Signals Opens New Opportunities for the Development of Sustainable Agricultural Practices

A gap in the recognition of two mycorrhizal factors: new insights into two LysM-type mycorrhizal receptors

Arbuscular mycorrhizal (AM) fungi are crucial components of the plant microbiota and can form symbioses with 72% of land plants. Researchers have long known that AM symbioses have dramatic effects on plant performance and also provide multiple ecological services in terrestrial environments. The successful establishment of AM symbioses relies on the host plant recognition of the diffusible mycorrhizal (Myc) factors, lipo-chitooligosaccharides (LCOs) and chitooligosaccharides (COs). Among them, the short-chain COs such as CO4/5 secreted by AM fungi are the major Myc factors in COs. In this review, we summarize current advances, develop the concept of mycorrhizal biceptor complex (double receptor complexes for Myc-LCOs and CO4/5 in the same plant), and provide a perspective on the future development of mycorrhizal receptors. First, we focus on the distinct perception of two Myc factors by different host plant species, highlighting the essential role of Lysin-Motif (LysM)-type mycorrhizal receptors in perceiving them. Second, we propose the underlying molecular mechanisms by which LysM-type mycorrhizal receptors in various plants recognize both the Myc-LCOs and -COs. Finally, we explore future prospects for studies on the biceptor complex (Myc-LCO and -CO receptors) in dicots to facilitate the utilization of them in cereal crops (particularly in modern cultivated rice). In conclusion, our understanding of the precise perception processes during host plant interacting with AM fungi, where LysM-type mycorrhizal receptors act as recruiters, provides the tools to design biotechnological applications addressing agricultural challenges.

Exploring the role of plant lysin motif receptor-like kinases in regulating plant-microbe interactions in the bioenergy crop Populus

For plants, distinguishing between mutualistic and pathogenic microbes is a matter of survival. All microbes contain microbe-associated molecular patterns (MAMPs) that are perceived by plant pattern recognition receptors (PRRs). Lysin motif receptor-like kinases (LysM-RLKs) are PRRs attuned for binding and triggering a response to specific MAMPs, including chitin oligomers (COs) in fungi, lipo-chitooligosaccharides (LCOs), which are produced by mycorrhizal fungi and nitrogen-fixing rhizobial bacteria, and peptidoglycan in bacteria. The identification and characterization of LysM-RLKs in candidate bioenergy crops including Populus are limited compared to other model plant species, thus inhibiting our ability to both understand and engineer microbe-mediated gains in plant productivity. As such, we performed a sequence analysis of LysM-RLKs in the Populus genome and predicted their function based on phylogenetic analysis with known LysM-RLKs. Then, using predictive models, molecular dynamics simulations, and comparative structural analysis with previously characterized CO and LCO plant receptors, we identified probable ligand-binding sites in Populus LysM-RLKs. Using several machine learning models, we predicted remarkably consistent binding affinity rankings of Populus proteins to CO. In addition, we used a modified Random Walk with Restart network-topology based approach to identify a subset of Populus LysM-RLKs that are functionally related and propose a corresponding signal transduction cascade. Our findings provide the first look into the role of LysM-RLKs in Populus-microbe interactions and establish a crucial jumping-off point for future research efforts to understand specificity and redundancy in microbial perception mechanisms.