New Unique Class of Carbohydrate Receptors Discovered
The crystal structure of an exopolysaccharide receptor has been determined for the first time by an international team of researchers led by Aarhus University. Insights into how microbes and plants communicate are provided in the results and this information can be used for more sustainable agriculture where microbes play an important role.
Exopolysaccharides (EPS) are involved in biofilm formation, pathogenesis, immune evasion, and cell-to-cell interactions, and are surface-exposed carbohydrates that surround and protect bacteria. The compositions and structures synthesized by different bacteria are molecular fingerprints as they are highly diverse.
In bacterial colonization and symbiosis with plants, EPS plays an important role. When colonizing plant roots, on the basis of the EPS, the nitrogen-fixing soil bacteria (rhizobia) are recognized, judged compatible, or incompatible by their legume host, and accordingly, they are allowed or denied. For monitoring EPS, the single-pass transmembrane EPR3, Exopolysaccharide receptor 3 is responsible.
At Aarhus University, Jaslyn Wong, who conducted this research said, “We needed to know what the receptor looks like in order to gain a deeper understanding of the function of this receptor.” To obtain a crystal of the receptor, a breakthrough was finally achieved now by using
llama-derived nanobodies, after the attempts to determine the structure of the ligand-binding portion of EPR3 remained unsuccessful for years.From other members of the so-called LysM receptor kinases, the structure revealed that EPR3 stands out. EPR3 has a fold that is unique and novel for carbohydrate-binding proteins and deviates in its ligand-binding domain from the canonical members of this receptor family.
Kasper Røjkjær Andersen says, “The existence of a structurally unique and completely new class of carbohydrate receptors has been demonstrated and we have found that this class is conserved in the entire plant kingdom. This opens for a lot of exciting biology to understand the role of the receptor as we did not know this before we obtained the structure.”
Jaslyn Wong added saying that research on EPS receptors is still in its infancy, it is exciting to know its potential implications on shaping microbiota for more sustainable agriculture and how this knowledge could be used.
