Aarhus, Denmark
July 30, 2020
The determination of the crystal structure of an exopolysaccharide receptor gives insight into how plants and microbes communicate and this knowledge can hopefully be used for more sustainable agriculture where microbes have an important role. Figure: Kasper Røjkjær Andersen.
An international team of researchers led by Aarhus University are the first to determine the crystal structure of an exopolysaccharide receptor. The results give insight into how plants and microbes communicate, and this knowledge can hopefully be used for more sustainable agriculture where microbes play an important role.
Exopolysaccharides (EPS) are surface-exposed carbohydrates that surround and protect bacteria and are involved in biofilm formation, cell-to-cell interactions, immune evasion, and pathogenesis. The structures and compositions of EPS synthesized by different bacteria are highly diverse and therefore a molecular fingerprint.
EPS also plays an important role for bacterial colonization and symbiosis with plants. Nitrogen-fixing soil bacteria (rhizobia) are recognized on the basis of their EPS when colonizing plant roots, judged compatible or incompatible by their legume host and allowed or denied access accordingly. The single-pass transmembrane Exopolysaccharide receptor 3 (EPR3) is responsible for monitoring EPS.
“To gain a deeper understanding of the function of this receptor, we needed to know what it looks like”, says Jaslyn Wong, who conducted this research at Aarhus University. Unfortunately, attempts to determine the structure of the ligand-binding portion of EPR3 remained unsuccessful for years, but a breakthrough was finally achieved by using llama-derived nanobodies to obtain a crystal of the receptor.
The structure revealed that EPR3 stands out from other members of the so-called LysM receptor kinases. EPR3 deviates in its ligand-binding domain from the canonical members of this receptor family and has a fold that is unique and novel for carbohydrate binding proteins.
“This is a good example of how a structure changes our view on the biology”, says Kasper Røjkjær Andersen. “We are now able to demonstrate the existence of a completely new and structurally unique class of carbohydrate receptors and find that this class is conserved in the entire plant kingdom. We did not know this before we obtained the structure and this opens for a lot of exciting biology to understand the role of the receptor“.
Jaslyn Wong adds: "Research on EPS receptors is still in its infancy, and I am excited about how this knowledge could be used and its potential implications on shaping microbiota for more sustainable agriculture".
Link to the article in Nature Communications.
DOI: 10.1038/s41467-020-17568-9
Forskere opdager en ny og unik klasse af kulhydratreceptorer
Et internationalt forskerhold ledet af Aarhus Universitet har som de første bestemt krystalstrukturen af en exopolysakkaridreceptor. De nye resultater giver et indblik i, hvordan planter og mikrober kommunikerer – en viden som på længere sigt kan danne basis for et mere bæredygtigt landbrug, hvor mikrober spiller en større rolle.
Exopolysakkarider (EPS) er kulhydrater, der omgiver og beskytter bakterier og er involveret i dannelse af biofilm, celle-til-celle-interaktioner, immununddragelse og patogenese. Strukturerne og sammensætningerne af EPS fra forskellige bakterier kan bruges som et molekylært fingeraftryk grundet deres forskelligartethed.
EPS er også vigtig for bakteriel kolonisering og symbiose med planter. Nitrogenfikserende jordbakterier (rhizobia) genkendes gennem deres EPS, når de koloniserer planterødder. De bedømmes kompatible eller inkompatible af deres bælgplantevært, som enten giver eller nægter dem adgang til roden. Planterne bruger et transmembranprotein, Exopolysaccharide receptor 3 (EPR3), til at overvåge EPS.
”For at få en dybere forståelse af denne receptors funktion, var vi nødt til at vide, hvordan den ser ud,” siger Jaslyn Wong, som udførte forskningsprojektet ved Aarhus Universitet. Strukturbestemmelsen af EPR3 mislykkedes i mange år. Men et gennembrud kom ved at bruge antistoffer (kaldet nanobodies) fra lamaer til at krystallisere receptorens ekstracellulære domæne.
Strukturen afslørede, at EPR3 er forskellig fra andre medlemmer af den såkaldte LysM receptorfamilie. EPR3 afviger i sit ligandbindende domæne fra de øvrige, sædvanlige medlemmer af familien, idet den har en fold, der er unik og ubeskreven for kulhydratbindende proteiner.
”Dette er et godt eksempel på, hvordan en struktur ændrer vores syn på biologien,” siger Kasper Røjkjær Andersen. ”Vi er nu i stand til at vise eksistensen af en komplet ny og strukturelt unik klasse af kulhydrat-receptorer – en klasse som vi nu kan finde i hele planteriget. Dette vidste vi ikke, før vi bestemte strukturen, og dette åbner op for en masse spændende biologi, der går ud på at forstå receptorens rolle”.
Jaslyn Wong tilføjer: "Forskning i EPS-receptorer er stadig i sin spæde begyndelse, og jeg er spændt på, hvordan denne viden kan bruges og dens potentielle betydning for at anvende mikroorganismer i et bæredygtigt landbrug.
Link til artiklen i Nature Communications.
DOI: 10.1038/s41467-020-17568-9
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