A plant's measuring tape: how roots tell helpful fungi from attackers by length alone

Plants live surrounded by fungi — some feed them, some attack them — and the difference can come down to the length of a sugar chain. Researchers led by Kira Gysel and Kasper Røjkjær Andersen at Aarhus University in Denmark report in Science that a root receptor called CHIP13 works like a measuring tape: it grips long chitin chains (the building material of fungal cell walls) at several points, while short chains barely register. Long fragments mean an attack, and CHIP13 calls in a second receptor, CERK6, to switch on the plant's defences; short fragments mean a friendly symbiont, and the plant lets it in. The same trick was found in a second legume species — a hint that breeders could one day give crops a better tape measure.

SDG 2 · Zero hunger — Mechanism: tech innovation