Plant receptor CHIP13 works like a measuring tape for fungal chitin, its authors say
CHIP13, a plant receptor, binds long chitin chains much more strongly than short ones, according to a paper in Science. The team led by Kira Gysel and Kasper Røjkjær Andersen traces the preference to a bridge domain that grips the chain at several points.
The Scientist · Science desk
What happened
- Fungal growth and breakdown leave chitin fragments of different lengths in soil, and plants detect them to monitor the microbes around them.
- Long fragments are commonly associated with fungal attack and strong immune responses, while shorter ones are associated with partnerships such as nutrient-trading symbiotic fungi.
- When chitin is present, CHIP13 recruits a second receptor, CERK6, and the two form a signaling complex that activates the plant's immune system.
- Experiments that blocked either receptor confirmed the plant needs both to mount a defense response.
Why it matters
- What's now possible capability The release says the findings could help guide crop-resilience work that keeps beneficial interactions intact, an aim for later studies.
- What it limits constraint Species evidence comes from legumes, so crops outside that group have no direct support from the tests as described.
- What it sets up precedent The bridge domain is shared by a whole class of related receptors, so the next obvious test is whether the others also measure chain length.
The team combined structural biology, biochemistry and experiments in living plants [4]. The structure gives the physical reason for the preference: only chains long enough to span the grip points are held tightly [5]. Gysel, an assistant professor, put the finding in one line. "We learned that CHIP13, and specifically its bridge domain, works like a measuring tape," Gysel said [6].
First author Simon Boje Hansen described the puzzle posed by the second receptor: "We were facing a puzzle: How can CERK6 be essential for the plant's response to chitin, when it can barely hold on to it?" [10] The answer is a hand-off. Gysel said "only CERK6 can sound the alarm for the rest of the plant" [11].
"It was only when chitin was bound to CHIP13 that CHIP13 could call on CERK6," said first author Henriette Rübsam [12]. Put that beside the length preference and, in our reading, the length test sits ahead of the alarm: long chains should be the ones that recruit CERK6 most readily [16].
Rübsam added a note on scope: "Importantly, we saw that this was also true in a second legume plant, showing that this mechanism is preserved across different species." [13]
Gysel described the payoff this way: "That allows the plant to recognize signals associated specifically with a potential fungal attack and not confuse them with signals from potentially helpful microbes," Gysel said [14]. The split between attack and symbiosis is an association, and fragments of many lengths arrive together in soil [1][2]. How sharp the cutoff stays under those conditions is a separate experiment. The release does not include binding strengths, the chain lengths tested, the number of plants or which receptor, if any, reads the short fragments tied to symbiosis, so "much more strongly" cannot be sized.
Gysel looks further ahead, and conditionally: "If we can better understand this, we can start to think about designing receptors that read new signals altogether, expanding what plants are capable of sensing and responding to." [17]
What to watch
- The binding data in the paper itself: how large the long-versus-short difference is, and whether the cutoff is sharp or gradual.
- Tests in non-legume crops, since the preservation claim so far rests on a second legume.
- Work on the other bridge-domain receptors, and on which receptor reads the short fragments tied to symbiosis.
Clarity's read
What the record supports and how the coverage leans. The claims behind it follow.
Reality
- Evidence68
- Adoption
- Insufficient
- Hype gap+20
- Incentives
- Insufficient
- Confidence60
Claim ledger
Ranked by verification strength, evidence, and original report placement.
- [1]
When fungi grow or are broken down, fragments of chitin chains of different lengths end up in the soil, and plants detect them to monitor the microbes around them.
- [2]
Long chitin fragments are commonly associated with fungal attack and trigger strong plant immune responses, while shorter fragments are associated with beneficial partnerships, including interactions with symbiotic fungi that exchange essential nutrients with their hosts.
- [3]
A receptor called CHIP13 binds long chitin chains much more strongly than short ones.
- [4]
The team combined structural biology with biochemistry and experiments in living plants to investigate the receptors that detect chitin at the surface of plant root cells.
- [5]
A distinctive part of the receptor, the 'bridge domain', helps it grip the chain at several points, so that only chains long enough to span them are held tightly.
- [6]
"We learned that CHIP13, and specifically its bridge domain, works like a measuring tape," said Gysel.
- [7]
Assistant professor Kira Gysel and professor Kasper Røjkjær Andersen led the work, published in Science (2026) as 'Structural basis for size-selective perception of chitin in plants'.
- [8]
In the presence of chitin, CHIP13 recruits a second receptor, CERK6, and the two form a signaling complex that activates the plant's immune system.
- [9]
Experiments in which either receptor was blocked confirmed that the plant needs both to mount a defense response.
- [10]
"We were facing a puzzle: How can CERK6 be essential for the plant's response to chitin, when it can barely hold on to it?" said Boje Hansen.
- [11]
Gysel said CHIP13 physically comes together with CERK6, "and only CERK6 can sound the alarm for the rest of the plant".
- [12]
"It was only when chitin was bound to CHIP13 that CHIP13 could call on CERK6," said Rübsam.
- [13]
"Importantly, we saw that this was also true in a second legume plant, showing that this mechanism is preserved across different species," said Rübsam.
- [14]
"That allows the plant to recognize signals associated specifically with a potential fungal attack and not confuse them with signals from potentially helpful microbes," said Gysel.
- [15]
The bridge domain is a hallmark of a whole class of related receptors.
- [16]
Because CERK6 recruitment required chitin bound to CHIP13, and CHIP13 binds long chains much more strongly than short ones, long chains should be the ones that recruit CERK6 most readily, so the length test acts before the immune signal.
- [17]
"If we can better understand this, we can start to think about designing receptors that read new signals altogether, expanding what plants are capable of sensing and responding to," said Gysel.
- [18]
The release says insights such as these could help guide efforts to improve crop resilience while preserving beneficial interactions.
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Sources
1 independent publisher whose own reporting we read for this story.
- phys.orgPlants use a molecular measuring tape to tell fungal friend from foe
1 article · October 15, 2026
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Topics
- Structural BiologyFollow
- Plant-microbe interactionsFollow
- Plant immunityFollow