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Mix of LCOs and COs essential for mycorrhizal establishment

last modified Nov 08, 2019 12:54 PM
An international collaboration of scientists working to optimise arbuscular mycorrhizal associations to improve sustainability in agriculture has demonstrated new insights into how signalling pathways promote symbiotic microbial associations with plants.

A model for COs/PGN and LCO recognition during symbiosis.
A model for COs/PGN and LCO recognition during symbiosis. Graphic by Feng Feng.

The team from the University of Cambridge, Aarhus University, Université de Grenoble Alpes and University of Copenhagen demonstrated that a combination of chitooligosaccharides (COs) and lipochitooligosaccharides (LCOs) promote symbiotic associations in Medicago truncatula.

They showed that that COs ranging from CO4-CO8 can induce symbiosis signalling in Medicago truncatula and all of these molecules also activate immunity signalling. CO4 and CO8 perception is a function of the receptor-like kinases MtCERK1 and LYR4, that activate both immunity and symbiosis signalling. A combination of LCOs and COs acts synergistically to enhance symbiosis signalling and suppress immunity signalling and receptors involved in both CO and LCO perception are necessary for mycorrhizal establishment.

“We show that COs cannot be separated into those that activate symbiosis versus immunity responses, rather it appears that COs equally elicit symbiotic and immunity signaling, with longer chain COs, such as CO8, showing greater activity. Receptors responsible for both CO and LCO recognition are required in the establishment of arbuscular mycorrhizal associations and demonstrate how the recognition of mixes of COs and LCOs emphasises a symbiotic, over immunogenic, response. We conclude that LCOs, when present in a mix with COs, drive a symbiotic outcome and this mix of signals is essential for mycorrhizal establishment.”

Read the full article in Nature Communications.

Feng Feng, Jongho Sun, Guru V. Radhakrishnan, Tak Lee, Zoltán Bozsóki, Sébastien Fort, Aleksander Gavrin, Kira Gysel, Mikkel B. Thygesen, Kasper Røjkjær Andersen, Simona Radutoiu, Jens Stougaard & Giles E. D. Oldroyd. A combination of chitooligosaccharide and lipochitooligosaccharide recognition promotes arbuscular mycorrhizal associations in Medicago truncatula. Nature Communications (November 2019). DOI: 10.1038/s41467-019-12999-5

COs and LCOs activate symbiotic calcium oscillations.
COs and LCOs activate symbiotic calcium oscillations.




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