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The CEP peptide-CRA2 receptor module promotes arbuscular mycorrhizal symbiosis

The CEP peptide-CRA2 receptor module promoting root competence for symbiotic nodulation also promotes arbuscular mycorrhizal symbiosis

C-terminally encoded peptides (CEPs) are small secreted signaling peptides that promote nitrogen-fixing root nodulation symbiosis in legumes depending on soil mineral nitrogen availability. In the Medicago truncatula model legume plant, their action is mediated by the leucine-rich repeat receptor-like protein kinase COMPACT ROOT ARCHITECTURE 2 (CRA2). Like most land plants, under inorganic phosphate limitation, M. truncatula establishes another root endosymbiotic interaction with arbuscular fungi, the arbuscular mycorrhizal symbiosis (AMS). Because this interaction is beneficial for the plant but has a high energetic cost, it is tightly controlled by host plants to limit fungal infections mainly depending on phosphate availability. In a study published in Current Biology by the F. Frugier team at IPS2, in collaboration with Nicolas Frey-dit-Frei at the LRSV (Toulouse), we showed that the expression of a subset of CEP-encoding genes is enhanced in the low-phosphate conditions. In addition, overexpression of one of these low-phosphate-induced CEP gene, MtCEP1, previously shown to promote the nitrogen-fixing root nodulation symbiosis, enhances AMS from the initial entry point of the fungi. Conversely, a loss-of-function mutation of the CRA2 receptor required for mediating CEP peptide action decreases the endomycorrhizal interaction from the same initial fungal entry stage. Transcriptomic analyses revealed that the cra2 mutant is negatively affected in the regulation of key phosphate transport and response genes as well as in the biosynthesis of strigolactone hormones that are required for establishing AMS. Accordingly, strigolactone contents were drastically decreased in cra2 mutant roots. Overall, we showed that the CEP/CRA2 pathway promotes both root nodulation and AMS in legume plants, depending on soil mineral nutrient availability.

The CEP peptide-CRA2 receptor module promotes arbuscular mycorrhizal symbiosis. A subset of C-terminally Encoded Peptides (CEP) hormones is induced by low inorganic phosphate (Pi) conditions to promote the mycorrhizal endosymbiotic interaction with plant roots through the Compact Root Architecture 2 (CRA2) receptor and the downstream regulation of Pi homeostasis and Strigolactone hormone biosynthesis.
The CEP peptide-CRA2 receptor module promotes arbuscular mycorrhizal symbiosis. A subset of C-terminally Encoded Peptides (CEP) hormones is induced by low inorganic phosphate (Pi) conditions to promote the mycorrhizal endosymbiotic interaction with plant roots through the Compact Root Architecture 2 (CRA2) receptor and the downstream regulation of Pi homeostasis and Strigolactone hormone biosynthesis.

04/11/2024