The host plant Pinus pinaster exerts specific effects on phosphate efflux and polyphosphate metabolism of the ectomycorrhizal fungus Hebeloma cylindrosporum: a radiotracer, cytological staining and 31P NMR spectroscopy study

Margarita Torres-Aquino (1) , Adeline Becquer (1) , Christine Le Guernevé (2) , Julien Louche (1) , Laurie Amenc (1) , Siobhan Staunton (1) , Herve Quiquampoix (1) , Claude Plassard (1)

1 UMR Eco&Sols - Ecologie fonctionnelle et biogéochimie des sols et des agro-écosystèmes
2 SPO - Sciences Pour l'Oenologie

Ectomycorrhizal (ECM) association can improve plant phosphorus (P) nutrition. Polyphosphates (polyP), synthesized in distant fungal cells after P uptake may contribute to P supply from the fungus to the host plant if they are hydrolyzed to phosphate in ECM roots then transferred to the host plant when required. In this study, we addressed this hypothesis for the ECM fungus Hebeloma cylindrosporum grown in vitro and incubated without plant or with host (Pinus pinaster) and non-host (Zea mays) plants, using an experimental system simulating the symbiotic interface. We used 32P labelling to quantify P accumulation and P efflux and in vivo and in vitro NMR spectroscopy and cytological staining to follow the fate of fungal polyP. Phosphate supply triggered a massive P accumulation as newly synthesized long-chain polyP in H. cylindrosporum if previously grown under P-deficient conditions. P efflux from H. cylindrosporum towards the roots was stimulated by both host and non-host plants. However, the host plant enhanced 32P release compared to the non-host plant and specifically increased the proportion of short-chain polyP in the interacting mycelia. These results support the existence of specific host-plant effects on fungal P metabolism able to provide P in the apoplast of ectomycorrhizal roots.

Mots clés: Fungal P efflux; Polyphosphates; 32P labelling; in vivo 31P NMR spectroscopy; maritime pine; indian corn; nmr spectrometry

Mots clés: champignon ectomycorhizien; hebeloma cylindrosporum; pinus pinaster; zea mays; spectrométrie rmn; technique de marquage; accumulation du phosphore; polyphosphate; cytologie

Domaines: Biologie végétale

Margarita Torres-Aquino, Adeline Becquer, Christine Le Guernevé, Julien Louche, Laurie Amenc, et al.. The host plant Pinus pinaster exerts specific effects on phosphate efflux and polyphosphate metabolism of the ectomycorrhizal fungus Hebeloma cylindrosporum: a radiotracer, cytological staining and 31P NMR spectroscopy study. Plant, Cell and Environment, 2017, 40 (2), pp.190-202. ⟨10.1111/pce.12847⟩. ⟨hal-01837808⟩