Fungal metabolism and free amino acid content may predict nitrogen transfer to the host plant in the ectomycorrhizal relationship between Pisolithus spp. and Eucalyptus grandis

• Published in: The New phytologist 2024-05, Vol.242 (4), p.1589-1602
• Main Authors: Plett, Krista L., Wojtalewicz, Dominika, Anderson, Ian C., Plett, Jonathan M.
• Format: Article
• Language: English
• Subjects: amino acid metabolism; Amino acids; Amino Acids - metabolism; Basidiomycota - metabolism; Basidiomycota - physiology; ectomycorrhizal fungi; Ectomycorrhizas; Eucalyptus; Eucalyptus - metabolism; Eucalyptus - microbiology; Eucalyptus grandis; Fungi; Gene expression; Gene Expression Regulation, Fungal; Host plants; Isotope labelling; Labeling; Metabolism; Mycorrhizae - metabolism; Mycorrhizae - physiology; Nitrogen; Nitrogen - metabolism; nutrient transfer; Nutrients; Nutrition; Pisolithus; Plants; Radioactive labelling; Symbionts; Symbiosis; Transcriptomics
• ISSN: 0028-646X; 1469-8137
• DOI: 10.1111/nph.19400

Summary Ectomycorrhizal (ECM) fungi are crucial for tree nitrogen (N) nutrition; however, mechanisms governing N transfer from fungal tissues to the host plant are not well understood. ECM fungal isolates, even from the same species, vary considerably in their ability to support tree N nutrition, resulting in a range of often unpredictable symbiotic outcomes. In this study, we used isotopic labelling to quantify the transfer of N to the plant host by isolates from the ECM genus Pisolithus, known to have significant variability in colonisation and transfer of nutrients to a host. We considered the metabolic fate of N acquired by the fungi and found that the percentage of plant N acquired through symbiosis significantly correlated to the concentration of free amino acids in ECM extra‐radical mycelium. Transcriptomic analyses complemented these findings with isolates having high amino acid content and N transfer showing increased expression of genes related to amino acid transport and catabolic pathways. These results suggest that fungal N metabolism impacts N transfer to the host plant in this interaction and that relative N transfer may be possible to predict through basic biochemical analyses.