2026-04-30 神戸大学
神戸大学と総合地球環境学研究所の研究チームは、菌根ネットワークを介した植物間の炭素移動を評価する新たな指標を提案した。アミノ酸ごとの窒素安定同位体比に着目し、通常は変化しにくいフェニルアラニンの同位体比が、菌から炭素供給を受ける菌従属栄養植物で顕著に上昇することを発見。この特徴を利用することで、従来困難だった植物間の炭素移動の有無や程度を高精度に判別できる可能性が示された。従来のラベリング法に代わる実用的手法として、森林生態系における資源分配や「wood-wide web」の実態解明に貢献する成果である。
アミノ酸の窒素安定同位体比は、植物間炭素移動を読み解く「ものさし」となり得る ©末次健司（CC BY)
＜関連情報＞
- https://www.kobe-u.ac.jp/ja/news/article/20260430-67767/
- https://nph.onlinelibrary.wiley.com/doi/10.1111/nph.71154
フェニルアラニン15Nの濃縮は、菌類群全体にわたる菌従属栄養植物における菌類由来の有機栄養素の獲得を示している可能性が高い Phenylalanine 15N enrichment likely indicates fungal-derived organic nutrient acquisition in mycoheterotrophic plants across fungal guilds
Kenji Suetsugu, Chikage Yoshimizu, Jun Matsubayashi, Ichiro Tayasu
New Phytologist Published: 29 April 2026
DOI:https://doi.org/10.1111/nph.71154
Summary
- Beyond fully mycoheterotrophic plants, many green plants may also obtain carbon from fungal partners. However, bulk stable isotope analyses often lack sufficient resolution in arbuscular mycorrhizal and rhizoctonia-associated orchid systems, limiting inference of fungal-derived organic nutrient acquisition.
- We measured δ15N values of glutamic acid (δ15NGlu) and phenylalanine (δ15NPhe) in 10 fully mycoheterotrophic species spanning arbuscular mycorrhizal, ectomycorrhizal, and saprotrophic fungal guilds, as well as in three photosynthetic species with contrasting inferred nutritional modes, together with co-occurring autotrophic references and, where available, fungal material. This Glu-Phe framework was originally developed for animal food-web studies, in which trophic position is estimated from strong 15NGlu enrichment (c. 7–8‰ per trophic step) and minimal 15NPhe enrichment (c. 0–1‰).
- We found that mycoheterotrophic plants invert this pattern, showing minimal 15NGlu enrichment (−1.2 to 3.3‰) but pronounced 15NPhe enrichment (11.2 to 19.6‰) relative to their fungal partners. They also exhibited amino acid δ15N profiles distinct from autotrophs, consistent with uptake of fungal-derived organic nitrogen.
- To our knowledge, such strong 15NPhe enrichment relative to nutrient sources has not been reported in other organisms. Overall, amino acid δ15N profiles complement bulk δ2H, δ13C, and δ15N values for assessing fungal-derived organic nutrient acquisition in green plants.
