Wang Yaoyao, Zhao Zeyu, Liu Jiaxin, Yang Aiyiwei, Jacquemyn Hans, Yang Luna, Qian Xin, Li Taiqiang, Ding Gang, Xing Xiaoke
State Key Laboratory for Quality Ensurance and Sustainable Use of Dao-di Herbs, Institute of Medicinal Plant Development, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, 100193, China.
Department of Biology, Plant Conservation and Population Biology, Katholieke Universiteit Leuven, Leuven, B-3001, Belgium.
Sci China Life Sci. 2025 Aug 1. doi: 10.1007/s11427-025-2987-9.
Orchids critically rely on mycorrhizal fungi for seed germination and seedling development, but the extent to which the fungus benefits from the orchid is less clear. Recent work in arbuscular mycorrhizae has suggested that plants can provide fatty acids (FAs) to fungi, but empirical evidence in orchids remains limited. Here, we combine lipidomic and transcriptomic analyses to test the hypothesis that the germination-promoting fungus Ceratobasidium sp. GS2 receives carbon in the form of FAs from Gymnadenia conopsea seeds during symbiotic germination. Confocal and transmission electron microscopy confirmed the potential of FA transfer from seeds to the fungus. Symbiosis resulted in significant changes in the lipid composition of the fungus, with increased concentrations of FAs in the external mycelium. RNA-seq showed upregulation of genes associated with FA synthesis in seeds and downregulation of de novo FA synthesis genes in fungi 12 d post-symbiosis, indicating that the increased amounts of FAs in the fungus may originate from the seeds. These results indicate that FAs absorbed by hyphae in the colonized inner cortex cells support hyphal growth, providing evidence for directional carbon flow from the orchid seeds to the fungus and supporting a "give now and get now" model of mutualism in orchid-fungus symbioses.
兰花在种子萌发和幼苗发育过程中严重依赖菌根真菌，但真菌从兰花中获益的程度尚不清楚。近期丛枝菌根的研究表明，植物可以向真菌提供脂肪酸（FAs），但兰花方面的实证证据仍然有限。在这里，我们结合脂质组学和转录组学分析，来检验促进萌发的真菌角担菌属GS2在共生萌发期间从康诺顶冰花种子中获得脂肪酸形式的碳这一假设。共聚焦显微镜和透射电子显微镜证实了脂肪酸从种子转移到真菌的可能性。共生导致真菌脂质组成发生显著变化，外部菌丝体中脂肪酸浓度增加。RNA测序显示，共生12天后，种子中与脂肪酸合成相关的基因上调，而真菌中从头脂肪酸合成基因下调，这表明真菌中脂肪酸含量的增加可能源自种子。这些结果表明，被定殖的内皮层细胞中的菌丝吸收的脂肪酸支持菌丝生长，为碳从兰花种子向真菌的定向流动提供了证据，并支持兰花-真菌共生中“即时给予，即时获取”的共生模式。
