Bell C A, Magkourilou E, Ault J R, Urwin P E, Field K J
School of Biology, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, United Kingdom.
Plants, Photosynthesis and Soil, School of Biosciences, University of Sheffield, Sheffield, S10 2TN, United Kingdom.
Nat Commun. 2024 Jan 27;15(1):801. doi: 10.1038/s41467-024-45026-3.
Arbuscular mycorrhizal (AM) fungi associate with the roots of many plant species, enhancing their hosts access to soil nutrients whilst obtaining their carbon supply directly as photosynthates. AM fungi often face competition for plant carbon from other organisms. The mechanisms by which plants prioritise carbon allocation to mutualistic AM fungi over parasitic symbionts remain poorly understood. Here, we show that host potato plants (Solanum tuberosum cv. Désirée) selectively allocate carbon resources to tissues interacting with AM fungi rather than those interacting with phytophagous parasites (the nematode Globodera pallida). We found that plants reduce the supply of hexoses but maintain the flow of plant-derived fatty acids to AM fungi when concurrently interacting with parasites. Transcriptomic analysis suggest that plants prioritise carbon transfer to AM fungi by maintaining expression of fatty acid biosynthesis and transportation pathways, whilst decreasing the expression of mycorrhizal-induced hexose transporters. We also report similar findings from a different plant host species (Medicago truncatula) and phytophagous pest (the aphid Myzus persicae). These findings suggest a general mechanism of plant-driven resource allocation in scenarios involving multiple symbionts.
丛枝菌根（AM）真菌与许多植物物种的根系相关联，在获取宿主光合作用直接提供的碳源的同时，增强宿主对土壤养分的获取。AM真菌常常面临来自其他生物对植物碳源的竞争。植物如何将碳分配优先给予共生的AM真菌而非寄生性共生体的机制仍知之甚少。在此，我们表明宿主马铃薯植株（Solanum tuberosum cv. Désirée）会选择性地将碳资源分配给与AM真菌相互作用的组织，而非与植食性寄生虫（马铃薯苍白球孢囊线虫）相互作用的组织。我们发现，当同时与寄生虫相互作用时，植物会减少己糖供应，但维持植物源脂肪酸向AM真菌的流动。转录组分析表明，植物通过维持脂肪酸生物合成和运输途径的表达，同时降低菌根诱导的己糖转运蛋白的表达，将碳转移优先给予AM真菌。我们还报告了来自不同植物宿主物种（蒺藜苜蓿）和植食性害虫（桃蚜）的类似发现。这些发现揭示了在涉及多种共生体的情况下，植物驱动资源分配的一般机制。
