Stimulation of asymbiotic sporulation in arbuscular mycorrhizal fungi by fatty acids
Stimulation of asymbiotic sporulation in arbuscular mycorrhizal fungi by fatty acids
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DOI：
10.1038/s41564-019-0485-7
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发表时间：
2019-10-01
影响因子：
28.3
通讯作者：
Akiyama, Kohki
中科院分区：
文献类型：
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作者：
Kameoka, Hiromu;Tsutsui, Ippo;Akiyama, Kohki
丛枝菌根（AM）真菌是专性共生体，依赖于活的宿主植物完成其生命周期（1，2）。这一特性导致了AM真菌在无植物条件下的不可培养性，严重阻碍了AM真菌的基础研究和农业应用。然而，至少一种AM真菌可以在与细菌类芽孢杆菌（Paenibacillus validus）共培养的情况下独立于宿主植物生长和发育可育孢子（3）。细菌来源的物质被认为是真菌孢子形成的刺激物或营养物，但这些分子尚未得到鉴定。在这里，我们表明，（S）-12-甲基十四烷酸（4，5），从细菌培养物中分离的甲基支链脂肪酸，刺激从母孢子萌发的菌丝的分支和次生孢子在AM真菌Rhizophagus irregularis的无菌培养物的形成。对脂肪酸的广泛测试表明，棕榈油酸比细菌脂肪酸在R。不规则的这些诱导的孢子具有感染宿主植物根并产生子孢子的能力。我们的工作表明，除了有机碳（6-9）的主要来源，脂肪酸作为刺激剂，诱导感染能力的次生孢子在非共生阶段，并可能提供的关键，发展无菌生产的AM接种物。
Arbuscular mycorrhizal (AM) fungi are obligate symbionts that depend on living host plants to complete their life cycle(1,2). This feature, which leads to their unculturability in the absence of plants, strongly hinders basic research and agricultural application of AM fungi. However, at least one AM fungus can grow and develop fertile spores independently of a host plant in co-culture with the bacterium Paenibacillus validus(3). The bacteria-derived substances are thought to act as stimulants or nutrients for fungal sporulation, but these molecules have not been identified. Here, we show that (S)-12-methyltetradecanoic acid(4,5), a methyl branched-chain fatty acid isolated from bacterial cultures, stimulates the branching of hyphae germinated from mother spores and the formation of secondary spores in axenic culture of the AM fungus Rhizophagus irregularis. Extensive testing of fatty acids revealed that palmitoleic acid induces more secondary spores than the bacterial fatty acid in R. irregularis. These induced spores have the ability to infect host plant roots and to generate daughter spores. Our work shows that, in addition to a major source of organic carbon(6-9), fatty acids act as stimulants to induce infection-competent secondary spores in the asymbiotic stage and could provide the key to developing the axenic production of AM inoculum.