Myristate can be used as a carbon and energy source for the asymbiotic growth of arbuscular mycorrhizal fungi
Myristate can be used as a carbon and energy source for the asymbiotic growth of arbuscular mycorrhizal fungi
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DOI：
10.1073/pnas.2006948117
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发表时间：
2020-10-13
影响因子：
11.1
通讯作者：
Saito, Katsuharu
中科院分区：
文献类型：
--
作者：
Sugiura, Yuta;Akiyama, Rei;Saito, Katsuharu
丛枝菌根真菌（AM）与陆地植物形成共生关系，是专性共生体，没有宿主就不能完成其自然生命周期。最近的研究表明，寄主植物合成的脂质被转移到真菌中，而真菌缺乏编码胞质脂肪酸合成酶的基因，这支持了AM真菌的脂肪酸营养不良。因此，为了建立AM真菌的非共生培养体系，我们试图鉴定能促进生物量产生的脂肪酸。为了确定AM真菌是否可以在非共生条件下在脂肪酸或脂质培养基上生长，我们测试了8种饱和或不饱和脂肪酸（C12至C18）和两种ss-单酰基甘油。只有肉豆蔻酸盐（C14:0）能增加不规则根噬菌的生物量，诱导大量菌丝生长并形成具有侵染能力的次生孢子。然而，这样的孢子比共生产生的孢子要小。此外，我们还证明了r.r irregularis可以在其分支菌丝中吸收脂肪酸，并利用肉豆蔻酸盐作为碳和能量来源。肉豆蔻酸盐还能促进嗜根菌和玛格丽塔菌的生长。最后，与单独施用肉豆蔻酸盐相比，肉豆蔻酸盐和棕榈酸盐的混合物加速了真菌的生长，并诱导了三酰甘油脂肪酸组成的实质性变化，尽管在该培养体系中棕榈酸盐没有被用作细胞壁生物合成的碳源。我们的研究结果表明，肉豆蔻酸盐促进AM真菌的非共生生长，也可以作为碳和能量的来源。
Arbuscular mycorrhizal (AM) fungi, forming symbiotic associations with land plants, are obligate symbionts that cannot complete their natural life cycle without a host. The fatty acid auxotrophy of AM fungi is supported by recent studies showing that lipids synthesized by the host plants are transferred to the fungi, and that the latter lack genes encoding cytosolic fatty acid synthases. Therefore, to establish an asymbiotic cultivation system for AM fungi, we tried to identify the fatty acids that could promote biomass production. To determine whether AM fungi can grow on medium supplied with fatty acids or lipids under asymbiotic conditions, we tested eight saturated or unsaturated fatty acids (C12 to C18) and two ss-monoacylglycerols. Only myristate (C14:0) led to an increase in the biomass of Rhizophagus irregularis, inducing extensive hyphal growth and formation of infection-competent secondary spores. However, such spores were smaller than those generated symbiotically. Furthermore, we demonstrated that R. irregularis can take up fatty acids in its branched hyphae and use myristate as a carbon and energy source. Myristate also promoted the growth of Rhizophagus clarus and Gigaspora margarita. Finally, mixtures of myristate and palmitate accelerated fungal growth and induced a substantial change in fatty acid composition of triacylglycerol compared with single myristate application, although palmitate was not used as a carbon source for cell wall biosynthesis in this culture system. Our findings demonstrate that myristate boosts the asymbiotic growth of AM fungi and can also serve as a carbon and energy source.