Lipid transfer from plants to arbuscular mycorrhiza fungi.
Lipid transfer from plants to arbuscular mycorrhiza fungi.
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DOI：
10.7554/elife.29107
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发表时间：
2017-07-20
期刊：
影响因子：
7.7
通讯作者：
Gutjahr C
中科院分区：
文献类型：
--
作者：
Keymer A;Pimprikar P;Wewer V;Huber C;Brands M;Bucerius SL;Delaux PM;Klingl V;Röpenack-Lahaye EV;Wang TL;Eisenreich W;Dörmann P;Parniske M;Gutjahr C
丛枝菌根（AM）共生体对全球碳循环的贡献，因为植物宿主将高达20%的光合产物转移给专性生物营养真菌。先前的研究表明，碳水化合物是转移到真菌中的唯一碳形式。然而，从头脂肪酸（FA）的合成尚未观察到在AM真菌在植物的情况下。在正向遗传学方法中，我们确定了两个Lotus突变体在AM特异性的脂质生物合成基因（KASI和GPAT 6）旁系同源物中有缺陷。这些突变体干扰真菌发育和标志性真菌16：1ω5 FA的积累。使用同位素分析，我们表明，13 C模式的真菌脂肪酸重演野生型主机，表明跨王国脂质转移从植物到真菌。对于AM特异性脂质生物合成突变体，未观察到标记的FA的这种转移。因此，有益AM真菌的生长和发育不仅由糖提供燃料，而且取决于来自植物宿主的脂质转移。http://dx.doi.org/10.7554/eLife.29107.001大多数陆地植物都能够与某些生活在土壤中的真菌--被称为丛枝菌根真菌--形成伙伴关系。这些真菌为植物提供矿物质营养，特别是磷酸盐和氮，以换取植物的碳基食物。为了交换养分，真菌生长到植物的根部，并在植物细胞内形成高度分枝的结构，称为丛枝。由于研究这种伙伴关系的困难，长期以来人们一直认为植物只为真菌提供糖。然而，最近发现这些真菌缺乏制造脂肪酸分子所需的重要基因。脂肪酸是制造更大的脂肪分子所必需的，这些脂肪分子除其他外，还为生物体储存能量，并形成包围每个细胞的膜。因此，这些结果提高了植物可能为真菌提供真菌生长所需的一些脂肪酸的可能性。Keymer，Pimprikar等人研究了一种名为Lotus Pasta的植物中丛枝的形成，Lotus Pasta是豌豆和豆类的近亲。实验鉴定了一组突变体L.有问题形成丛枝的植物。这些植物在几个参与脂肪生产的基因中发生了突变，这些基因只在含有丛枝的植物细胞中活跃。进一步的实验表明，在真菌中发现的某些脂肪分子，而不是植物，与真菌定植的正常植物样品相比，真菌定植的突变植物样品中的脂肪分子水平要低得多。这表明，真菌殖民突变植物可能是饥饿的脂肪分子。使用一种称为稳定同位素标记的技术，可以证明正常植物中产生的脂肪酸可以进入殖民真菌。Keymer，Pimprikar等人的发现提供了证据，证明植物不仅用糖而且用脂肪分子喂养真菌。下一个挑战将是找出脂肪分子是如何从植物细胞转移到真菌的。许多农作物能够与丛枝菌根真菌形成伙伴关系。因此，更好地了解脂肪分子在这些关系中的作用可能有助于培育作物植物，通过为其真菌伴侣提供更多支持，可以在田间生长得更好。DOI：http://dx.doi.org/10.7554/eLife.29107.002网站
Arbuscular mycorrhiza (AM) symbioses contribute to global carbon cycles as plant hosts divert up to 20% of photosynthate to the obligate biotrophic fungi. Previous studies suggested carbohydrates as the only form of carbon transferred to the fungi. However, de novo fatty acid (FA) synthesis has not been observed in AM fungi in absence of the plant. In a forward genetic approach, we identified two Lotus japonicus mutants defective in AM-specific paralogs of lipid biosynthesis genes (KASI and GPAT6). These mutants perturb fungal development and accumulation of emblematic fungal 16:1ω5 FAs. Using isotopolog profiling we demonstrate that 13C patterns of fungal FAs recapitulate those of wild-type hosts, indicating cross-kingdom lipid transfer from plants to fungi. This transfer of labelled FAs was not observed for the AM-specific lipid biosynthesis mutants. Thus, growth and development of beneficial AM fungi is not only fueled by sugars but depends on lipid transfer from plant hosts. DOI: http://dx.doi.org/10.7554/eLife.29107.001 Most land plants are able to form partnerships with certain fungi – known as arbuscular mycorrhiza fungi – that live in the soil. These fungi supply the plant with mineral nutrients, especially phosphate and nitrogen, in return for receiving carbon-based food from the plant. To exchange nutrients, the fungi grow into the roots of the plant and form highly branched structures known as arbuscules inside plant cells. Due to the difficulties of studying this partnership, it has long been believed that plants only provide sugars to the fungus. However, it has recently been discovered that these fungi lack important genes required to make molecules known as fatty acids. Fatty acids are needed to make larger fat molecules that, among other things, store energy for the organism and form the membranes that surround each of its cells. Therefore, these results raise the possibility that the plant may provide the fungus with some of the fatty acids the fungus needs to grow. Keymer, Pimprikar et al. studied how arbuscules form in a plant known as Lotus japonicus, a close relative of peas and beans. The experiments identified a set of mutant L. japonicus plants that had problems forming arbuscules. These plants had mutations in several genes involved in fat production that are only active in plant cells containing arbuscules. Further experiments revealed that certain fat molecules that are found in fungi, but not plants, were present at much lower levels in samples from mutant plants colonized with the fungus, compared to samples from normal plants colonized with the fungus. This suggests that the fungi colonizing the mutant plants may be starved of fat molecules. Using a technique called stable isotope labelling it was possible to show that fatty acids made in normal plants can move into the colonizing fungus. The findings of Keymer, Pimprikar et al. provide evidence that the plant feeds the fungus not only with sugars but also with fat molecules. The next challenge will be to find out exactly how the fat molecules are transferred from the plant cell to the fungus. Many crop plants are able to form partnerships with arbuscular mycorrhizal fungi. Therefore, a better understanding of the role of fat molecules in these relationships may help to breed crop plants that, by providing more support to their fungal partner, may grow better in the field. DOI: http://dx.doi.org/10.7554/eLife.29107.002