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Lipid metabolism of ectomycorrhizal fungi during their spore germination and the early period of ectomycorrhizal development

外生菌根真菌孢子萌发及外生菌根发育早期的脂质代谢

基本信息

批准号：
14560134
负责人：
HATTORI Takefumi
金额：
$ 2.56万
依托单位：
KYOTO UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2002
资助国家：
日本
起止时间：
2002 至 2004
项目状态：
已结题

项目摘要

The purpose of the present study was to elucidate the mechanisms for lipid metabolism during spore germination of ECM fungus and early period of ectomycorrhizal development.At first, we have investigated growth of ectomycorrhizal(ECM) fungi, i.e. 55 strains of 32 species in 15 genera, on saturated (palmitate), monounsaturated (oleate), diunsaturated (linoleate), triunsaturated (linolenate) fatty acids and the triacyiglyceride of oleate (triolein) in order to elucidate an ability to utilize fatty acids and lipid as a carbon source for growth. Relative utilization ratios (URs, %) obtained on the basis of mycelial growth on glucose suggest that ECM fungi belonging to the family Thelephoraceae have an ability to utilize palmitate. On the other hand, ECM fungi in the genus Laccaria have an ability to utilize at least either palmitate or oleate. Furthermore, Hygropharus russula grows on palmitate, oleate and slightly on triolein. Lactarius chrysorrheus grows only on palmitate. These fatty ac … More ids- and lipid-utilizing fungi may be promising as model fungi for further elucidation of the metabolic ability to utilize fatty acids and lipid as a carbon source. On the contrary, the fungi in genus Suillus were shown to scarcely utilize fatty acids and lipid. Furthermore, most ECM fungi did not grow on either linoleate or linolenate.Secondly, we have detected the activities of glyoxylate cycle key enzymes, isocitrate lyase, malate synthase, isocitrate dehydrogenase in TCA cycle and acyl-CoA dehydrogenase in β-oxidation from spore of ectomycorrhizal fungi.Thirdly, we have conducted a model study simulating the growth of ectomycorrial fungus in early period of ectomycorrhizal development during which Laczko et al. proposed that lipid is supplied from host plant to the fungus. Thus, the changes in activities of enzymes involved in lipid metabolism and in contents of storage carbohydrates during free-living growth of ectomycorrhizal fungus Laccaria amethystea on triolein lipid were investigated. Transferring glucose-grown mycelia to a medium containing triolein as a carbon source increased the specific activities of acyl-CoA dehydrogenase, isocitrate lyase, and malate synthase up to 340%,780% and 340%, respectively, of those detected in mycelia grown on glucose, but they decreased with in 24 hrs. The contents of glycogen, trehalose and glucose in mycelia decreased rapidly during the growth on triolein and the amount of mycelia reached only 29% of that grown on glucose. Furthermore, the activities of the above three enzymes were repressed in mycelia grown in medium containing both triolein and glucose. The results suggest that L. amethystea merely utilized lipid for temporal growth when only lipid was available as a carbon source.In conclusion, lipid metabolism is suggested to be important in a limited period of life cycle of ECM fungus, because the metabolism is regulated by catabolite repression caused by glucose. Less

本研究旨在阐明ECM真菌孢子萌发和外生菌根发育早期的脂质代谢机制。首先，我们研究了外生菌根真菌(ECM)在饱和(棕榈酸)、单不饱和(油酸)、二不饱和(亚油酸)、三不饱和(亚麻酸)脂肪酸和三酸甘油酯(三油酸)上的生长情况，以阐明ECM真菌利用脂肪酸和脂肪作为碳源的能力。根据菌丝在葡萄糖上的生长得到的相对利用率(URS，%)表明，属于黄花科的ECM真菌具有利用棕榈酸酯的能力。另一方面，漆树属的ECM真菌至少有能力利用棕榈酸盐或油酸盐。此外，赤潮藻生长在棕榈酸酯、油酸盐和少量的三油酸酯上。乳菇只生长在棕榈酸酯上。这些肥大的Ac…更多利用IDs和脂肪的真菌可能有希望成为进一步阐明利用脂肪酸和脂肪作为碳源的代谢能力的模式真菌。相反，乳杆菌属真菌几乎不利用脂肪酸和脂肪。其次，我们检测了外生菌根真菌孢子中乙醛酸循环关键酶、异柠檬酸裂解酶、苹果酸合成酶、异柠檬酸脱氢酶和β氧化中的酰基辅酶A脱氢酶的活性。提出脂类由寄主植物提供给真菌。因此，研究了外生菌根真菌紫云英自由生长过程中脂代谢相关酶活性和贮藏碳水化合物含量在三油酸脂上的变化。将葡萄糖培养的菌丝体转移到以三油酸脂为碳源的培养基上，使酰基辅酶A脱氢酶、异柠檬酸裂解酶和苹果酸合成酶的比活力分别提高到葡萄糖培养菌丝体的340%、780%和340%，但在24小时内降低。菌丝体中糖原、海藻糖和葡萄糖的含量在生长过程中迅速下降，菌丝量仅为葡萄糖生长的29%。此外，在含有三酸甘油酯和葡萄糖的培养基中，上述三种酶的活性均受到抑制。这些结果表明，紫乳杆菌只能利用脂肪作为碳源进行短暂生长。综上所述，在ECM真菌有限的生命周期中，脂肪代谢是重要的，因为代谢是由葡萄糖引起的分解代谢抑制来调节的。较少