Ancient tripartite coevolution in the attine ant-microbe symbiosis

The symbiosis between fungus-growing ants and the fungi they cultivate for food has been shaped by 50 million years of coevolution. Phylogenetic analyses indicate that this long coevolutionary history includes a third symbiont lineage: specialized microfungal parasites of the ants' fungus gardens. At ancient levels, the phylogenies of the three symbionts are perfectly congruent, revealing that the ant-microbe symbiosis is the product of tripartite coevolution between the farming ants, their cultivars, and the garden parasites. At recent phylogenetic levels, coevolution has been punctuated by occasional host-switching by the parasite, thus intensifying continuous coadaptation between symbionts in a tripartite arms race.     

Mutualistic fungi control crop diversity in fungus-growing ants

Leaf-cutting ants rear clonal fungi for food and transmit the fungi from mother to daughter colonies so that symbiont mixing and conflict, which result from competition between genetically different clones, are avoided. Here we show that despite millions of years of predominantly vertical transmission, the domesticated fungi actively reject mycelial fragments from neighboring colonies, and that the strength of these reactions are in proportion to the overall genetic difference between these symbionts. Fungal incompatibility compounds remain intact during ant digestion, so that fecal droplets, which are used for manuring newly grown fungus, elicit similar hostile reactions when applied to symbionts from other colonies. Symbiont control over new mycelial growth by manurial imprinting prevents the rearing of multiple crops in fungus gardens belonging to the same colony.     

Coevolved crypts and exocrine glands support mutualistic bacteria in fungus-growing ants

Attine ants engage in a quadripartite symbiosis with fungi they cultivate for food, specialized garden parasites, and parasite-inhibiting bacteria. Molecular phylogenetic evidence supports an ancient host-pathogen association between the ant-cultivar mutualism and the garden parasite. Here we show that ants rear the antibiotic-producing bacteria in elaborate cuticular crypts, supported by unique exocrine glands, and that these structures have been highly modified across the ants' evolutionary history. This specialized structural evolution, together with the absence of these bacteria and modifications in other ant genera that do not grow fungus, indicate that the bacteria have an ancient and coevolved association with the ants, their fungal cultivar, and the garden parasite.     

Fiber, food, fuel, and fungal symbionts

Virtually all plants of economic importance form mycorrhizae. These absorbing organs of higher plants result from a symbiotic union of beneficial soil fungi and feeder roots. In forestry, the manipulation of fungal symbionts ecologically adapted to the planting site can increase survival and growth of forest trees, particularly on adverse sites. Vesicular-arbuscular mycorrhizae, which occur not only on many trees but also on most cultivated crops, are undoubtedly more important to world food crops. Imperatives for mycorrhizal research in forestry and agriculture are (i) the development of mass inoculum of mycorrhizal fungi, (ii) the interdisciplinary coordination with soil management, plant breeding, cultivation practices, and pest control to ensure maximum survival and development of fungal symbionts in the soil, and (iii) the institution of nursery and field tests to determine the circumstances in which mycorrhizae benefit plant growth in forestry and agri-ecosystems.     

Fungus-growing ants

Fungus-growing ants (Attini) are in reality unique fungus-culturing insects.There are several hundred species in some dozen genera, of which Acromyrmex and Atta are the conspicuous leaf-cutters. The center of their activities is the fungus garden, which is also the site of the queen and brood. The garden, in most species, is made from fresh green leaves or other vegetal material. The ants forage for this, forming distinct trails to the vegetation that is being harvested. The cut leaves or other substrate are brought into the nest and prepared for the fungus. Fresh leaves and flowers are cut into pieces a millimeter or two in diameter; the ants form them into a pulpy mass by pinching them with the mandibles and adding saliva. Anal droplets are deposited on the pieces, which are then forced into place in the garden. Planting of the fungus is accomplished by an ant's picking up tufts of the adjacent mycelium and dotting the surface of the new substrate with it. The combination of salivary and anal secretions, together with the constant care given by the ants, facilitates the growth of the ant fungus only, despite constant possibilities for contamination. When the ants are removed, alien fungi and other organisms flourish. A mature nest of Atta Sexdens may consist of 2000 chambers, some temporarily empty, some with refuse, and the remainder with fungus gardens. Thousands of kilograms of fresh leaves will have been used. A young laboratory colony of Atta cephalotes will use 1 kilogram of fresh leaves for one garden. The attines are the chief agents for introducing organic matter into the soil in tropical rain forests; this matter becomes the nucleus for a host of other organisms, including nematodes and arthropods, after it is discarded by the ants. One ant species cultures a yeast; all others grow a mycelium. In the higher species the mycelium forms clusters of inflated hyphae. Mycologists accept as valid two names for confirmed fruiting stages: Leucocoprinus ( or Leucoagaricus) gongylophora (Moeller 1893) and Lepiota n. sp.     

秦岭楼观台油松林地3种土栖性蚂蚁巢内真菌多样性研究(英文)

研究比较了秦岭楼观台油松林地日本弓背蚁(Camponotus japonicus)、铺道蚁(Tetramo-riumcaespitum)及日本黑褐蚁(Formicajaponica)3种蚂蚁蚁巢内外土壤真菌多样性的差异。研究结果表明:(1)从3种蚂蚁蚁巢及无蚂蚁栖居的土壤样品中共分离到15种真菌,无蚂蚁栖居土壤中真菌种类是3种蚂蚁巢内真菌种类的2.0~3.5倍;日本弓背蚁巢内平均cfu.g-1最低,明显低于无蚂蚁栖居的土壤(P<0.05),另外2种蚂蚁巢内及其无蚂蚁栖居的土壤平均cfu.g-1差异不明显(P>0.05)。(2)3种蚂蚁蚁巢内的真菌多样性指数(H′)均显著低于无蚂蚁栖居的土壤(P<0.05),但在3种蚂蚁蚁巢之间无显著差异(P>0.05);3种蚂蚁及无蚂蚁栖居的土壤的真菌均匀度指数(E)之间无显著差异(P>0.05)。(3)3种蚂蚁巢内真菌种类组成明显不同,形成各自特殊的真菌群落;蚁巢中分布的真菌种类几乎都可发现于无蚂蚁栖居的土壤,但其在蚁巢内的分布均大于无蚂蚁栖居的土壤。不同蚂蚁蚁巢内及无蚂蚁栖居的土壤中真菌组成及其多样性的差异与土壤微环境以及不同蚂蚁种群、筑巢习性及其对真菌的防卫机制密切相关。     

野生兰属植物根部内生真菌多样性初步研究

采集生长在我国广西、贵州、云南的密林、开阔地两种生境的9种兰属植物,对其根部的内生真菌进行分离,经过形态观察和ITS序列测定相结合的鉴定。结果表明,分离得到的99个菌株隶属于29个菌属。对子囊菌和担子菌分别进行的系统发育树构建结果显示,子囊菌为优势菌种,其中镰刀菌属（Fusarium,22.20%）,炭角菌属（Xylaria,6.06%）和木霉属（Trichoderma,5.05%）为优势菌属。物种丰富度和Simpson多样性指数（D）分析结果表明,密林生境的兰属植物的菌根真菌多样性高于开阔生境。     

AM真菌在植物病虫害生物防治中的作用机制

丛枝菌根(Arbuscular Mycorrhizae,AM)真菌是一类广泛分布于土壤生态系统中的有益微生物,能与大约80%的陆生高等植物形成共生体。由土传病原物侵染引起的土传病害被植物病理学界认定为最难防治的病害之一。研究表明,AM真菌能够拮抗由真菌、线虫、细菌等病原体引起的土传性植物病害,诱导宿主植物增强对病虫害的耐/抗病性。当前,利用AM真菌开展病虫害的生物防治已经引起生态学家和植物病理学家的广泛关注。基于此,围绕AM真菌在植物病虫害生物防治中的最新研究进展,从AM真菌改变植物根系形态结构、调节次生代谢产物的合成、改善植物根际微环境、与病原微生物直接竞争入侵位点和营养分配、诱导植株体内抗病防御体系的形成等角度,探究AM真菌在植物病虫害防治中的作用机理,以期为利用AM真菌开展植物病虫害的生物防治提供理论依据,并对本领域未来的发展方向和应用前景进行展望。     

AM真菌与植物的互作及其对植物种间竞争的影响

 丛植菌根（AM）是自然界广泛存在的一种植物根系与菌根真菌的共生体。种间竞争是群落中不同物种之间由于资源的稀缺性和可利用性之间的差异而产生的相互竞争效应。二者均是影响植物群落结构和功能的重要因素。因而探究AM真菌和植物种间竞争之间的相互作用,对于揭示植物群落的动态变化、结构组成以及维持群落的稳定性和多样性具有重要的意义。基于此,本文以丛枝菌根真菌为中心,在探讨AM真菌与植物互作效应的基础上,通过对AM真菌与植物群落的排除效应和共存效应的机理分析,探究AM真菌对植物种间竞争的影响,同时对AM真菌与种间竞争未来的研究方向进行了展望。     

The Paleozoic origin of enzymatic lignin decomposition reconstructed from 31 fungal genomes

Wood is a major pool of organic carbon that is highly resistant to decay, owing largely to the presence of lignin. The only organisms capable of substantial lignin decay are white rot fungi in the Agaricomycetes, which also contains non-lignin-degrading brown rot and ectomycorrhizal species. Comparative analyses of 31 fungal genomes (12 generated for this study) suggest that lignin-degrading peroxidases expanded in the lineage leading to the ancestor of the Agaricomycetes, which is reconstructed as a white rot species, and then contracted in parallel lineages leading to brown rot and mycorrhizal species. Molecular clock analyses suggest that the origin of lignin degradation might have coincided with the sharp decrease in the rate of organic carbon burial around the end of the Carboniferous period.     

春兰与4种菌根真菌共生产生的植物激素

为探明菌根真菌促进春兰生长发育的作用机制,从与4种菌根真菌(Rhizoctonia-like的CLB111,CLB113,MLX102及KW214菌株)的共生春兰菌根中提取植物激素,用高效液相色谱进行梯度洗脱,并对其进行分析鉴定。结果表明:4种共生体均能不同程度地产生赤霉素(GA3)、吲哚乙酸(IAA)、脱落酸(ABA)、玉米素(Z)和玉米素核苷(ZR)5种植物激素,其中CLB111共生体产生的GA3达306.875ng/mL;而MLX102共生体产生的IAA和ZR是4种共生体中最多的,分别达537.567ng/mL和69.32ng/mL;ABA和Z在KW214共生体中产生的量最多。菌根真菌与春兰共生后促进激素释放,从而促进春兰生长。     

Comparative analysis of protein kinases and associated domains between Ascomycota and Basidiomycota

Protein kinases play an important role in every aspect of cellular life. In this study, we systemically identified protein kinases from the predicted proteomes of 59 representative fungi from Ascomycota and Basidiomycota. Comparative analysis revealed that fungi from Ascomycota and Basidiomycota differed in the number and variety of protein kinases. Some groups of protein kinases, such as calmodulin/calcium regulated kinases (CMGC) and those with the highest group percentages are the most prevalent protein kinases among all fungal species tested. In contrast, the STE group (homologs of the yeast STE7, STE11 and STE20 genes), was more abundant in Basidiomycetes than in Ascomycetes. Importantly, the distribution of some protein kinase families appeared to be subphylum-specific. The tyrosine kinase-like (TKL) group had a higher protein kinase density in Agaricomycotina fungi. In addition, the distribution of accessory domains, which could have functional implications, demonstrated that usage bias varied between the two phyla. Principal component analysis revealed a divergence between the main functional domains and associated domains in fungi. This study provides novel insights into the variety and expansion of fungal protein kinases between Ascomycota and Basidiomycota.     

两种烟草根结线虫生防菌对土壤中微生物数量的影响

以前期筛选出的对烟草根结线虫防治效果较好的两种担子菌进行田间试验,研究不同处理下烟草根际土壤中可培养真菌、细菌及放线菌的变化。结果表明:两种生防担子菌有效抑制了烟草根际中烟草根结线虫二龄幼虫的数量,还能显著增加土壤中可培养真菌、细菌及放线菌数量;其中,毛头鬼伞菌对土壤中可培养放线菌数量的影响最为显著。     

土壤类型和树种对根际土丛枝菌根真菌群落及其根系侵染率的影响

为合理利用丛枝菌根(Arbuscular Mycorrhiza,AM)真菌促进喀斯特退化土地植被恢复,采用形态学方法研究了土壤类型(石灰土和黄壤)和宿主植物种类(紫弹树(Celtis biondii Pamp)、红锥(Castanopsis hystrix)和单性木兰(Kmeria septentrionalis Dandy))对AM真菌群落结构的影响。研究共分离鉴定了2属14种AM真菌,其中幼套球囊霉(Glomus etunicatum)是石灰土和黄壤共有的优势种,石灰土特有的AM真菌包括地球囊霉(G.geosporum)、白色球囊霉(G.albidum)、双型球囊霉(G.ambisporum)、象牙白球囊霉(G.eburneum)和细凹无梗囊霉(G.scrobiculata),而波状无梗囊霉(A.undulata)是黄壤特有的AM真菌。土壤类型对AM真菌孢子密度,Shannon多样性指数以及侵染率具有显著影响;宿主植物种类与AM真菌Shannon多样性指数呈显著相关。石灰土紫弹树和单性木兰根际土AM真菌孢子丰度显著高于黄壤相同植物的,而红锥无显著差异;石灰土紫弹树和红锥的AM真菌物种丰富度及Shannon多样性指数均高于黄壤同种植物的。土壤类型对AM真菌孢子密度、物种丰富度、Shannon多样性指数和侵染率均有显著影响,对均匀度指数也有显著影响;植物种类对Shannon多样性指数有显著影响,且AM真菌物种丰富度、Shannon多样性指数和侵染率受土壤类型与植物种类交互作用的显著影响;土壤p H和全钾含量对AM真菌群落影响显著。因此,利用AM真菌促进喀斯特植物定植生长与植被恢复过程中,应该考虑喀斯特土壤AM真菌具有区域特异性和物种偏好性。     

Rapid turnover of hyphae of mycorrhizal fungi determined by AMS microanalysis of 14C

Processes in the soil remain among the least well-characterized components of the carbon cycle. Arbuscular mycorrhizal (AM) fungi are ubiquitous root symbionts in many terrestrial ecosystems and account for a large fraction of photosynthate in a wide range of ecosystems; they therefore play a key role in the terrestrial carbon cycle. A large part of the fungal mycelium is outside the root (the extraradical mycelium, ERM) and, because of the dispersed growth pattern and the small diameter of the hyphae (<5 micrometers), exceptionally difficult to study quantitatively. Critically, the longevity of these fine hyphae has never been measured, although it is assumed to be short. To quantify carbon turnover in these hyphae, we exposed mycorrhizal plants to fossil ("carbon-14-dead") carbon dioxide and collected samples of ERM hyphae (up to 116 micrograms) over the following 29 days. Analyses of their carbon-14 content by accelerator mass spectrometry (AMS) showed that most ERM hyphae of AM fungi live, on average, 5 to 6 days. This high turnover rate reveals a large and rapid mycorrhizal pathway of carbon in the soil carbon cycle.     

The evolution of agriculture in ants

Cultivation of fungi for food by fungus-growing ants (Attini: Formicidae) originated about 50 million years ago. The subsequent evolutionary history of this agricultural symbiosis was inferred from phylogenetic and population-genetic patterns of 553 cultivars isolated from gardens of "primitive" fungus-growing ants. These patterns indicate that fungus-growing ants succeeded at domesticating multiple cultivars, that the ants are capable of switching to novel cultivars, that single ant species farm a diversity of cultivars, and that cultivars are shared occasionally between distantly related ant species, probably by lateral transfer between ant colonies.     

果园脐腹小蠹伴生(共生)真菌群落组成及功能分析

【目的】研究新疆果树脐腹小蠹伴生真菌种类或类群,分析其功能,为脐腹小蠹为害机理和伴生真菌开发利用提供基础信息。【方法】在新疆疏勒、英吉沙等地采集被害果树上的脐腹小蠹成虫,利用MiSeq高通量测序技术和室内分离培养的方法,鉴定其伴生真菌种类或类群,通过FUNGuild功能预测和查阅相关文献,分析其功能。【结果】脐腹小蠹伴生真菌主要由7个门、24个纲、66个目、124个科的221个属组成;体表和肠道伴生真菌群落无显著性差异,体表伴生真菌优势菌群为Geosmithia、Saccharomycetales、Byssochlamys和 Wickerhamomyces,分别占群落的29.55%、19.50%、8.20%和6.07%;而肠道伴生真菌优势菌群为Geosmithia、Pleosporales和 Gibellulopsis,分别占42.14%,15.61%和6.97%;伴生真菌以腐生营养型、植物致病性、病理-腐生营养型和动物致病性为主,且不同果树脐腹小蠹均携带植物病致病性真菌,其中桃树脐腹小蠹携带植物致病型真菌比例最高,为19.06%;室内分离鉴定出伴生真菌13种,其中Geosmithia pallida、Yamadazyma mexicana和Cladosporium macrocarpum为植物病原菌,Wickerhamomyces silvicola、Meyerozyma guilliermondii、Rhodotorula mucilaginosa和Aureobasidium pullulans为多种植物病原菌的拮抗菌。【结论】新疆果树脐腹小蠹普遍携带、传播植物病原真菌,在防控脐腹小蠹的同时应注重果树枝干病害的防控,防止2类有害生物协同为害,加重危害;而伴生真菌中的有益拮抗菌可作为植物病害的生物防治菌被开发利用。     

Thallphytic alleopathy: isolation and identification of laetisaric Acid

Laetisaria arvalis, a soil-dwelling basidiomycete fungus, secretes an allelopathic agent that induces rapid hyphal lysis in several phytopathogenic fungi. The active compound was isolated from chloroform:methanol extracts of L. arvalis mycelia and characterized as a previously unknown hydroxy fatty acid, (Z,Z-9,12-8-hydroxyoctadecadienoic acid.     

Glomalean fungi from the Ordovician

Fossilized fungal hyphae and spores from the Ordovician of Wisconsin (with an age of about 460 million years) strongly resemble modern arbuscular mycorrhizal fungi (Glomales, Zygomycetes). These fossils indicate that Glomales-like fungi were present at a time when the land flora most likely only consisted of plants on the bryophytic level. Thus, these fungi may have played a crucial role in facilitating the colonization of land by plants, and the fossils support molecular estimates of fungal phylogeny that place the origin of the major groups of terrestrial fungi (Ascomycota, Basidiomycota, and Glomales) around 600 million years ago.     

牛粪好氧堆肥中真菌群落组成的动态特征

采用高通量测序技术,探究牛粪堆肥过程中真菌群落时空动态变化、营养型及理化参数对真菌群落结构组成影响。结果表明,牛粪堆肥中未分类子囊菌门(Ascomycota)在升温期相对丰度最高,鬼伞属(Coprinus)和Guehomyces为高温期优势菌群,未分类子囊菌门为降温期优势菌属,未分类散囊菌目(Eurotiales)和Zopfiella为腐熟期优势菌群。在空间层次上,Guehomyces和未分类散囊菌目为上层和中层优势菌群,鬼伞属(Coprinus)和Zopfiella为下层优势菌群。在牛粪堆肥过程中腐生真菌相对丰度逐渐升高,堆肥下层相对丰度高于上、下两层。冗余分析(RDA)表明,含水率和温度对真菌群落结构变化影响显著(P0.05)。牛粪堆肥过程中真菌群落结构组成在不同时期和空间上均存在差异,堆肥内真菌群落多数为腐生营养型,真菌群落结构变化与理化因子相关。