禾草内生真菌作为生防因子的潜力分析

早熟禾亚科多种禾草可与Neotyphodium内生真菌形成禾草-内生真菌共生体, 这种植物-微生物共生体性状较为稳定, 且在自然界中广泛存在。禾草-内生真菌共生体稳定的互利共生关系不但保证了内生真菌所需的全部营养物质, 而且共生体产生的次生代谢物又可显著提高宿主禾草对生物胁迫的抗逆性。众多研究表明, 内生真菌的侵染可显著提高宿主禾草对虫害、病害及伴生植物等多种生物胁迫的抗性。据不完全统计, 禾草内生真菌对蛛形纲、线虫纲、昆虫纲3个纲至少79个种的害虫表现出较明显的抗性, 对至少22个种的病原真菌表现出明显的抗性。尽管利用内生真菌进行禾草品种选育及其品质改良的技术日趋成熟, 但是内生真菌在不同宿主禾草之间高效的替代转化技术, 及其在宿主体内遗传的稳定性仍有待于进一步深入探索。研究者把禾草内生真菌作为生防手段, 在未来的应用过程中不应只考虑其与宿主禾草之间的共生特异性, 而应更全面地分析禾草-内生真菌-生态环境之间的相互关系, 让内生真菌更好地为人类服务。     

基于act序列中国西部披碱草属植物所带内生真菌的系统演化

摘要:【目的】研究中国西部披碱草属植物(Elymus spp.)所带无性世代内生真菌的系统进化关系。【方法】克隆15条分离于中国西部披碱草属植物无性世代内生真菌肌动蛋白基因(act)序列,并与下载自GenBank中内生真菌的act序列共同构建系统进化树和网络结构拓扑图。【结果】供试无性世代内生真菌act序列均为单拷贝基因。系统进化关系表明,它们与分离于北美洲披碱草属植物的有性世代内生真菌Epichlo elymi存在不同的起源,而与分离于北美洲直芒草(Achnatherum eminens)的无性世代内生真菌Neotyphodium chisosum具有较近的亲缘关系。进一步研究发现,由北美洲直芒草无性世代内生真菌N.chisosum形成的单元型Hap 8与本研究菌株所组成的单元型Hap 3之间可能存在基因流。     

植物与内生真菌互作的生理与分子机制研究进展

在自然生态系统中,植物组织可作为许多微生物定居的生态位.内生真菌普遍存在于植物组织内,与宿主建立复杂的相互作用(互惠、拮抗和中性之间的相互转化),并且存在不同的传播方式(垂直和水平传播).内生真菌通过多样化途径来增强植物体的营养生理和抗性机能.但这种生理功能的实现有赖于双方精细的调控机制,表明宿主和真菌双方都进化形成特有的分子调控机制来维持这种互惠共生关系.环境因子(如气候、土壤性质等)、宿主种类和生理状态、真菌基因型的变化都将改变互作结果.此外,菌根真菌和真菌病毒等也可能普遍参与植物-内生真菌共生体,形成三重互作体系,最终影响宿主的表型.研究试图从形态、生理和分子水平阐述内生真菌与植物互作的基础.     

真菌与植物共生机制研究进展

真菌与植物共生是一种非常普遍、复杂和重要的生物学现象。真菌与植物共生部位、共生类型和共生结构的多样性,以及参入共生的真菌和植物多样性奠定真菌与植物共生的生物学基础。真菌与植物首先通过分子"对话"的生化机制相互识别构建共生体,进而由真菌和植物双方生理机制调控共生体发育及其生理功能,以构建稳定有效的共生体。真菌与植物的空间、营养和功能生态位很多是相近的,双方均面临相同的生态选择压力,需要共同抵抗不良生境,以适应更多环境。因此,真菌和植物通过两者共生的生态学机制增强植物抗逆性,减轻有害生物危害,提高其竞争力和生境的适应能力。真菌和植物长期的协同演化过程中,种群间的基因交流及其差异导致不同的基因组合,奠定了共生体多样化的基础与资源。此遗传学机制形成的多种遗传组合的共生体不仅使真菌和植物在各环境压力下共存,还可以不断进化发展。真菌和植物共生研究方面已形成较为完善的体系,加强真菌与植物共生理论的研究,特别是该类共生体遗传背景、基因与环境互作效应及其机制的阐明,将有助于诠释真菌与植物共生的生物学机制。     

《菌物学报》“菌根真菌专刊”征稿通知

<正>真菌与植物关系密切、共同发展、协同进化,在自然界长期演化过程中,真菌与植物逐渐建立了共生关系。业已证实,菌根真菌与植物根系建立的共生体是生物圈内典型的互惠共生关系。菌根真菌几乎涉及真菌界所有门类。其中,丛枝菌根真菌(AMF)属于专性活体营养的共生真菌,已分离鉴定近300种,隶属球囊菌门1纲4目11科25属;外生菌根真菌隶属担子菌门、子囊菌门、接合菌门和无性态真菌,全球约5 000~6 000种,     

禾草类内生真菌的研究进展*

感染内生真菌的禾草在牧草和草坪业上具有重要的生态和经济意义。关于禾草和内生真菌的互利共生作用已有大量报道,中就近年来有关禾草类内生真菌的起源和进化、内生真菌的生物和生态学作用以及内生真菌的应用前景方面的研究进展作一综述,以期更好地利用内生真菌造福人类。     

植物内生菌是有待深入开发的资源宝库

植物内生菌是指那些在其生活史的一定阶段或者全部阶段生活于健康植物各种组织和器官内部的真菌或者细菌,被感染的宿主植物(至少是暂时)不表现出外在症状。在长期的协同进化过程中,大部分植物内生菌都与植物形成了互惠互利的关系,在从宿主那里获得稳定的生活环境的同时,可增强或赋予宿主抗病、抗干旱、固氮等能力,或通过其代谢产物促进植物的生长;有些内生菌还被发现能够产生与宿主相同或相似的活性物质。因此对植物内生菌的研究从20     

禾草内生真菌对其它微生物的影响研究进展

禾草内生真菌在宿主植物的茎叶等地上组织中普遍存在,不仅能够提高禾草对生物与非生物逆境的抗性,而且能够对周围环境中的不同微生物类群产生影响。主要总结了禾草Neotyphodium/Epichlo内生真菌对病原真菌、丛枝菌根真菌和土壤微生物的影响及其作用机理。发现禾草内生真菌普遍存在对病原真菌的抑制作用,而对丛枝菌根真菌存在不对称的竞争作用,且因种类而异。禾草内生真菌对土壤微生物群落的作用则会随着土壤类型和时间等外界因素发生变化。禾草内生真菌对不同类群微生物的影响机制主要包括:通过生态位竞争、抑菌物质分泌、诱导抗病性等对病原真菌造成影响;通过根系化学物质释放、营养元素调节、侵染条件差异等对丛枝菌根真菌造成影响;通过根际沉积物和凋落物等对土壤微生物群落造成影响。禾草内生真菌产生的生物碱能提高宿主植物对包括昆虫在内草食动物采食的抗性,影响病原菌的侵入、定殖和扩展;根组织分泌物中包含次生代谢产物能够抑制菌根真菌、土传病原真菌及其它土壤微生物的侵染与群落组成;也可能通过次生代谢物影响禾草的其它抗性。因此,禾草内生真菌在植物-微生物系统中的作用应该给予更多的关注和深入研究。     

内生真菌提高禾草抗盐碱性研究进展

盐碱会导致植株生长缓慢,甚至抑制其正常发育,如何降低高盐和高p H对植物的不利影响,已成为农业持续发展的重大课题。近年来,内生和共生真菌对宿主植物在抗盐碱方面的有益作用也引起了研究人员的广泛关注。综述了内生真菌对宿主禾草植物抗盐碱性影响的研究成果,首先评述了内生真菌对宿主禾草在盐碱胁迫下种子萌发和生长发育影响表现在:提高种子发芽率;促进胚芽和胚根生长;提高宿主禾草的分蘖数、叶片数、株高、生物量、根冠比、成熟花序长度、种子数和种子产量。但也有感染内生真菌对宿主在盐胁迫下无促进作用的。其次,评述了内生真菌在减少禾草盐碱胁迫的原初盐害方面作用表现为:影响膜透性、提高光合作用、增加水分利用效率、改变营养代谢和离子毒害、影响植物激素代谢。最后综述了内生真菌在减少禾草次生盐害方面作用,内生真菌具有促进禾草分泌抗氧化剂、增加抗氧化酶活性、调节有机渗透物质的作用。系统的归纳了内生真菌与宿主禾草抗盐碱性相关研究成果,提出未来可能的研究问题和方向为后期的科研提供参考。     

内生真菌提高禾草抗盐碱性研究进展

盐碱会导致植株生长缓慢甚至抑制其正常发育,如何降低高盐和高p H对植物的不利影响,已成为农业持续发展的重大课题。近年来,内生和共生真菌对宿主植物在抗盐碱方面的有益作用也引起了研究人员的广泛兴趣。本综述评述了内生真菌对宿主禾草植物抗盐碱性影响的研究成果,首先评述了内生真菌对宿主禾草在盐碱胁迫下种子萌发和生长发育影响:表现在提高种子发芽率;促进胚芽和胚根生长;提高宿主禾草的分蘖数、叶片数、株高、生物量、根冠比、成熟花序长度、种子数和种子产量。但也有感染内生真菌对宿主在盐胁迫下无促进作用的。其次,评述了内生真菌在减少禾草盐碱胁迫的原初盐害方面作用:表现为影响膜透性、提高光合作用、增加水分利用效率、改变营养代谢和离子毒害、影响植物激素代谢。最后综述了内生真菌在减少禾草次生盐害方面作用,内生真菌具有促进禾草分泌抗氧化剂、增加抗氧化酶活性、调节有机渗透物质的作用。系统的归纳了内生真菌与宿主禾草抗盐碱性相关研究成果,提出未来可能的研究问题和方向为后期的科研提供参考。     

Mutualistic asexual endophytes in a native grass are usually parasitic

Asexual systemic fungi that live symbiotically within grasses are viewed as strong mutualists on the basis of theory and empirical studies of introduced agronomic grasses. Evolutionary theory predicts that microbial symbionts that lose sexuality and rely on propagules of their hosts for transmission should evolve to benefit their hosts. Fungal endophytes of some cultivated turf and pasture grasses are well known for increasing plant performance and competitive abilities, especially under stress, and increasing resistance to herbivores, pathogens, and root-feeders by virtue of fungal alkaloids. The assumption of mutualism, however, has rarely been tested in native grasses, which often harbor high but variable frequencies of systemic asexual endophytes. We tested the effect of Neotyphodium infections for the native grass Arizona fescue in a 3-yr field experiment. We strictly controlled host genotype and manipulated soil moisture and nutrients. Infection generally decreased host growth in terms of plant volume, number of tillers, and dry mass of shoots and roots. Infected plants also showed decreased reproduction in terms of number and mass of seeds, and the seeds produced by infected plants had lower germination success than plants without their endophytes, suggesting that the negative effects of the symbiont are transferred to the next generation. Plant genotype strongly influenced host's growth and reproduction and interacted with the presence of the endophyte, but the interaction was usually in the direction of negative effects. Our results challenge the notion that systemic asexual endophytes must be plant mutualists for infections to persist in nature. We propose other hypotheses to explain the variable but usually high endophyte frequencies in natural populations of grasses.     

Z-3-Hexenylacetate emissions induced by the endophyte Epichloë occultans at different levels of defoliation during the host plant's life cycle

Vertically transmitted fungal endophytes are common defensive symbionts of cool-season grasses. Protection against herbivores has been generally associated with alkaloids produced in the grass-endophyte symbiosis. However, many other changes occur in host metabolism like the release of VOCs. We aimed at characterizing the profile of volatile organic compounds (VOCs) induced by simultaneous fungal endophyte symbiosis and defoliation during the entire life cycle of the annual host grass and the asexual symbiont. We designed an outdoor factorial experiment with plots dominated by intact and damaged Lolium multiflorum plants with high and low infection levels with Epichloë occultans. After exploring the entire VOC profile, the green leaf volatile (Z)-3-hexenyl acetate (Z3-HAC) was found as the main compound emitted by the plants under field conditions. While in low-infected patches there were no differences in volatile emission during the plant life cycle, highly infected patches emitted more Z3-HAC in seedling and vegetative phases than in the reproductive phase. The role of Z3-HAC provided by symbiotic to neighbouring non-symbiotic plants in the associational protection against herbivores and fungal pathogens is discussed.     

内蒙古中东部草原羽茅内生真菌的遗传多样性

该文从形态学和基因水平上对内蒙古中东部草原4个羽茅(Achnatherum sibiricum)种群所含的27个内生真菌(Neotyphodium)菌株的遗传多样性进行了研究,结果表明羽茅内生真菌在形态学和基因水平上均表现出较高的遗传多样性。在PDA培养基上,根据菌落颜色、质地、生长速率和分生孢子外观等特征,可分为4个形态型;西乌旗、霍林郭勒和定位站3个种群所含的内生真菌菌落具有相似的生长特性和外观,而羊草(Leymus chinensis)样地种群无论从菌落外观和质地的多样性,还是遗传多样性指数均高于其它3个样地。用20个随机引物对这27株内生真菌基因组DNA进行RAPD分析,共检测到463个位点,其中461个为多态位点,多态位点百分率达99.6%,特有位点93个,占20.1%。Nei基因多样性指数h和Shannon多样性指数I分别为 0.238 0和0.387 0;多数菌株间的遗传一致度较低而遗传距离较大,在DNA水平上存在较显著的遗传变异。基于Nei无偏遗传距离和UPGMA法的聚类分析结果将27株内生真菌分为7组,并且与形态型的划分基本一致,RAPD分析方法提高了内生真菌类群划分的可靠性。     

禾草-内生真菌共生体在草地农业系统中的作用

综述了国内外近年对禾草 -内生真菌 (N eotyphodium)的研究进展。全世界现已报道 14种禾草内生真菌 ,与 2 3个属的禾草形成共生体 ,我国已在 13属 2 5种天然草地禾草中发现内生真菌 ,其中发草属 (Descampsia)、大麦属 (H ord eum)和赖草属(L eymus)以往在国际文献中未曾报道。内生真菌在禾草体内产生的生物碱 ,致使采食带菌禾草的马、牛、羊、鹿等家畜产生中毒症状 ,每年给美国、新西兰等国造成的经济损失达 6.4亿美元之多 ,对其毒理研究取得了进展。已发现我国醉马草 (Achnatheruminebrians)对家畜的毒性与内生真菌的侵染有关。内生真菌侵染增加可使禾草对 42种害虫的抗性 ,并可增加对某些线虫和病害的抗性。与不带菌禾草相比 ,带菌禾草的另一特点是抗逆性强 ,牧草产量高。国际在该领域的研究主要集中在多年生黑麦草(L olium p erenne)和高羊茅 (Festuca arundinacea)。我国的研究发现 ,带菌布顿大麦草 (H ordeum bodg anii)和圆柱披碱草(Elymus cylind ricus)的牧草产量分别增加 3 3 .3 %和 2 78.8% ,分孽数分别增加 13 6.8%和 84.5%。目前 ,国际研究的重点包括大规模开展内生真菌生物学与生态学特性的研究 ,创造不含对家畜有害毒素的有益禾草 -内生真菌共生体 ,培育带内生真菌的草坪草品种 ,培育抗毒     

Contribution of fungal loline alkaloids to protection from aphids in a grass-endophyte mutualism

Fungal endophytes provide grasses with enhanced protection from herbivory, drought, and pathogens. The loline alkaloids (saturated 1-aminopyrrolizidines with an oxygen bridge) are fungal metabolites often present in grasses with fungal endophytes of the genera Epichlo? or Neotyphodium. We conducted a Mendelian genetic analysis to test for activity of lolines produced in plants against aphids feeding on those plants. Though most loline-producing endophytes are asexual, we found that a recently described sexual endophyte, Epichlo? festucae, had heritable variation for loline alkaloid expression (Lol+) or nonexpression (Lol-). By analyzing segregation of these phenotypes and of linked DNA polymorphisms in crosses, we identified a single genetic locus controlling loline alkaloid expression in those E. festucae parents. We then tested segregating Lol+ and Lol- full-sibling fungal progeny for their ability to protect host plants from two aphid species, and observed that alkaloid expression cosegregated with activity against these insects. The in planta loline alkaloid levels correlated with levels of anti-aphid activity. These results suggested a key role of the loline alkaloids in protection of host plants from certain aphids, and represent, to our knowledge, the first Mendelian analysis demonstrating how a fungal factor contributes protection to plant-fungus mutualism.     

禾草内生真菌生物碱的研究进展

综述了国内外近20a以来在禾草内生真菌生物碱方面的研究进展。目前,已发现至少4大类10余种生物碱与内生真菌有关。各类生物碱中典型代表物的分子结构已完全清楚,部分内生真菌在离体条件下可产生除黑麦草碱外的生物碱,但产碱量较其在植物体中所产生的低很多,可相差150余倍之多。随着生物技术的发展,美国、新西兰等国在波胺、麦角碱和loline的生物合成途径方面已有了初步的进展,对个别具有重要功能基因以及其所编码的酶已有了深入研究。各种生物碱的致毒机理尚未完全清楚,除饱和吡咯化合物为新陈代谢类毒素和神经性毒素外,其余3类生物碱均为神经性毒素。生物碱可增加禾草对40余种害虫的抗性,并可增加对某些线虫和病害的抗性。诸多因素均可影响寄主植株中生物碱的种类和浓度,包括寄主植株：种群和生态型,植物品种和基因型,植株的部位和生长期;环境：气候因素,土壤养分,季节和年度变化;内生真菌菌株和草地管理利用方式等。用于生物碱检测的主要方法为预分离检测法和直接检测法,其中高效液相色谱法以其分离能力强、选择性高、测定灵敏度高,操作简单,可在室温下进行,应用范围极广的优点而广泛应用。目前,国际关于禾草内生真菌生物碱研究的重点包括创造不含对家畜有毒素的有益禾草-内生真菌共生体,开展基因工程研究以及合理利用生物碱,使其成为新一代的“生物农药”。     

A fungal endophyte reinforces population adaptive differentiation in its host grass species

Hereditary symbioses between fungal endophytes and grasses are relatively recent in the history of plant life. Given < 80 million yr of co-evolution, symbioses are likely to have impacted plant microevolutionary rather than macroevolutionary processes. Therefore, we investigated the microevolutionary role of the fungal endophyte Neotyphodium lolii in the adaptive differentiation of its host species Lolium perenne. Endophyte frequency in 22 natural L. perenne populations was established across a water availability gradient. Adaptive differentiation among five populations, and between symbiotic (S) and nonsymbiotic (NS) plants, was examined in a glasshouse experiment under nonlimiting and limiting water conditions. Genetic differentiation was subsequently assessed among populations, and between S and NS individuals, using 14 simple sequence repeats (SSR). Symbiosis frequencies were positively correlated to water availability. Adaptive population differentiation occurred following a trade-off between biomass production under nonlimiting water conditions and survivorship under water stress. Endophytic symbiosis increased plant survival in xeric populations, and reinforced competitiveness in mesic populations. No genetic difference was detected between S and NS plants within populations. Therefore, we conclude that the endophyte relationship is responsible for these effects. Local adaptation of the host plant, appears to be supported by the fungal endophyte.     

Broad-scale geographic patterns in the distribution of vertically-transmitted, asexual endophytes in four naturally-occurring grasses in Sweden

The presence and distribution of vertically-transmitted, asexual Neotyphodium/Epichloë endophytes in four species of widely distributed grasses, all members of the sub-family Pooideae, were determined at 57 spatially-distinct sites across Sweden in naturally-occurring grass populations. While these endophytes are well-studied in agricultural systems, much less is known about their abundance and distribution in non-agricultural systems at larger scales across landscapes. We used two screening methods to detect endophytes: 1) visual inspection of fixed, stained grass shoots, and 2) immunoblot cards with monoclonal antibodies specific for Neotyphodium / Epichloë endophytes. Infection frequency (i.e. the proportion of individuals) varied widely among species and among sites, a finding common to most studies performed in non-agricultural ecosystems. Festuca rubra had the highest overall infection frequency (23% visual screening, 27% immunoblot screening), while Deschampsia flexuosa (4%) and Poa trivialis (4%) had low frequencies of infection. None of the sampled Agrostis capillaris populations were infected. In F. rubra , the within-site infection frequency varied from 0 to 100%. A significant altitudinal gradient was found for F. rubra , with the infection frequency of the vertically-transmitted endophyte Epichloë festucae decreasing with increasing altitude above sea level. The high variation across and within grass species at different geographical locations that ours and others' studies reveal, agree with suggestions that agronomic model systems cannot be readily extrapolated to understand the ecological role of endophytes in native grasses in the wild. Further investigation into the underlying cause of the observed altitudinal gradient is required to understand broader-scale patterns in the distribution of endophyte-infected grasses.     

Grass-herbivore interactions altered by strains of a native endophyte

Many plants support symbiotic microbes, such as endophytic fungi, that can alter interactions with herbivores. Most endophyte research has focused on agronomically important species, with less known about the ecological roles of native endophytes in native plants. In particular, whether genetic variation among endophyte symbionts affects herbivores of plant hosts remains unresolved for most native endophytes. Here, we investigate the importance of native isolates of the endophyte Epichlo? elymi in affecting herbivory of the native grass host, Elymus hystrix. Experimental fungal isolate-plant genotype combinations and endophyte-free control plants were grown in a common garden and exposed to natural arthropod herbivory. Fungal isolates differed in their effects on two types of herbivory, chewing and scraping. Isolates exhibiting greater sexual reproduction were associated with greater herbivore damage than primarily asexual isolates. Endophyte infection also altered patterns of herbivory within plants, with stroma-bearing tillers experiencing up to 30% greater damage than nonstroma-bearing tillers. Results suggest that intraspecific genetic variation in endophytes, like plant genetic variation, can have important 'bottom-up' effects on herbivores in native systems.     

Do the costs and benefits of fungal endophyte symbiosis vary with light availability?

? Here, we examined whether fungal endophytes modulated host plant responses to light availability. First, we conducted a literature review to evaluate whether natural frequencies of endophyte symbiosis in grasses from shaded habitats were higher than frequencies in grasses occupying more diverse light environments. Then, in a glasshouse experiment, we assessed how four levels of light and the presence of endophyte symbioses affected the growth of six grass species. ? In our literature survey, endophytes were more commonly present in grasses restricted to shaded habitats than in grasses from diverse light environments. ? In the glasshouse, endophyte symbioses did not mediate plant growth in response to light availability. However, in the host grass, Agrostis perennans, symbiotic plants produced 53% more inflorescences than nonsymbiotic plants at the highest level of shade. In addition, under high shade, symbiotic Poa autumnalis invested more in specific leaf area than symbiont-free plants. Finally, shade increased the density of the endophyte in leaf tissues across all six grass species. ? Our results highlight the potential for symbiosis to alter the plasticity of host physiological traits, demonstrate a novel benefit of endophyte symbiosis under shade stress for one host species, and show a positive association between shade-restricted grass species and fungal endophytes.