菌根共生体中植物信号物质的产生及其作用机制

菌根是丛枝菌根真菌与宿主植物形成的互利共生体,在共生的不同阶段,植物产生一系列的信号物质如独脚金内酯、溶血磷脂酰胆碱、茉莉酸和水杨酸等.这些信号物质在植物与丛枝菌根真菌间相互识别、菌根形成、营养物质交换,以及植物防御反应诱导等方面发挥重要作用.文中探讨植物信号物质在丛枝菌根共生系统形成前后和病原体侵害的3个阶段可能的生理效应和作用机制,旨在为研究丛枝菌根真菌与植物信号物质的相互作用及其在农业生产和环境保护方面的应用提供依据.     

不同宿主植物对丹参根围土著AM真菌生长发育的影响

利用盆栽实验在灭菌条件下研究了玉米(Zea mays)、葱(Allium fistulosum)、黑麦草(Loliumperenne)和三叶草(Trifolium repens)等4种宿主植物对丹参(Salviamiltiorrhiza)根围土著AM真菌生长和繁殖特性的影响.结果表明,4种供试植物都能与AM真菌形成共生关系,但不同宿主植物形成的菌根特性和程度有明显差异.以三叶草为宿主植物对AM真菌生长最为有利,其根内菌丝SDH活性、孢子数均高于其他3种植物.     

兰科植物与菌根真菌专一性研究进展

为了充分分析兰科(Orchidaceae)植物与菌根真菌专一性关系,以便更好地利用菌根技术实现兰科植物的规模化栽培和野生保育,本文从专一性关系的定义、影响因素、兰科菌根研究方法及共生机制等方面对兰科菌根专一性研究进行了总结和分析.概括出胶膜菌科(Tulasnellaceae)、角担菌科(Ceratobasidiacea...     

AMF对间套作体系中植物-土壤-微生物相互作用的影响及机制

丛枝菌根真菌（AMF）能与自然环境中的多数陆生植物互利共生。间套作种植作为增加农田生态系统生物多样性的重要措施，能显著提高植物对农田环境中多种资源的利用率。在间套作体系中，AMF通过对农作物和土壤环境的影响，提高农田生态系统的经济产量并促进其可持续发展。本文从AMF对宿主植物根系特征的影响、AMF对宿主植物根际微生物群落结构功能的影响、AMF在改善土壤结构提高土壤肥力方面的作用、菌根植物间共生菌丝网络的养分资源传递分配等方面，阐述AMF对间套作体系中植物-土壤-微生物相互作用的影响及其机制，为AMF在农业方面的进一步应用提供理论基础。     

环境胁迫对禾草—内生真菌共生体的影响

Neotyphodium属内生真菌与禾本科植物之间的共生关系因其与农牧业的密切关系而受到研究者们的广泛关注。Neotyphodium属内生真菌长期生活在植物体内的特殊环境中,并与宿主协同进化,在演化过程中二者形成互惠共生关系,一方面内生真菌可从宿主中吸收营养供自己生长需要,另一方面内生真菌可增强宿主植物的抗旱性、抗病性和抗虫性,促进宿主植物生长并提高其竞争能力,但也对家畜产生毒性。     

内生真菌和丛枝菌根真菌提高植物逆境适应性研究进展

内生真菌(endophytic fungi)和丛枝菌根真菌(arbuscular mycorrhiza fungi, AMF)能与绝大多数植物形成互惠共生体,这种共生体中宿主植物为真菌提供其生长繁殖所需的营养物质,真菌则有效促进宿主植物的生长并提高其抗逆性.内生真菌和丛枝菌根真菌在宿主植物抵御生物胁迫和非生物胁迫中所起的作用逐渐引起国内外学者的关注,因此作者综述了内生真菌和丛枝菌根真菌在植物抵御干旱胁迫、盐碱胁迫和重金属胁迫等非生物胁迫以及致病菌和线虫侵染等生物胁迫中的作用,以使读者能及时并全面地了解这一领域的研究动态.     

植食性昆虫、植物和共生微生物的功能关联（英文）

植食性昆虫和植物均能与微生物形成密切关系,它们各自的生态功能及相互关系也常被共生微生物所影响。近年来,随着分子水平研究方法的进展,植食性昆虫和植物中很多可遗传共生微生物(细菌、真菌等)被发现。共生微生物能够在营养、生殖、防御和解毒等方面给宿主带来显著影响,并与宿主形成竞争、互利或寄生等关系。植食性昆虫体内的含菌胞、肠道、血淋巴、唾液腺等常含有重要功能的共生微生物。新的分子生物学手段和高通量测序技术的应用使得我们能够增加对宿主和共生微生物(即使处于低丰度)之间关系的了解。尝试总结植食性昆虫和植物共生微生物的多样性及其关系、昆虫和植物互作机制、昆虫共生菌解毒植物毒素等方面的研究,突出强调应以系统观思维来理解共生微生物、植食性昆虫和植物间的功能关联,就将来值得研究的问题提出了建议。     

丛枝菌根的生理生态功能

丛枝菌根是自然界分布最广泛的一种菌根,它是由专性营养共生的丛枝菌根真菌和大部分陆生植物所形成的互惠共生体,具有重要的生理生态功能.通过对丛枝菌根与植物的营养吸收、抗逆抗病以及丛枝菌根与植物群落和生态系统之间的重要关系进行综述,从而说明AMF在植被群落的建立和演替等方面具有重要作用.     

菌根真菌对有机氮吸收利用的研究进展

综述了菌根真菌对有机氮的吸收利用在植物生理学、分子水平及实验装置方面国内外近年来取得的一些研究成果.菌根真菌吸收有机氮后能向宿主植物转运,其中丛枝菌根真菌吸收氨基氮后在根外菌丝中合成载体———精氨酸(Arg),它既能在根外菌丝(ERM)和根内菌丝(IRM)间双向运转,又能在根内菌丝中经尿素循环分解成NH4+,作为氮源整合入根内菌丝中的其他氨基酸或通过NH4+-转运蛋白转运给宿主植物.已经从菌根真菌中克隆出或检测到表达一些与氮代谢相关的基因.与研究需求相适应的实验装置也在不断发展.     

丛枝菌根真菌对氮素的吸收作用和机制

丛枝菌根真菌可以与绝大多数陆生植物共生,它可以吸收铵态氮、硝态氮、一些氨基酸和一些复杂的有机氮素,吸收的氮素在根外菌丝中转化成精氨酸,并以这种形式运输到根内菌丝,在根内菌丝和根细胞界面,精氨酸再进一步转化为NH4^＋后转移到宿主植物体,参与植物氮素代谢,而转移的氮量及对宿主植物氮营养的贡献与宿主植物、真菌以及基质养分和水分条件有关．     

丛枝菌根真菌在农业中的应用：研究进展与挑战

 丛枝菌根（arbuscular mycorrhiza，AM）真菌能够和大多数农作物形成互利共生体系，有效改善作物矿质营养，减轻环境胁迫对作物生长的不利影响，提高作物产量和品质。由于AM真菌的功能多面性，其在农业生产中具有潜在重要作用和广阔应用前景。结合AM真菌农业应用技术途径和适用情景，讨论了作物种植制度和管理措施对AM真菌功能的影响及可能的调控途径，分析了菌根技术发展趋势及面临的机遇和挑战，提出加强AM真菌功能多面性及其应用途径优化研究，将有助于促进AM真菌菌剂相关产业的发展以及AM真菌在农业生产中的广泛应用。     

Nitrogen transfer in the arbuscular mycorrhizal symbiosis

Most land plants are symbiotic with arbuscular mycorrhizal fungi (AMF), which take up mineral nutrients from the soil and exchange them with plants for photosynthetically fixed carbon. This exchange is a significant factor in global nutrient cycles as well as in the ecology, evolution and physiology of plants. Despite its importance as a nutrient, very little is known about how AMF take up nitrogen and transfer it to their host plants. Here we report the results of stable isotope labelling experiments showing that inorganic nitrogen taken up by the fungus outside the roots is incorporated into amino acids, translocated from the extraradical to the intraradical mycelium as arginine, but transferred to the plant without carbon. Consistent with this mechanism, the genes of primary nitrogen assimilation are preferentially expressed in the extraradical tissues, whereas genes associated with arginine breakdown are more highly expressed in the intraradical mycelium. Strong changes in the expression of these genes in response to nitrogen availability and form also support the operation of this novel metabolic pathway in the arbuscular mycorrhizal symbiosis.     

Characterization of a carbohydrate transporter from symbiotic glomeromycotan fungi

The symbiotic relationships between mycorrhizal fungi and plants have an enormous impact on terrestrial ecosystems. Most common are the arbuscular mycorrhizas, formed by fungi belonging to the phylum Glomeromycota. Arbuscular mycorrhizal fungi facilitate the uptake of soil nutrients by plants and in exchange obtain carbohydrates, thus representing a large sink for atmospheric plant-fixed CO(2). However, how carbohydrates are transported through the symbiotic interface is still unknown. Here we report the characterization of the first known glomeromycotan monosaccharide transporter, GpMST1, by exploiting the unique symbiosis of a glomeromycotan fungus (Geosiphon pyriformis) with cyanobacteria. The GpMST1 gene has a very low GC content and contains six introns with unusual boundaries. GpMST1 possesses twelve predicted transmembrane domains and functions as a proton co-transporter with highest affinity for glucose, then mannose, galactose and fructose. It belongs to an as yet uncharacterized phylogenetic monosaccharide transporter clade. This initial characterization of a new transporter family involved in fungal symbiosis will lead to a better understanding of carbon flows in terrestrial environments.     

Plant recognition of symbiotic bacteria requires two LysM receptor-like kinases

Although most higher plants establish a symbiosis with arbuscular mycorrhizal fungi, symbiotic nitrogen fixation with rhizobia is a salient feature of legumes. Despite this host range difference, mycorrhizal and rhizobial invasion shares a common plant-specified genetic programme controlling the early host interaction. One feature distinguishing legumes is their ability to perceive rhizobial-specific signal molecules. We describe here two LysM-type serine/threonine receptor kinase genes, NFR1 and NFR5, enabling the model legume Lotus japonicus to recognize its bacterial microsymbiont Mesorhizobium loti. The extracellular domains of the two transmembrane kinases resemble LysM domains of peptidoglycan- and chitin-binding proteins, suggesting that they may be involved directly in perception of the rhizobial lipochitin-oligosaccharide signal. We show that NFR1 and NFR5 are required for the earliest physiological and cellular responses to this lipochitin-oligosaccharide signal, and demonstrate their role in the mechanism establishing susceptibility of the legume root for bacterial infection.     

Plant sesquiterpenes induce hyphal branching in arbuscular mycorrhizal fungi

Arbuscular mycorrhizal (AM) fungi form mutualistic, symbiotic associations with the roots of more than 80% of land plants. The fungi are incapable of completing their life cycle in the absence of a host root. Their spores can germinate and grow in the absence of a host, but their hyphal growth is very limited. Little is known about the molecular mechanisms that govern signalling and recognition between AM fungi and their host plants. In one of the first stages of host recognition, the hyphae of AM fungi show extensive branching in the vicinity of host roots before formation of the appressorium, the structure used to penetrate the plant root. Host roots are known to release signalling molecules that trigger hyphal branching, but these branching factors have not been isolated. Here we have isolated a branching factor from the root exudates of Lotus japonicus and used spectroscopic analysis and chemical synthesis to identify it as a strigolactone, 5-deoxy-strigol. Strigolactones are a group of sesquiterpene lactones, previously isolated as seed-germination stimulants for the parasitic weeds Striga and Orobanche. The natural strigolactones 5-deoxy-strigol, sorgolactone and strigol, and a synthetic analogue, GR24, induced extensive hyphal branching in germinating spores of the AM fungus Gigaspora margarita at very low concentrations.     

几种野生花卉丛枝菌根发育状况的研究

丛枝菌根是自然界中,植物与真菌形成的分布最广泛的一类互惠共生体。作者对山东省的6种重要野生花卉小黄花菜(Hemerocallis minorMill.)、萱草(Hemerocallis fulvaL.)、琥珀千里光(Senecio ambraceusTurcz.)、矮鸢尾(Iris chamaeiris)、甘野菊(Dendranthema lavandulaefolium)、锦鸡儿(Catagana sinicaRehd.)的AM真菌的侵染状况、典型结构的发育状况以及其根际土壤中AM真菌的孢子密度和根际AM真菌的相对多度和频度进行了研究。结果表明,所调查的6种野生花卉都被AM真菌侵染,且可观察到典型结构泡囊,其根际土壤中AM真菌孢子密度也相当丰富。在本次调查中共分离到了5个属的AM真菌,其中无梗囊霉属和球囊霉属真菌是野生花卉根际AM真菌的优势类群。     

A plant receptor-like kinase required for both bacterial and fungal symbiosis

Most higher plant species can enter a root symbiosis with arbuscular mycorrhizal fungi, in which plant carbon is traded for fungal phosphate. This is an ancient symbiosis, which has been detected in fossils of early land plants. In contrast, the nitrogen-fixing root nodule symbioses of plants with bacteria evolved more recently, and are phylogenetically restricted to the rosid I clade of plants. Both symbioses rely on partially overlapping genetic programmes. We have identified the molecular basis for this convergence by cloning orthologous SYMRK ('symbiosis receptor-like kinase') genes from Lotus and pea, which are required for both fungal and bacterial recognition. SYMRK is predicted to have a signal peptide, an extracellular domain comprising leucine-rich repeats, a transmembrane and an intracellular protein kinase domain. Lotus SYMRK is required for a symbiotic signal transduction pathway leading from the perception of microbial signal molecules to rapid symbiosis-related gene activation. The perception of symbiotic fungi and bacteria is mediated by at least one common signalling component, which could have been recruited during the evolution of root nodule symbioses from the already existing arbuscular mycorrhiza symbiosis.     

菌丝内生细菌及其宿主真菌共生体系研究进展

微生物共生普遍存在于自然界中，真菌-细菌联合体能以多种方式相互作用，共同发挥各种生态功能。有些细菌驻留在真菌菌丝内部，借以调控真菌的生长、发育、分布和次级代谢过程，这些细菌被称为菌丝内生细菌（endohyphal bacteria, EHB）。EHB的研究揭开了微生物生态学的一个新篇章，是真菌与细菌共生关系中最紧密的代表。在逆境条件下，EHB可以调节寄主生殖机制相关的关键成分或步骤，诱导植物激素类物质的产生，对寄主真菌具有辅助性保护作用。研究最深入的真菌-EHB共生体系是植物致病性根霉菌Rhizopus sp.与伯克霍尔德氏菌Burkholderia sp.，引起水稻幼苗枯萎病所必需的植物毒素——根霉素是由伯克霍尔德氏菌所产生的，而非寄主根霉菌本身产生的。EHB也会影响定殖于高等植物的内生真菌的生态和多样性。在某些情况下，EHB还有助于激活参与识别、转录调节和初级代谢蛋白合成过程的相关基因。目前已开发出了无菌培养分离EHB的方法，然而对真菌-EHB共生体系的研究尚不够深入。综述了菌丝内生细菌EHB及其与宿主真菌的共生体系，阐述这些伴侣之间复杂微妙的相互关系，以及EHB对宿主真菌和宿主植物生长和发育的影响，并对该领域的研究方向提出了建议。