植物内生菌定殖检测技术及其应用

自然环境中内生菌定殖于植物体内,对宿主植物产生多种有益效应,但是内生菌定殖情况难以检测,相关研究不够深入系统。目前在该领域使用较为广泛的检测技术包括：荧光标记、抗生素标记、荧光定量PCR和高通量测序等。内生菌通过孔隙伤口和降解细胞壁等方式侵染植物,通过种子垂直传递核心内生菌。对植物内生菌定殖的侵染方式、定殖方法和检测技术进行了归纳和整理,介绍了内生菌多种侵染和迁移途径,总结了目前内生菌定殖在生物防治、促进植物生长和污染修复等方面的功能,综述了多种检测方式在应用中的特点,以期为内生菌定殖植物的相关研究及其应用提供参考依据。     

内生菌对提高植物抗盐碱性的研究进展

土壤盐碱化是制约我国农作物产量的主要因素之一。如何增强农作物的抗盐碱特性,已成为我国农业持续高效发展的重大课题。植物内生菌存在于植物内部,在增强植物抗病、抗虫、抗旱等胁迫能力方面具有一定作用。内生菌与植物共生关系对植物的显著影响这一现象引起了国内外学者的广泛关注。主要综述植物内生菌的多样性,并从植物的ROS清除系统、细胞中渗透调节物质、矿质元素吸收以及光合作用等方面来说明内生菌对植物耐盐碱能力的影响。     

植物内生菌群落组成及其功能研究进展

植物内生菌是栖居在植物组织内部、以宿主植物代谢物为营养物质的一类微生物。植物内生菌种类丰富,并通过不同的方式定殖在植物体内,与宿主植物互利共生。植物内生菌促进植物的生长发育,通过增强营养物质吸收、与病原菌竞争生态位、在代谢过程中产生抗菌物质以及诱导宿主植物产生抗性等机制,提高宿主植物的抗逆性,并且其群落的组成因生态环境、寄主植物不同部位、生长周期的不同发育阶段而显著不同。人们利用传统组织分离法、高通量测序法以及人工重组生物群落等研究方法对植物与内生菌相互作用进行了深入的研究。本文对植物内生菌群落的组成、内生菌对宿主植物影响的功能研究以及人工内生菌群的构建进行重点阐述,以期为植物内生菌的开发和利用奠定坚实基础。     

两种不同生境中国沙棘种子内生细菌的多样性

植物内生菌广泛分布于植物的各种组织及器官中,对植物的生长表现出各种作用,而植物种子中的内生菌对植物的作用也越来越受到人们的关注。以榆中县和秦安县两种不同生境的中国沙棘种子为材料,分析中国沙棘种子内生细菌多样性,以期探究生境对种子内生菌多样性的影响,并为进一步研究种子内生菌与沙棘的相互作用提供依据。研究利用纯培养方法和高通量测序方法分别进行中国沙棘种子内生细菌多样性分析。对纯培养分离得到的内生细菌,利用16S rRNA基因序列分析法结合形态学特征进行内生细菌的鉴定;对高通量测序得到的数据进行基于OTUs(Operational Taxonomic units,可操作分类单元)的物种注释分析。通过纯培养方法从榆中县中国沙棘种子中分离得到4株内生细菌,分属于芽孢杆菌属(Bacillus)、葡萄球菌属(Staphylococcus)和假单胞菌属(Pseudomonas);秦安县中国沙棘种子中分离得到5株内生细菌,分属于芽孢杆菌属(Bacillus)、葡萄球菌属(Staphylococcus)和不动杆菌属(Acinetobacter)。采用高通量测序方法检测到榆中县中国沙棘种子内生细菌分属于7个门、68个属,秦安县中国沙棘种子内生细菌分属于5个门、30个属。在门分类水平,榆中县中国沙棘种子内生细菌的主要优势门类是蓝藻门(Cyanobacteria)和变形菌门(Proteobacteria),相对丰度分别为95.62%和2.03%;秦安县中国沙棘种子的主要优势门类是变形菌门(Proteobacteria)和蓝藻门(Cyanobacteria),相对丰度分别为91.68%和8.06%。在属分类水平,榆中县中国沙棘种子内生细菌的优势菌属为蓝藻细菌属(Cyanobacteria),相对丰度为95.09%;秦安县中国沙棘种子内生细菌的优势菌属为寡养单胞菌属(Stenotrophomonas),相对丰度为85.60%。榆中县和秦安县两种不同生境中国沙棘种子内生细菌有着丰富的多样性,且内生细菌的多样性和丰富度存在明显差异,表现为榆中县中国沙棘种子内生细菌的多样性和丰富度均高于秦安县中国沙棘种子内生细菌。     

林下参内生生防细菌的分离鉴定及定殖能力

【背景】多年生林下参在自然环境下生长多年,其体内存在的内生菌具有更强的适应性和定殖性,可以提高植物自身抗性,抑制病原菌的生长,更好地发挥与植物的互作。【目的】筛选定殖能力强、繁殖能力快且对病原菌具有拮抗作用的优势菌株。【方法】采用常规组织分离方法,从健康林下参根部组织中分离内生菌,通过对峙试验筛选出对人参病原菌有拮抗作用的内生细菌并对其以传统的鉴定方法进行鉴定。【结果】在得到的6株内生细菌中,菌株LXS-N2对人参立枯病病原菌、人参猝倒病病原菌均有明显抑菌性,而且具有定殖性好、繁殖快的特点,通过破坏病原真菌细胞壁和细胞膜以及改变菌丝形态从而抑制病原真菌生长。【结论】经形态学观察、生理生化反应及16S rRNA基因序列分析鉴定内生菌LXS-N2为贝莱斯芽孢杆菌,具有良好的应用开发潜力。     

植物内生细菌的侵染定殖规律研究进展

详细综述了植物内生细菌的侵染定殖过程,即吸附、侵入、定殖三个阶段。着重阐述了对植物内生细菌的定殖检测方法,包括抗生素标记法、免疫学方法、基因标记法及特异性寡核苷酸片段标记法等。另外,对植物内生细菌的来源及定殖影响因子也进行了系统讨论,并对未来植物内生细菌定殖研究前景作了展望。     

植物内生菌在生物防治中的应用

从植物内生菌的抗病虫机理及生防作用方面综述了植物内生菌在生物防治中的研究进展,对植物内生菌的抗病虫机理进行了探讨,并展望了植物内生菌在植物保护中的应用前景.     

植物内生细菌的研究

植物内生细菌是能够定殖在植物细胞间隙或细胞内,并与寄主植物建立和谐联合关系的一类微生物I’］。自本世纪初开始,人们不断地从植物的根、叶、甚至茎和种子上分离并鉴定出多种微生物,但其在寄主植物中的生物学作用却未能引起研究者的重视。近年来,由于一些研究结果表明内生细菌能够作为外源基因的载体,又具有植物保护剂的功能,可以产生植物促生物质或可作为联合固氮菌剂,由此有关内生细菌的研究才引起植物学家和微生物学家的兴趣。l植物内生细菌的研究现状有关植物内生细菌的研究主要涉及两方面的内容：（l）生态学研究：内生细菌…     

内生菌协同宿主植物修复土壤复合污染的研究进展

土壤复合污染日益严重,危及植物生长及人类发展,寻找修复土壤复合污染的有效方法已经成为环境领域的优先事项。复合污染指同一环境中存在两种或两种以上的污染物,分为复合重金属污染、复合有机污染物污染及重金属-有机污染物复合污染。近些年发现内生菌能定殖在植物中,并且被感染的植物不会引起任何外在病症,其主要通过促进宿主植物生长,改变植物摄取污染物能力和酶促降解污染物等方法增强植物修复能力。本文综述了具有复合重金属和复合有机污染抗性的内生菌种类及其作用机制,并展望了内生菌协同宿主植物修复环境中复合污染物的研究方向。     

植物内生细菌的分离、分类、定殖与应用

植物内生细菌已成为国内外的研究热点,目前已从植物中分离得到许多不同种属的植物内生细菌,其中有的具有促生与防治病害等对宿主植物有利的作用,而一些则具有潜在的致病性。研究人员利用多种方法对植物内生细菌的内生定殖行为进行研究,发现了有意义的定殖规律,例如,某种植物内生细菌对其宿主的侵染能力明显强于另一种内生细菌。目前,尽管植物内生细菌还有不少问题有待解决,但它在农业上的巨大应用潜力业已彰显。     

Fungal endophytes intrinsically associated with micropropagated plants regenerated from native <Emphasis Type="Italic">Bouteloua eriopoda</Emphasis> Torr. and <Emphasis Type="Italic">Atriplex canescens</Emphasis> (Pursh) Nutt.

Summary Black grama (Bouteloua eriopoda) and fourwing saltbush (Atriplex canescens) are important grass and shrub species in arid rangelands of the northern Chihuahuan Desert. They are naturally colonized by dark septate endophytic fungi that cannot be eliminated by seed disinfestation. Plants were regenerated from both species and appeared to be fungus-free in axenic cultures. Analysis of callus and regenerated plants of both species using dual staining with light and scanning electron microscopy revealed fungal endophytes intrinsically associated with cells, roots and leaves of regenerated plants that are also associated with native plants. Fungal layers and biofilms prevent direct exposure of callus, root or leaf tissues to the external environment. Micropropagation is a valuable tool for identifying key fungal endophytes that enhance drought tolerance in native desert plants.     

Maize seed endophytes

Maize is a vital global crop, and each seed (kernel) hosts an ecosystem of microbes living inside it. However, we know very little about these endophytes and what their role is in plant production and physiology. In this Microreview, I summarize the major questions around maize seed endophytes, including what organisms are present, how they get there, whether and how they transmit across generations, and how they and the plant affect each other. Although several studies touch on each of these areas, ultimately there are far more questions than answers. Future priorities for research on maize seed endophytes should include understanding what adaptations allow microbes to be seed endophytes, how the host genetics and the environment affect these communities, and how maize seed endophytes ultimately contribute to the next generation of plants.     

Bacterial Endophytes: Potential Role in Developing Sustainable Systems of Crop Production

Most healthy naturally propagated plants grown in field or potting soils are colonized by communities of endophytic bacteria, embracing a wide variety of species and genera. These bacteria form nonpathogenic relationships with their hosts: some beneficial, some neutral, and some detrimental. Such associations can increase plant growth and hasten development or improve resistance to environmental stress. Endophytic bacteria have been implicated in supplying biologically fixed nitrogen in non-legumes, and these associations can increase the nitrogen economy of a crop, reducing the requirement for N fertilizers. Bacterial endophytes have also been shown to prevent disease development through endophyte-mediated de novo synthesis of structural compounds and fungitoxic metabolites. Such induced protection responses have been linked to certain forms of systemic acquired (disease) resistance. Certain crop sequences have been shown to favor the build-up of specific plant growth-promoting bacterial endophyte populations. These can lead to the creation of beneficial host-endophyte allelopa-thies, with implications for the formation and maintenance of fertile, disease-suppressive soils. Manipulating bacterial populations in soils and within crops will be crucial if endophytes are to be utilized in crop production systems, and special techniques will be required to do so. This review surveys the natural associations between bacterial endophytes and their hosts, and discusses how such relationships can be employed most productively in sustainable systems of agricultural crop production.     

Seed predation as a barrier to alien conifer invasions

Interactions between exotic plants and animals can play a major role in determining success or failure of plant introductions. Seed predation has been seen as important in explaining biotic resistance to plant invasion, but this hypothesis has rarely been tested. We studied seed predation on exotic forest plants on an island in Patagonia, Argentina where 43 pine species, including 60% of the world’s known invasive Pinaceae, were introduced ca. 80 years ago, but where exotics attain relatively high densities only near the original plantings. To test if seed predation limits exotic conifer establishment in this area, we compared seed predation in areas close to plantations (colonized by exotics) and far from them (not invaded). Seeds of exotics were preferred over seeds of native species, possibly because exotic seeds are bigger. Predation was more intense in areas far from plantations than in areas close to them, substantially reducing the chances of exotic seed establishment. Using automatic cameras, we found that both rodents and birds preyed on exotic seeds. This study suggests that native seed predators can be an important component of biological resistance to plant invasion.     

Endophytic fungal diversity of 2 sand dune wild legumes from the southwest coast of India

Endophytic fungi of 3 age classes (seeds, seedlings, and mature plants) and 5 tissue classes (cotyledons, seed coats, roots, stems, and leaves) of coastal sand dune legumes Canavalia cathartica and Canavalia maritima were assessed by plating surface-sterilized segments on malt extract agar. Forty-six fungal taxa comprising 6 ascomycetes, 33 mitosporic fungi, 2 zygomycetes, and 5 sterile morphospecies were recovered. There was no significant difference in the colonization frequency of endophytes between plant species (p = 0.4098, Student's t test). Among the age classes, endophytic fungi colonized over 90% of seedlings and mature plants. Similarly, among tissue classes, endophytic fungi colonized over 90% of root, stem, and leaf segments. Diversity and richness of endophytic fungi were higher in C. cathartica than in C. maritima. Rarefaction curves revealed a "higher expected number of species" in mature plants of C. cathartica and seedlings of C. maritima, whereas it was highest in leaves of both plant species. The most dominant endophyte, Chaetomium globosum, colonized over 50% of the root, stem, and leaf segments of C. maritima and over 50% of the root segments of C. cathartica. The colonization frequency of C. globosum was found to be 5%-12.5% in seeds and increased up to 40%-64.4% in seedlings or mature plants. Halosarpheia sp. was the only marine fungus recovered among the endophytes.     

The plant hormone salicylic acid interacts with the mechanism of anti‐herbivory conferred by fungal endophytes in grasses

The plant hormone salicylic acid (SA) is recognized as an effective defence against biotrophic pathogens, but its role as regulator of beneficial plant symbionts has received little attention. We studied the relationship between the SA hormone and leaf fungal endophytes on herbivore defences in symbiotic grasses. We hypothesize that the SA exposure suppresses the endophyte reducing the fungal‐produced alkaloids. Because of the role that alkaloids play in anti‐herbivore defences, any reduction in their production should make host plants more susceptible to herbivores. Lolium multiflorum plants symbiotic and nonsymbiotic with the endophyte Epichloë occultans were exposed to SA followed by a challenge with the aphid Rhopalosiphum padi. We measured the level of plant resistance to aphids, and the defences conferred by endophytes and host plants. Symbiotic plants had lower concentrations of SA than did the nonsymbiotic counterparts. Consistent with our prediction, the hormonal treatment reduced the concentration of loline alkaloids (i.e., N‐formyllolines and N‐acetylnorlolines) and consequently decreased the endophyte‐conferred resistance against aphids. Our study highlights the importance of the interaction between the plant immune system and endophytes for the stability of the defensive mutualism. Our results indicate that the SA plays a critical role in regulating the endophyte‐conferred resistance against herbivores.     

Endophytes from Argemone mexicana and Datura metel activate induced-systemic resistance in multiple hosts and show host- and pathogen-specific protection

Endophytes are known to activate induced systemic resistance (ISR) in plants. However, detailed studies regarding the location, host, and pathogen specificity are limited. To investigate the influence of the source of endophytes on ISR, we collected Argemone mexicana and Datura metel plants from two different locations in northeast India. We isolated endophytes from these plants and tested their ability to confer ISR-mediated protection. We found that endophytes from D. metel from both locations activated ISR in D. metel plants. However, endophytes from A. mexicana from only one place triggered ISR in A. mexicana. We also observed cross-protection by the endophytes from these plants in Arabidopsis thaliana in a host- and pathogen-specific manner. The results altogether demonstrated that endophytes found in plants under the natural environment play a significant role in generating broad-spectrum resistance against soil microbes. These endophytes might be selectively used to induce ISR in plants.

     

烟草内生菌资源及其应用研究进展

烟草内生菌广泛分布于烟草根、茎、叶及种子中,具有丰富的生物多样性。研究发现感染内生菌的烟草往往具有生长迅速、抗病虫害能力强、亚硝胺类物质含量低等优势,总体上具有更强的生存竞争力和更优的品质。本文综述了烟草内生菌资源概况及其在烟草栽培中的重要作用,总结了内生菌作用机制。最后,探讨了当前烟草内生菌应用中存在的问题,并对其应用前景进行了展望。     

Mycobiota diversity and its vertical transmission in plants along an elevation gradient in mountains

Plants are colonized by fungal endophytes. In this study we tested the hypothesis that endophyte communities in mountain plants changes along the elevation gradient. We identified fungal endophytes in aboveground parts and seeds of five plant species at altitudes of 1000–1750 m in the Tatra National Park. Endophytes isolated from them were grouped into morphotypes on the basis of macroscopic features, such as mycelium shape and colour. Isolates representing individual morphotypes were identified using molecular markers ITS1 and ITS2. When comparing species composition, we used Bray-Curtis distance matrices, calculated on the basis of frequency of the given fungal species. We identified 16 species of fungal endophytes. Five taxa were absent from seeds in spite of their occurrence in mother plant leaves. Differences in altitude were not significantly correlated with fungal species composition observed at a given sampling site. There was also no significant correlation between the species composition of leaf and seed mycobiota. This suggests imperfect vertical transmission in the studied plant species.     

The plant endosphere world – bacterial life within plants

The plant endosphere is colonized by complex microbial communities and microorganisms, which colonize the plant interior at least part of their lifetime and are termed endophytes. Their functions range from mutualism to pathogenicity. All plant organs and tissues are generally colonized by bacterial endophytes and their diversity and composition depend on the plant, the plant organ and its physiological conditions, the plant growth stage as well as on the environment. Plant-associated microorganisms, and in particular endophytes, have lately received high attention, because of the increasing awareness of the importance of host-associated microbiota for the functioning and performance of their host. Some endophyte functions are known from mostly lab assays, genome prediction and few metagenome analyses; however, we have limited understanding on in planta activities, particularly considering the diversity of micro-environments and the dynamics of conditions. In our review, we present recent findings on endosphere environments, their physiological conditions and endophyte colonization. Furthermore, we discuss microbial functions, the interaction between endophytes and plants as well as methodological limitations of endophyte research. We also provide an outlook on needs of future research to improve our understanding on the role of microbiota colonizing the endosphere on plant traits and ecosystem functioning.