基于植物内生菌及其次生代谢活性物质多样性的研究

据相关研究表明,植物内生菌属于新型微生物资源,并且种类较多,分布广泛,譬如在最近几年,科学家逐渐发现在植物内生菌中发现了紫杉醇等生物活性物质以及在一些产物中还发现了与次级代谢产物中相同的产物,因此对临床研究具有重要价值和潜在价值。对此研究的主题为:基于植物内生菌及其次生代谢活性物质多样性的研究。本为将从植物内生菌的多样性,植物内生菌次生代谢活性物质的多样性等方面进行逐一研究,现将文章综述如下。     

地衣及其内生真菌活性次级代谢产物研究进展

地衣是一种独特的菌藻共生体,能够在荒漠、高山、冻土等恶劣环境生存,具有特殊的生理结构和独特的生存环境。地衣及其内生真菌能够产生结构新颖、活性广泛的次级代谢产物,研究地衣及其内生真菌次级代谢产物对新型药用资源开发以及利用等方面都具有重要的意义。本文关注了近年来地衣及其内生真菌的次级代谢产物相关研究,并对其生物活性方面的研究成果进行综述。     

一株新的药用植物内生菌Burkholderia sp. H-6

植物内生菌(Plant endophyte)是微生物中的一个重要类群,能参与植物次级代谢产物的合成与转化或独立合成次级代谢产物,其物种丰富,数量庞大,已经成为新医(农)药活性物质的潜在资源.研究显示,目前从植物内生菌中分离出的生物活性物质,大约51%属于未报道过的新化合物.因此,植物内生菌相关领域的研究工作,愈来愈受到国内外同行的关注.     

植物内生微生物及其“暗物质”开发技术的研究进展

植物内生微生物包含内生菌、内生细菌、内生真菌、内生放线菌、内生古细菌等领域,其"暗物质"是指尚未被开发的菌种资源、遗传资源和代谢物资源。根据对宿主植物的作用,可以将内生微生物分为共生内生微生物、有益内生微生物和潜在的病原微生物三类。内生微生物在植物促生、提高植物抗逆性、提高植物的环境适应性、影响植物代谢物合成、参与被污染环境的修复等方面具有广泛的应用。具有生理活性的次级代谢产物的开发和利用是植物内生微生物研究的另一个热门领域,但由于大多数不能被分离培养、次级代谢物的分离分析技术不足等原因,使得大量的植物内生微生物资源仍处于未知状态。表面消毒技术、分离培养技术的改进,"多-组学"技术的联合使用和次级代谢物分离分析技术的发展极大促进了植物内生微生物的研究。在此基础上,开展微生物组研究和多单位多地域的协同研究将会进一步加快植物内生微生物资源的研究、发掘和利用。以上述内容为基础,本文综述了植物内生微生物的功能及其代谢产物研究进展,当前植物内生微生物研究的分离培养方法和组学技术,并在文章最后对该领域的研究方向提出了建议。     

植物内生放线菌多样性及其活性代谢产物的研究进展

植物内生放线菌是一类能与宿主植物长期协同生长且不引起植物感染的特殊微生物。其作为植物内生微生物资源的重要组成部分,不仅分布广泛,资源丰富,绝大部分可产生与宿主植物相同或相似的次生代谢产物,而且这些次级代谢产物往往丰富多样并具有多种生物活性,是寻找和开发新型先导化合物的重要资源,具有重要的研究意义和潜在的应用价值。植物内生放线菌作为一种亟待开发的重要微生物资源,其重要性越来越被研究人员所认同。就近年来国内外关于植物内生放线菌多样性和其次级代谢物抗菌、抗肿瘤、抗氧化和抗虫等生物活性的研究近况进行综述,以期为植物内生放线菌资源的深入研究和应用提供参考。     

珍稀药用植物内生微生物代谢产物研究进展

植物内生微生物代谢产物与宿主植物具有同源性和特异性,即能够产生和宿主相同或相似的次级代谢产物,又可以产生宿主植物本身没有的化合物。本文通过查阅国内外文献,以宿主植物种类为线索,对近年来20种珍稀药用植物内生微生物具有活性的次级代谢产物研究进展做一综述。     

药用植物内生菌对宿主植物促生作用机制研究进展

植物内生菌是一类能够代谢产生新颖生物分子和多种酶类的重要微生物资源,在农业、植保、制药等领域具有广阔的应用前景。了解内生菌与药用植物间相互关系是当前促进药用植物生长和提升药材品质的重要途径。植物内生菌资源具有丰富的多样性,对宿主植物生长发挥着重要功能,如固氮、溶磷、产生铁载体、分泌植物激素吲哚乙酸(indole-3-acetic acid,IAA)、产生ACC脱氨酶(1-aminocyclopropane-1-carboxylate deaminase)、增强宿主抗逆性、产生次生代谢产物等。本文通过相关文献回顾,聚焦内生菌与药用植物间的关系,着重探讨药用植物内生菌对宿主植物的促生作用机制,展望新技术在植物内生菌研究方面的应用,以便有效利用分子手段阐明内生菌对药用植物的促生长作用,为其在相关领域的应用提供理论参考。     

植物内生菌活性代谢产物最新研究进展

内生菌广泛存在于植物组织中,作为一种新型的微生物资源,具有丰富的物种多样性,也是发掘新型天然活性物质的重要途径之一,有些内生菌还能产生与宿主植物相同或相似的活性成分。因此从植物内生菌中挖掘抗菌尤其抗临床耐药菌、抗肿瘤等天然活性产物不仅为新药的研发提供了新的方向,还能在一定程度上解决传统的天然产物药源——药用植物生长缓慢、资源紧缺等问题。从多个角度概述了近年来国内外报道的植物内生菌次生代谢产物及其来源、生物活性等方面的主要成果和最新进展,以期为植物内生菌活性代谢产物的研究提供参考。     

内生菌对植物次生代谢产物的转化

近年研究发现许多药用植物中的活性成分产量低下或副作用大、不利于人体吸收,而内生菌存在于健康植物的组织或器官中,可以对植物次生代谢产物进行转化且具有条件温和、专一有效、收效率高等特点。本文主要对近几年内生菌对植物次生代谢产物转化的研究进行综述和展望,以期为内生菌资源的开发和利用提供参考价值。     

关于植物内生菌的研究

本文从植物内生菌的起源、定义以及分布特点进行分析。依据现阶段内生菌的多样性和分布、运动性、功能、植物修复的研究成果,分析其代谢产物和本身的活性物质在医药领域、农业领域和基因工程领域具有广泛的发展前景。     

Bioactive secondary metabolites produced by microorganisms associated with plants

In the past few decades groups of scientists have focused their study on relatively new microorganisms called endophytes. By definition these microorganisms, mostly fungi and bacteria, colonise the intercellular spaces of the plant tissues. The mutual relationship between endophytic microorganisms and their host plants, taxanomy and ecology of endophytes are being studied. Some of these microorganisms produce bioactive secondary metabolites that may be involved in a host-endophyte relationship. Recently, many endophytic bioactive metabolites, known as well as new substances, possesing a wide variety of biological activities as antibiotic, antitumor, antiinflammatory, antioxidant, etc. have been identified. The microorganisms such as endophytes may be very interesting for biotechnological production of bioactive substances as medicinally important agents. Therefore the aim of this review is to briefly characterize endophytes and summarize the structuraly different bioactive secondary metabolites produced by endophytic microorganisms as well as microbial sources of these metabolites and their host plants.     

Endophytes from wild cereals protect wheat plants from drought by alteration of physiological responses of the plants to water stress

Endophytes contribute to plant performance, especially under harsh conditions. We therefore hypothesized that wild plants have retained beneficial endophytes that are less abundant or not present in related crop plants. To test this hypothesis, we selected two endophytes that were found in Sharon goatgrass, an ancestor of wheat, and tested their effect on bread wheat. Both endophytes infected wheat and improved sustainability and performance under water-limited conditions. To determine how the endophytes modify plant development, we measured parameters of plant growth and physiological status and performed a comparative metabolomics analysis. Endophyte-treated wheat plants had reduced levels of stress damage markers and reduced accumulation of stress-adaptation metabolites. Metabolomics profiling revealed significant differences in the response to water stress of endophyte-treated plants compared with untreated plants. Our results demonstrate the potential of endophytes from wild plants for improvement of related crops and show that the beneficial effects of two endophytes are associated with alteration of physiological responses to water-limited conditions.     

Prospecting potential of endophytes for modulation of biosynthesis of therapeutic bioactive secondary metabolites and plant growth promotion of medicinal and aromatic plants

Medicinal and aromatic plants possess pharmacological properties (antidiabetes, anticancer, antihypertension, anticardiovascular, antileprosy, etc.) because of their potential to synthesize a wide range of therapeutic bioactive secondary metabolites. The concentration of bioactive secondry metabolites depends on plant species, local environment, soil type and internal microbiome. The internal microbiome of medicinal plants plays the crucial role in the production of bioactive secondary metabolites, namely alkaloids, steroids, terpenoids, peptides, polyketones, flavonoids, quinols and phenols. In this review, the host specific secondry metabolites produced by endophytes, their therapeutic properties and host-endophytes interaction in relation to production of bioactive secondry metaboloites and the role of endophytes in enhancing the production of bioactive secondry metabolites is discussed. How biological nitrogen fixation, phosphorus solubilization, micronutrient uptake, phytohormone production, disease suppression, etc. can play a vital role in enhacing the plant growth and development.The role of endophytes in enhancing the plant growth and content of bioactive secondary metabolites in medicinal and aromatic plants in a sustainable mode is highlighted.

     

Endophytic Penicillium species secretes mycophenolic acid that inhibits the growth of phytopathogenic fungi

The worldwide demand for reduced and restricted use of pesticides in agriculture due to serious environmental effects, health risks and the development of pathogen resistance calls for the discovery of new bioactive compounds. In the medical field, antibiotic-resistant microorganisms have become a major threat to man, increasing mortality. Endophytes are endosymbiotic microorganisms that inhabit plant tissues without causing any visible damage to their host. Many endophytes secrete secondary metabolites with biological activity against a broad range of pathogens, making them potential candidates for novel drugs and alternative pesticides of natural origin. We isolated endophytes from wild plants in Israel, focusing on endophytes that secrete secondary metabolites with biological activity. We isolated 302 different endophytes from 30 different wild plants; 70 of them exhibited biological activity against phytopathogens. One biologically active fungal endophyte from the genus Penicillium, isolated from a squill (Urginea maritima) leaf, was further examined. Chloroform-based extraction of its growth medium was similarly active against phytopathogens. High-performance liquid chromatography separation followed by gas chromatography/mass spectrometry analysis revealed a single compound—mycophenolic acid—as the main contributor to the biological activity of the organic extract.     

Fungal endophytes and bioprospecting

Horizontally transmitted fungal endophytes are an ecological group of fungi, mostly belonging to the Ascomycota, that reside in the aerial tissues and roots of plants without inducing any visual symptoms of their presence. These fungi appear to have a capacity to produce an array of secondary metabolites exhibiting a variety of biological activity. Although the ability of fungi to produce unique bioactive metabolites is well known, endophytes have not been exploited, perhaps because we are only beginning to understand their distribution and biology. This review emphasizes the need to routinely include endophytic fungi in the screening of organisms for bioactive metabolites and novel drugs; it also underscores the need to use information obtained concerning fungal secondary metabolite production from other groups of fungi for a targeted screening approach.     

Endophytic Bacteria in Plant Salt Stress Tolerance: Current and Future Prospects

Soil salinity is a major limiting factor for crop productivity worldwide and is continuously increasing owing to climate change. A wide range of studies and practices have been performed to induce salt tolerance mechanisms in plants, but their result in crop improvement has been limited due to lack of time and money. In the current scenario, there is increasing attention towards habitat-imposed plant stress tolerance driven by plant-associated microbes, either rhizospheric and/or endophytic. These microbes play a key role in protecting plants against various environmental stresses. Therefore, the use of plant growth-promoting microbes in agriculture is a low-cost and eco-friendly technology to enhance crop productivity in saline areas. In the present review, the authors describe the functionality of endophytic bacteria and their modes of action to enhance salinity tolerance in plants, with special reference to osmotic and ionic stress management. There is concrete evidence that endophytic bacteria serve host functions, such as improving osmolytes, anti-oxidant and phytohormonal signaling and enhancing plant nutrient uptake efficiency. More research on endophytes has enabled us to gain insights into the mechanism of colonization and their interactions with plants. With this information in mind, the authors tried to solve the following questions: (1) how do benign endophytes ameliorate salt stress in plants? (2) What type of physiological changes incur in plants under salt stress conditions? And (3), what type of determinants produced by endophytes will be helpful in plant growth promotion under salt stress?

     

Induction of abiotic stress tolerance in plants by endophytic microbes

Endophytes are micro‐organisms including bacteria and fungi that survive within healthy plant tissues and promote plant growth under stress. This review focuses on the potential of endophytic microbes that induce abiotic stress tolerance in plants. How endophytes promote plant growth under stressful conditions, like drought and heat, high salinity and poor nutrient availability will be discussed. The molecular mechanisms for increasing stress tolerance in plants by endophytes include induction of plant stress genes as well as biomolecules like reactive oxygen species scavengers. This review may help in the development of biotechnological applications of endophytic microbes in plant growth promotion and crop improvement under abiotic stress conditions.

Significance and Impact of the Study

Increasing human populations demand more crop yield for food security while crop production is adversely affected by abiotic stresses like drought, salinity and high temperature. Development of stress tolerance in plants is a strategy to cope with the negative effects of adverse environmental conditions. Endophytes are well recognized for plant growth promotion and production of natural compounds. The property of endophytes to induce stress tolerance in plants can be applied to increase crop yields. With this review, we intend to promote application of endophytes in biotechnology and genetic engineering for the development of stress‐tolerant plants.     

Endophytic fungi: novel sources of anticancer lead molecules

Cancer is a major killer disease all over the world and more than six million new cases are reported every year. Nature is an attractive source of new therapeutic compounds, as a tremendous chemical diversity is found in millions of species of plants, animals, and microorganisms. Plant-derived compounds have played an important role in the development of several clinically useful anti-cancer agents. These include vinblastine, vincristine, camptothecin, podophyllotoxin, and taxol. Production of a plant-based natural drug is always not up to the desired level. It is produced at a specific developmental stage or under specific environmental condition, stress, or nutrient availability; the plants may be very slow growing taking several years to attain a suitable growth phase for product accumulation and extraction. Considering the limitations associated with the productivity and vulnerability of plant species as sources of novel metabolites, microorganisms serve as the ultimate, readily renewable, and inexhaustible source of novel structures bearing pharmaceutical potential. Endophytes, the microorganisms that reside in the tissues of living plants, are relatively unstudied and offer potential sources of novel natural products for exploitation in medicine, agriculture and the pharmaceutical industry. They develop special mechanisms to penetrate inside the host tissue, residing in mutualistic association and their biotransformation abilities opens a new platform for synthesis of novel secondary metabolites. They produce metabolites to compete with the epiphytes and also with the plant pathogens to maintain a critical balance between fungal virulence and plant defense. It is therefore necessary that the relationship between the plants and endophytes during the accumulation of these secondary metabolites is studied. Insights from such research would provide alternative methods of natural product drug discovery which could be reliable, economical, and environmentally safe.     

Secondary metabolism of pharmaceuticals in the plant in vitro cultures: strategies,approaches, and limitations to achieving higher yield

Biotechnology is playing a vital alternative role in the production of pharmaceutical plant secondary metabolites to support industrial production and mitigate over-exploitation of natural sources. High-value pharmaceuticals that include alkaloids, flavonoids, terpenes, steroids, among others, are biosynthesized as a defensive strategy by plants in response to perturbations under natural environmental conditions. However, they can also be produced using plant cell, tissue, and organ culture techniques through the application of various in vitro approaches and strategies. In the past decades, efforts were on the clonal propagation, biomass and secondary metabolites production in the in vitro cultures of medicinally important plants that produce these molecules. In recent years, the effort has shifted towards optimizing culture conditions for their production through the application of cell line selection, elicitation, precursor feeding, two-phase co-culture among cell, tissue, and organ culture approaches. The efforts are made with the possibility to scale-up the production, meet pharmaceutical industry demand and conserve natural sources of the molecules. Applications of metabolic engineering and production from endophytes are also getting increasing attention but, the approaches are far from practical application in their industrial production.     

Growth,physiological, biochemical and molecular changes in plants induced by magnetic fields: A review

The Earth's geomagnetic field (GMF) is an inescapable environmental factor for plants that affects all growth and yield parameters. Both strong and weak magnetic fields (MF), as compared to the GMF, have specific roles in plant growth and development. MF technology is an eco-friendly technique that does not emit waste or generate harmful radiation, nor require any external power supply, so it can be used in sustainable modern agriculture. Thus, exposure of plants to MF is a potential affordable, reusable and safe practice for enhancing crop productivity by changing physiological and biochemical processes. However, the effect of MF on plant physiological and biochemical processes is not yet well understood. This review describes the effects of altering MF conditions (higher or lower values than the GMF) on physiological and biochemical processes of plants. The current contradictory and inconsistent outcomes from studies on varying effects of MF on plants could be related to species and/or MF exposure time and intensity. The reviewed literature suggests MF have a role in changing physiological processes, such as respiration, photosynthesis, nutrient uptake, water relations and biochemical attributes, including genes involved in ROS, antioxidants, enzymes, proteins and secondary metabolites. MF application might efficiently increase growth and yield of many crops, and as such, should be the focus for future research.