丛枝菌根真菌影响作物非生物胁迫耐受性的研究进展

土壤中存在着大量不同种类的微生物资源,土壤微生物能够与自然界中的大多数植物密切合作,其中丛枝菌根真菌(arbuscular mycorrhizal fungi,AMF)起着十分重要的作用。近年来,对于AMF的研究越来越多。AMF是存在于土壤中的重要真菌之一,是土壤中的菌根真菌菌丝与高等植物营养根系形成的一种联合体。AMF可以与陆地上90%左右的植物根系形成共生体,通过在植物根系形成重要的“丛枝菌根”结构而为植物提供更多的养分。为了了解接种AMF对作物生长过程中耐受一些非生物胁迫(如干旱、极端温度、重金属污染、盐分、不利的土壤pH变化等)性能方面的影响,基于之前接种AMF对养分胁迫下玉米生长影响的研究,在扩大作物品种的基础上,通过查阅大量文献,结合试验研究及对前人和近年来关于AMF的一些最新研究进展,获得了具有实践性意义的新发现：AMF与植物共生有助于植物生长,可以改善植物的营养状况,并且可以保护植物免受各种非生物环境胁迫的影响。由此可以得出结论：AMF通过各种机制改善植物生长状况,提高作物抗逆性,为作物增产、农民增收创造了福利,并且避免了由于肥料过量施用导致的一些污染环境问题。本文主要综述了接种AMF在各种非生物环境胁迫(干旱、极端温度、重金属污染、盐分、不利的土壤pH变化等)条件下对植株生长和发育的有利影响,并对目前存在的不足和今后研究的重点提出几点建议。     

Endophytic Cephalotheca sulfurea AGH07 reprograms soybean to higher growth

Abstract

Gibberellins (GAs) are well known for plant growth promotion. GAs production by fungi has received little attention, although substantial work has been carried out on other aspects of plant growth-promoting fungi (PGPF). We investigated GAs production and plant growth-promoting capacity of an endophytic fungus isolated from the roots of soil grown soybean plants. The endophytic fungus is reported as GAs producer and as PGPF for the first time in this study. Nine endophytic isolates were collected from the roots of soybean, and culture filtrates (CFs) obtained from their pure cultures were screened on Waito-C, a dwarf rice cultivar, for the presence of GAs. Of these, seven fungal isolates promoted shoot length as compared to control (distilled water), while one inhibited it. Three fungal isolates were selected on the basis of higher shoot elongation as compared to wild type Gibberella fujikuroi, which was used as positive control. The growth-prompting capacity of selected fungal isolates SB5-1, SB3-2, and SB3-3 was bio-assayed on soybean cv. Hwangkeumkong. Fungal isolate SB5-1 provided maximum plant height (31.6 cm), shoot length (21.1 cm), whole plant fresh biomass (2.41 g), shoot fresh biomass (1.99 g), and leaf area (24.37 cm²). The CF of isolate SB5-1 was analyzed for the presence of GAs, and it was found that all physiologically active GAs were present (GA₁, 0.15 ng/ml, GA₃, 1.2 ng/ml, GA₄, 7.37 ng/ml, and GA₇, 3.18 ng/ml) in conjunction with physiologically inactive GA₅, GA₉, GA₁₅, GA₁₉, GA₂₀, and GA₂₄. The fungal isolate SB5-1 was identified as a new strain of Cephalotheca sulfurea through molecular and phylogenetic approaches.     

Progress and challenges for abiotic stress proteomics of crop plants

Plants are continually challenged to recognize and respond to adverse changes in their environment to avoid detrimental effects on growth and development. Understanding the mechanisms that crop plants employ to resist and tolerate abiotic stress is of considerable interest for designing agriculture breeding strategies to ensure sustainable productivity. The application of proteomics technologies to advance our knowledge in crop plant abiotic stress tolerance has increased dramatically in the past few years as evidenced by the large amount of publications in this area. This is attributed to advances in various technology platforms associated with MS‐based techniques as well as the accessibility of proteomics units to a wider plant research community. This review summarizes the work which has been reported for major crop plants and evaluates the findings in context of the approaches that are widely employed with the aim to encourage broadening the strategies used to increase coverage of the proteome     

Endophytic fungi alter relationships between diversity and ecosystem properties

Recent studies have expanded research on biodiversity by investigating whether the effects of diversity on ecosystem functioning hinge on the presence of symbiotic microorganisms. Cool‐season grasses commonly harbour endophytic fungi that can enhance plant resistance to herbivory, drought and competition. We address whether these endosymbionts modify relationships between diversity and two ecosystem properties: productivity and invasibility. We develop a graphical model that predicts endophyte infection of a grass host will weaken correlations between diversity and ecosystem properties. We then use a long‐term field experiment to test this prediction by manipulating symbiosis in tall fescue grass (Festuca arundinacea), a common and invasive species in the US. As predicted, endophyte infection reduced the strength of correlations between diversity and both primary productivity and the invasiveness of tall fescue. By altering relationships between diversity and ecosystem functioning, endophytic fungi may contribute more to the dynamics of communities than previously supposed.     

Endophytic bacteria (Sphingomonas sp. LK11) and gibberellin can improve Solanum lycopersicum growth and oxidative stress under salinity

This study aims to understand the effects of salinity on the growth and oxidative stress enzymes of endophytic bacteria (Sphingomonas sp. LK11) and tomato plants. In response to salinity and gibberellic acid (GA₄), catalase (CAT), superoxide dismutase, and reduced glutathione were significantly regulated in LK11 as compared to peroxidase (POD) and polyphenol oxidase (PPO). Salinity stress to tomato plants caused significant cessation in growth and biomass, which was accompanied by threefold increase in lipid peroxidation and decrease in glutathione, CAT, POD, and PPO activities. In contrast, sole and combined treatment of LK11 and GA₄ rescued plant growth and biomass production whilst exhibited lower lipid peroxidation and higher glutathione content under salinity stress. The activities of CAT, POD, and PPO were either lower or nonsignificant as compared to control. In conclusion, inoculation of bacterial endophytes offers a relative stress counteracting potentials as evidenced by the known plant growth regulators.     

A potential antioxidant resource: Endophytic fungi from medicinal plants

Medicinal plants and their endophytes are important resources for discovery of natural products. Several previous studies have found a positive correlation between total antioxidant capacity (TAC) and total phenolic content (TPC) of many medicinal plant extracts. However, no information is available on whether such a relationship also exists in their endophytic fungal metabolites. We investigated the relationship between TAC and TPC for 292 morphologically distinct endophytic fungi isolated from 29 traditional Chinese medicinal plants. The antioxidant capacities of the endophytic fungal cultures were significantly correlated with their total phenolic contents, suggesting that phenolics were also the major antioxidant constituents of the endophytes. Some of the endophytes were found to produce metabolites possessing strong antioxidant activities. Several bioactive constituents from the fungal cultures and host plant extracts were identified. This investigation reveals that the metabolites produced by a wide diversity of endophytic fungi in culture can be a potential source of novel natural antioxidants.     

Expression of defence-related peroxidases Prx7 and Prx8 during abiotic stresses in barley roots

The expression of defence-related peroxidases Prx7 and Prx8 in barley roots grown under selected abiotic stress conditions (toxic metals: Cd, Al, Co, Cu, Hg; drought, salinity, extreme temperatures: heat, cold) and compounds activating (2,4-D) or inhibiting (SHAM) POD activity as well as H₂O₂ and H₂O₂ scavenger (DTT) was characterized. Strong Cd concentration dependent expression of Prx8 peroxidase gene was observed, which correlated with root growth inhibition induced by Cd- and some other stress factors (heavy metals, heat and salinity). Application of H₂O₂ did not cause changes in expression of Prx8, but H₂O₂ scavenger (DTT) as well as the inhibitor (SHAM) and the activator (2,4-D) of PODs induced increase in Prx8 expression. Our results demonstrate that root growth inhibition during any disturbance of active oxygen species (AOS) in root tissue is correlated with up-regulation of Prx8 gene expression in barley roots.     

Endophytic fungi as biocontrol agents: elucidating mechanisms in disease suppression

ABSTRACT

Background

Fungal endophytes occur ubiquitously in plants and are being increasingly studied for their ability to support plant health and protect the host from diseases. Using endophytes in disease control provides potential advantages compared to other biocontrol agents since they colonise the plant internally and thereby stay protected from environmental stresses and fluctuations. A thorough understanding of their mechanisms is required in their mutualistic association with plants; both to optimise their efficacy and for registration as plant protection products.     

Hydrogen sulfide regulates abiotic stress tolerance and biotic stress resistance in Arabidopsis

Hydrogen sulfide (H2S) is an important gaseous molecule in various plant developmental processes and plant stress responses. In this study, the transgenic Arabidopsis thaliana plants with modulated exp...     

Biosynthesis and beneficial effects of microbial gibberellins on crops for sustainable agriculture

Soil microbes promote plant growth through several mechanisms such as secretion of chemical compounds including plant growth hormones. Among the phytohormones, auxins, ethylene, cytokinins, abscisic acid and gibberellins are the best understood compounds. Gibberellins were first isolated in 1935 from the fungus Gibberella fujikuroi and are synthesized by several soil microbes. The effect of gibberellins on plant growth and development has been studied, as has the biosynthesis pathways, enzymes, genes and their regulation. This review revisits the history of gibberellin research highlighting microbial gibberellins and their effects on plant health with an emphasis on the early discoveries and current advances that can find vital applications in agricultural practices.     

茅苍术内生真菌的分离鉴定及在组培苗中的回接

从茅苍术的叶、茎和根中分离鉴定内生真菌,并观测内生菌回接对茅苍术组培苗生长的影响。共获得茅苍术内生菌16株,其中叶片中14株,根茎中各获得一株。分别为交链孢霉、镰刀霉、小克银汉霉、青霉、茎点霉、小菌核菌、孔球孢霉和不产孢类。经内生菌和茅苍术快繁苗实验初筛,得到两株对植物无害的内生菌:小菌核菌和孔球孢霉,将它们回接到茅苍术组培苗中,可以从苗叶片中染色观察到菌丝。其中小菌核菌能提高茅苍术炼苗的存活率,接入内生菌的茅苍术叶片超氧化物歧化酶和过氧化物酶活性均高于未接菌的对照,脂肪酸不饱和指数基本不变,说明分离自茅苍术的内生菌回接后可以与宿主建立共生关系。     

内生真菌与宿主植物协同调控砷胁迫作用机制研究进展

丛枝菌根真菌(arbuscular mycorrhizal fungi,AMF)和深色有隔内生真菌(dark septate endophytes, DSE)是植物根系中最主要的两大类内生真菌,均可与植物根系形成菌根共生体,在促进植物生长,提高重金属等胁迫抗性方面发挥着重要作用。砷(arsenic, As)及砷化合物具有较强的毒性,可在植物中富集,造成生物链毒害。本团队一直致力于内生真菌与药用植物生长、活性物质合成,砷吸收、积累关系的研究,并取得了一定的进展。结合团队现有研究和前人研究成果,本文分析归纳了砷胁迫条件下,AMF定殖对宿主植物生长和砷吸收、积累的影响;详细阐述了砷胁迫条件下,宿主植物生理活动、抗氧化系统、激素水平、转录水平响应AMF调控的变化。其后,从宿主植物细胞内、外两个方面总结内生真菌与宿主植物协同调控砷胁迫的作用机制,归纳为“生长稀释效应”“菌丝隔离”“螯合过滤”“菌根固定化(mycorrhizal immobilization)”“转运体抑制效应”“生物转化作用”和“保宿主、降氧化”等7项作用机制,并绘制了不同机制之间的作用关系图。DSE-宿主植物调控砷胁迫的研究相...     

内生菌莫拉维假单胞菌GF-55促进玉米生长和提高抗倒伏功能分析

【背景】内生菌对作物生长发育和抗逆性有重要作用,本团队分离筛选了一株显著促进玉米生长的莫拉维假单胞菌(Pseudomonas moraviensis)GF-55。【目的】揭示莫拉维假单胞菌GF-55的促生抗倒伏能力。【方法】开展了盆栽及温室种植试验,并测定了玉米生长发育和抗倒伏相关指标。【结果】通过分析表明,GF-55菌处理与对照相比,玉米株高、苗干重和苗鲜重分别增加43.47%、26.67%和82.44%,根干重、鲜重、长、体积、表面积和平均直径分别增加231.25%、96.42%、141.68%、46.51%、37.07%和52.38%。菌株GF-55分泌生长激素吲哚乙酸(indole-3-acetic acid,IAA)、嗜铁素相对含量和解磷量分别为30.88μg/mL、50.20%和58.43 mg/L;温室试验发现施菌处理可显著提高玉米吐丝期后茎秆的抗倒伏效果,玉米茎秆穿刺、弯曲和压碎强度较对照分别增加15.78%、55.83%和33.71%。施菌处理的秸秆半纤维素、纤维素和木质素含量较对照分别增加10.56%、2.91%和48.01%。【结论】莫拉维假单胞菌GF-55具有促...     

药用植物内生真菌研究现状及其应用前景

随着对药用植物内生真菌研究的深入,从药用植物内生真菌中寻找新的生物活性成分已成为研究热点。内生真菌对药用植物的生长及活性成分的形成都有影响,内生真菌活性成分已成为发现新颖结构化合物及新药物的潜在资源。简要综述了近年来在内生真菌的分离鉴定、发酵、次生代谢产物、与宿主的关系等方面的研究进展。