Simple methods to remove microbes from leaf surfaces

Endophytes have been defined as microorganisms living inside plant tissues without causing negative effects on their hosts. Endophytic microbes have been extensively studied for their plant growth-promoting traits. However, analyses of endophytes require complete removal of epiphytic microorganisms. We found that the established tests to evaluate surface sterility, polymerase chain reaction, and leaf imprints, are unreliable. Therefore, we used scanning electron microscopy (SEM) as an additional assessment of epiphyte removal. We used a diverse suite of sterilization protocols to remove epiphytic microorganisms from the leaves of a gymnosperm and an angiosperm tree to test the influence of leaf morphology on the efficacy of these methods. Additionally, leaf tissue damage was also evaluated by SEM, as damaging the leaves might have an impact on endophytes and could lead to inaccurate assessment of endophytic communities. Our study indicates, that complete removal of the leaf cuticle by the sterilization technique assures loss of epiphytic microbes, and that leaves of different tree species may require different sterilization protocols. Furthermore, our study demonstrates the importance of choosing the appropriate sterilization protocol to prevent erroneous interpretation of host-endophyte interactions. Moreover, it shows the utility of SEM for evaluating the effectiveness of surface sterilization methods and their impact on leaf tissue integrity.     

Host-Species Variation and Environment Influence Endophyte Symbiosis and Mycotoxin Levels in Chinese Oxytropis Species

Oxytropis plants are widely distributed in the grasslands in northern China. Some Oxytropis species have been reported to contain the mycotoxin swainsonine, an alkaloid which causes poisoning in livestock, referred to as locoism. Previous studies showed that endophytic fungi (Alternaria oxytropis) symbiotically associate with these Oxytropis species to produce swainsonine. However, the influence of variation within the Oxytropis genus on the fixation or loss of symbiosis and toxicity is poorly understood, as is the influence of environmental factors. Here we used a collection of 17 common Oxytropis species sampled in northern China to assess genetic diversity using genotyping by sequencing which was compared with the levels of the endophyte and swainsonine. Results showed that nine Oxytropis species have detectable A. oxytropis colonisation, and seven Oxytropis species contain sufficient swainsonine to be considered poisonous, whereas the rest may be non-toxic. Species variation rather than the genetic lineage was associated with the fixation or loss of endophyte and swainsonine production, which appears to have resulted from genetic drift. Genotype × Environment (G × E) effects were also found to influence endophyte and swainsonine levels amongst species of the Oxytropis genus. Our study will provide a better understanding about the evolutionary basis of A. oxytropis symbiosis and swainsonine biosynthesis in locoweeds.     

金钱松内生真菌JJ18杀螺作用实验研究

目的:研究金钱松内生真菌JJ18的杀螺作用、活性部位及该菌株杀螺活性的传代稳定性,从而探索其应用的可能性。方法:按照WHO的杀螺剂浸泡试验法观察不同处理下JJ18发酵液杀螺效果。结果:JJ18菌株发酵液的活性成分集中在胞外液,当胞外液浓度10%时,72h杀螺率接近90%,且发酵外液成盐后有良好的耐热性,强光照下7 d内活性物质基本不改变,菌株传代稳定,杀螺活性成分集中在正丁醇萃取部位。结论:金钱松内生真菌JJ18代谢产物的杀螺活性,有开发应用的可能性。     

快速筛选金钱松内生真菌抗真菌活性的研究

目的：筛选金钱松内生真菌抗病源真菌的活性菌株。方法：首次对金钱松内生真菌进行了分离,以稻瘟霉PyricuLaria oryza P-2b为筛选模型,采用微量稀释法筛选金钱松内生真菌抗真菌活性,研究其抗病源真菌的能力。结果：金钱松内存在着大量且具有抗稻瘟霉P-2b活性的内生真菌,占内生真菌总数的44.8％。其中JJ314,JJ323可诱导稻瘟霉P-2b菌丝念珠状、膨大变形,JJ324可抑制孢子萌发,它们对红色毛癣菌Trichophyton rubrum、新型隐球菌Cryptococcus neoformans、白色念珠菌Candida albicans等病源真菌都具有强烈的活性。结论：金钱松内生真菌是潜在的抗真菌药物资源。     

几种蕨类植物内生真菌抑制病原菌的筛选

本文对从凤尾蕨(Pteris multifida Poir)、狗脊(Cibotium barometz)、半边旗(Pteris semipinnata)中分离得到的内生真菌及其发酵液进行了抑菌研究,结果表明蕨类植物内生真菌只对细菌病原菌有明显抑制作用。     

A new α-pyrone metabolite from a mangrove plant endophytic fungus,Fusarium sp.

A new α-pyrone derivative, compound 2, and a known one, cladobotrin V, were isolated from the culture broth of the mangrove endophyte Fusarium sp. IM-37. Their structures were determined spectroscopically and compared with previously reported spectral data. Compound 2 restored the growth inhibition caused by hyperactivated Ca²⁺-signaling in mutant yeast.     

The β-tubulin gene of Epichloë typhina from perennial ryegrass (Lolium perenne)

Summary Epichloë typhina is a biotrophic fungal pathogen which causes choke disease of pooid grasses. The anamorphic state, Acremonium typhinum, is placed in the section Albo-lanosa along with related, mutualistic, seeddisseminated endophytes. As an initial study of gene structure and evolution in Epichloë and related endophytes, the -tubulin gene, tub2, of the perennial ryegrass choke pathogen (EtPRG) was cloned and sequenced. The coding sequence and the predicted -tubulin amino acid sequence were highly homologous to the Neurospora crassa homologs, and to one of the two -tubulin genes of Emericella nidulans. However, two introns characteristic of the N. crassa and Em. nidulans genes were absent in the E. typhina gene. Furthermore, one of the remaining introns possessed the uncommon 5 splice junction, GC. In contrast to published observations concerning other Ascomycetes, a mutant of EtPRG, selected for resistance to methyl-2-benzimidazole carbamate (benomyl), possessed no alteration of its -tubulin coding sequence.     

药用植物内生真菌研究进展

综述药用植物内生真菌的生物多样性、内生真菌与宿主植物的关系及其内生真菌产生的活性代谢产物。分析了药用植物内生真菌研究所存在的问题及其研究的特殊性,为药用植物内生真菌研究提供了科学依据。     

内生菌药用新资源与道地药材的关系探讨

内生菌广泛地存在于植物组织内部。近20年来从内生菌中发现了很多结构新颖的活性次生产物,这些内生菌及相应产物对植物及相应化学组分含量有不同程度的影响。不同产地的同种药材中各种化学组分种类以及含量存在一定差异,一直以来认为这些差异源于气候、土壤、温度等外环境的影响,近期对于内生菌的研究表明,微生物也是影响药材质量的一个关键因素。内生菌自身产生或刺激宿主产生特定化学产物,或参与到特定物质的代谢途径中,从而影响药材的化学组分及各组分含量。本研究对内生菌作为一种药用新资源以及与植物药材质量的关系进行初步探讨。