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.     

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.     

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。     

野生抚育山参内生真菌分离鉴定

采用组织块法对野生抚育山参(Panax ginseng)根中内生真菌进行分离,共分离出16株内生真菌,根据形态鉴定出10株,分别隶属于头孢属(Cephalosporium)、青霉属(Penicillium)、柱孢属(Cylindrocarpon)、轮枝孢属(Verticillium)、单端孢属(Trichothecium)。以金黄色葡萄球菌(Staphylococcus aureus)、大肠杆菌(Escherichia coli)、白色念珠菌(Candida albicans)为指示菌对内生真菌进行抑菌活性筛选,共筛选出2株内生菌,这2株内生菌对金黄色葡萄球菌有较强的抑制作用。     

Screening for Endophytic Fungi with Antitumour and Antifungal Activities from Chinese Medicinal Plants

Summary One hundred and thirty endophytic fungi isolated from 12 Chinese traditional medicinal plants collected at Yuanmou county and Dawei Mountain, Yunnan province, southwest China, were tested for antitumour and antifungal activities by MTT assay on human gastric tumour cell line BGC-823 and the growth inhibition test against 7 phytopathogenic fungi. The results showed that fermentation broths from 9.2% of the isolates exhibited antitumour activity and 30% exhibited antifungal activity, moreover, some of them exhibited broad-spectrum antifungal activity. The active isolates were identified to 32 taxa. The results indicate that the endophytic fungi of Chinese traditional medicinal plants are promising sources of novel bioactive compounds.     

红树植物内生真菌的分离鉴定及抗菌活性菌株的筛选

本文对厦门集美红树植物无瓣海桑(Sonneratia apetala),海马齿(Sesuvium portulacastrum)和秋茄(Kan-delia candel)的多个部位进行内生真菌的分离和形态鉴定,并采用菌饼法对分离到的内生真菌进行抗菌活性筛选。结果显示,从3种红树植物的根、茎、叶中分离得到25株内生真菌,分别隶属8个类群,以链格孢属和曲霉属为主,分别占菌株总数的28.0%和24.0%;有19株菌株对至少一种指示菌有抑制作用,占菌株总数的76.0%。研究结果表明,红树植物来源的内生真菌数量多,种属丰富,同时具有良好的抗菌活性,是研究抗菌活性化合物的重要资源。     

NAC转录因子在植物抗病和抗非生物胁迫反应中的作用

NAC转录因子是植物特有的一类转录因子,其共同特点是在N端含有一段高度保守、由约150个氨基酸组成的NAC结构域,而C端为高度变异的转录调控区。研究表明,NAC转录因子不仅参与植物生长发育的调控,而且在植物抗逆反应中具有重要的调控作用。文章着重介绍NAC转录因子在植物抗逆反应中的作用及其调控机制,并简要讨论NAC转录因子生物学功能的研究方向。     

蛇足石杉产石杉碱甲内生真菌的分离鉴定

从9月份采集的野生药用植物蛇足石杉(Huperzia serrata)的茎、叶中分离纯化得到15株内生真菌,将上述内生真菌进行液体培养后,通过薄层层析法(TLC)和高效液相法(HPLC)对其代谢产物进行检测,结果表明菌株WX13产石杉碱甲(Huperzine A,HupA)。运用形态和培养特性观察,初步确定菌株WX13属于镰刀菌属(Fu-sarium sp.)。     

云南12种药用植物内生真菌分离及抗肿瘤活性菌株筛选

从马尾树、断肠草和白花蛇舌草等十二种云南药用植物中共分离到内生真菌263株,以卤虫模型对其中130株进行了抗肿瘤活性筛选,结果表明,有56.9%的菌株LD50≥4,39.2%的菌株LD50≥8,25.4%的菌株LD50≥16。以人胃癌细胞株BGC-823对LD50≥16的高活性菌株进行MTT法复筛,结果表明,有12株菌显示了细胞毒活性,抑制率从39.24%到100%不等。进一步研究表明,菌株D126和MT13对人白血病细胞株K562显示了较强的细胞毒活性,IC50分别为1∶438和1∶919。在12种植物中,小桐子的抗肿瘤活性菌株比率最高,为37.5%,其次为曼陀罗,为25.0%,而乌头、木瓜红、大花八角和重楼中未分离到抗肿瘤活性菌株。经鉴定,抗肿瘤活性菌株分属于12个分类单元     

Gibberellin physiology of safflower: endogenous gibberellins and response to gibberellic acid

Endogenous gibberellins (GAs) were extracted from safflower (Carthamus tinctorius L.) stems and detected by capillary gas chromatography-mass spectrometry from which GA₁, GA₃, GA₁₉,, GA₂₀, GA₂₉, and probably, GA₄₄ were detected. The detection of these GAs suggests that the early 13-OH biosynthetic pathway is prevalent in safflower shoots. Deuterated GAs were used as internal standards and GA concentrations were determined in stems harvested at weekly intervals. GA₁ and GA₁₉ levels per stem increased but concentrations per gram dry weight decreased over time. GA₂₀ was only detected in young stem tissue.Gibberellic acid (GA₃) was also applied in field trials and both GA₃ and the GA biosynthetic inhibitor, paclobutrazol, were applied in growth chamber tests. GA₃ increased epidermal cell size, internode length, and increased internode cell number causing stem elongation. Conversely, paclobutrazol reduced stem height, internode and cell size, cell number and overall shoot weight. In field tests, GA₃ increased total stem weight, but decreased leaf weight, flower bud number and seed yield. Thus, GA₃ promoted vegetative growth at the expense of reproductive commitment. These studies collectively indicate a promotory role of GAs in the control of shoot growth in safflower, and are generally consistent with gibberellin studies of related crop plants. Author for correspondence     

Endophytic fungi from a pharmaceutical plant, Camptotheca acuminata: isolation, identification and bioactivity

About 174 endophytic fungi were isolated from the pharmaceutical plant, Camptotheca acuminata. Of the 18 taxa obtained, non-sporulating fungi (48.9%), Alternaria (12.6%), Phomopsis (6.9%), Sporidesmium (6.3%), Paecilomyces (4.6%) and Fusarium (4.6%) were dominant. ITS rDNA assay indicated that most of the non-sporulating fungi belonged to the Pyrenomycetes and Loculoascomycetes ascomycetes or their anamorph Coelomycetes. The results of the bioactivity test showed that 27.6% of the endophytic fungi displayed inhibition against more than one indicator microorganism. 4.0% and 2.3% of the endophytic fungi showed cytotoxicity and protease inhibition, respectively. The endophytic fungi with bioactivities were distributed in more than 12 taxa including non-sporulating fungi, which are reliable sources for bioactive agents.