壳寡糖诱导的烟草SKP1基因表达

壳寡糖是一种高效的植物抗性诱导剂,应用mRNA差异显示技术从经过壳寡糖诱导的枯斑三生烟草叶片中分离到了编号为5、31、37和46的4个基因片段.4个基因片段与本塞姆氏烟草(Nicotiana benthamiana)SKP1基因的mRNA同源性都达到82%,据此推断这4个片段是感病烟草品种枯斑三生烟草的SKP1基因.质粒双酶切及反向Northern分析结果表明,该基因表达在壳寡糖诱导下增强.由于SKP1基因与植物的抗病毒病相关,从而在mRNA水平上验证了壳寡糖的诱导抗性效应.     

一氧化氮在寡糖素诱导的小麦对条锈菌系统获得抗性中的时序性

研究了寡糖素在诱导感病小麦品种辉县红系统抗条锈性中的作用,同时利用ESR测定了系统获得抗性（SAR）中一氧化氮(NO)的时间进程,结果表明寡糖素可以诱导辉县红对条锈菌毒性小种CY29-1的系统抗性,此系统抗性与内源NO信号启动的时间及强度有关.     

壳寡糖对烟草花叶病毒的体外钝化作用

壳寡糖是一种由脱乙酰基几丁质经酶降解后制备的氨基葡萄糖,它具有多方面的生物活性,在调节植物的生理机能、调控植物形态发生、诱导植物抗病性、抗逆性以及抑制真菌、细菌的生长发育等方面的作用多有报道,但关于壳寡糖对植物病毒的抑制作用未见报道.     

壳寡糖诱导植物抗性相关基因mRNA差别显示分析

壳寡糖是一种天然的信号分子,可以诱导植物产生各种防御反应。该文利用mRNA显示技术。研究壳寡糖引起的植物抗性相关基因的变化。以50mg/l壳寡糖喷洒的烟草叶片为材料,分别提取处理8h、7d和对照的叶片总RNA,利用一个锚定引物和三个随机引物组合,通过mRNA差别显示技术共获得壳寡糖处理后发生变化的8h差别条带22条,7d后的差别条带为74条。将壳寡糖处理8h得到的17条差别条带克隆到载体上后,进行反向Northern鉴定,有6条可能为真实条带。测序结果表明：其中一条差别片段与烟草热激蛋白90基因具有97％的核苷酸同源性。说明50mg/l壳寡糖处理的烟草叶片在mRNA水平上发生了明显的变化,烟草的热激蛋白90基因可能参与到壳寡糖诱导的抗性信号传导通路中。     

混合真菌发酵制备支化β-1,3-葡寡糖

真菌来源的β-1,3-葡聚糖被证实具有很好的抗肿瘤、免疫调节功能,但其过大的分子量和水不溶性影响其功能和应用,研究表明低分子量结构的葡寡糖具有更好的水溶性和生物活性。因此,本研究将能产这种结构多糖的真菌与能产内切β-1,3-葡聚糖酶的哈茨木霉混合发酵,从而得到低分子量的葡寡糖,并保留支链结构。本研究建立了齐整小核菌-哈茨木霉与裂褶菌-哈茨木霉混合发酵体系,制得了2种支化β-1,3-葡寡糖,分别为小核寡糖和裂褶寡糖。通过发酵条件优化,小核寡糖摇瓶产量最高为4.53 g/L,在7 L发酵罐中的产量最高为9.94 g/L,其中小核寡糖聚合度(DP)为5～12,裂褶寡糖DP为5～15。抗氧化实验表明,小核寡糖和裂褶寡糖都有较好的活性,且裂褶寡糖优于小核寡糖。本研究成功制得2种支化β-1,3-葡寡糖,并证明具有良好的水溶性和抗氧化活性。     

SPINDLY在壳寡糖诱导拟南芥抗丁香假单胞菌中的功能

为了探讨拟南芥O-岩藻糖基转移酶(SPINDLY)在病原体相关分子模式诱导抗性中的作用,该研究以SPINDLY缺失拟南芥突变体spy-3为实验材料,从叶片表型、病情指数、病菌定殖量以及丁香假单胞菌(Pst DC3000)关键基因的表达水平等指标,系统考察了SPINDLY在壳寡糖诱导拟南芥抗Pst DC3000中的功能。结果显示:(1)spy-3突变体比野生型更易被Pst DC3000侵染。(2)与病菌侵染组相比,壳寡糖预处理明显缓解植株叶片黄化现象,显著降低Pst DC3000的定殖量。(3)壳寡糖预处理的spy-3植株中水杨酸和茉莉酸途径相关基因的表达量及水杨酸和茉莉酸含量均较病菌侵染组明显升高。(4)壳寡糖在spy-3中的诱抗效果与野生型相比无明显差别。研究表明,SPINDLY在植物先天免疫过程发挥重要作用,但并不影响壳寡糖的诱导抗性。     

壳寡糖诱导植物防御反应中一氧化氮信号的研究

壳寡糖可以增强植物对病虫害的防御能力,为了深入研究壳寡糖的作用机理,首次运用荧光酶标仪及一氧化氮(Nitric oxide,NO)荧光探针Diaminofluorescein diacetate (DAF-2DA)对壳寡糖诱导的NO信号进行研究。研究发现,不同浓度的壳寡糖均可诱导烟草悬浮细胞产生NO;NO的清除剂Carboxy-PTIO potassium salt(cPTIO)和一氧化氮合酶(Nitric oxide synthase,NOS)抑制剂N^ω-nitro-L-arginine methyl Ester(L-NAME)可以明显抑制NO的产生;硝酸还原酶(Nitrate reductase, NR)的抑制剂叠氮化钠和钨酸钠对NO的产生无影响;Ca²⁺流相关抑制剂氯化镧和钌红均可抑制NO的产生。NO和Ca²⁺流的相关抑制剂可明显抑制壳寡糖诱导的抗性相关基因的表达。结果显示:壳寡糖主要通过NOS酶催化合成NO,且NO参与调节壳寡糖诱导的抗性相关基因的表达,在此过程中,Ca²⁺可以调节NO的合成。     

牛蒡寡糖诱导黄瓜抗炭疽病的研究

本研究证明了牛蒡寡糖能显著诱导黄瓜对炭疽病的抗性。黄瓜幼苗经0.05%的牛蒡寡糖处理后,以病斑数计算的对炭疽病诱抗效果为50.01%,以病斑面积计算的诱抗效果为56.83%。而用牛蒡寡糖诱导后,四种与植物抗性有关的酶的活性随诱导时间的延长呈现出不同的动态变化。β-1,3-葡聚糖酶在诱导后第4天的活性最高,超氧化物岐化酶(SOD)在诱导后第3天活性最高,多酚氧化酶(PPO)的活性从诱导后第4天开始持续升高,而过氧化氢酶(CAT)的活性在诱导后则有所降低,与同期对照相比最大降低幅度为29%。     

褐藻胶寡糖对毒死蜱胁迫下小麦幼苗生理生化指标的影响

褐藻胶寡糖对植物的生长发育具有调控作用。为了探讨褐藻胶寡糖对植物抗逆性的作用,以青丰Ⅰ号小麦种子为试验材料,探究了不同浓度褐藻胶寡糖(0、0.05%、0.1%、0.2%、0.4%)对毒死蜱胁迫下小麦生理特性的缓解作用。结果表明:毒死蜱显著降低小麦幼苗中叶绿素a、叶绿素b及总叶绿素含量(P0.05),使脯氨酸、可溶性蛋白及可溶性糖含量显著升高(P0.05),生物量降低,抑制地上部分生物量积累,根冠比增加;褐藻胶寡糖对这些生理生化指标的变化起到显著的缓解作用(P0.05);浓度为0.4%的褐藻胶寡糖缓解作用最为显著(P0.01)。因此,褐藻胶寡糖使毒死蜱对小麦幼苗的伤害有明显缓解作用,增强植物对毒死蜱胁迫的抗性。     

微生物诱导的植物系统抗性

综述了由植物病原菌和非病原性的根际促生菌诱导产生的两种植物系统抗性:系统获得性抗性(SAR)和系统诱导抗性(ISR),比较了两类系统抗性的诱导、信号分子和机理的异同点,阐述了信号分子水杨酸在系统获得性抗性诱导过程中的作用及茉莉酸和乙烯在系统诱导抗性产生过程中的作用。     

Evaluation of antagonistic activities of Bacillus subtilis and Bacillus licheniformis against wood-staining fungi: In vitro and in vivo experiments

The antifungal activity of bacterial strains Bacillus subtilis EF 617317 and B. licheniformis EF 617325 was demonstrated against sapstaining fungal cultures Ophiostoma flexuosum, O. tetropii, O. polonicum, and O. ips in both in vitro and in vivo conditions. The crude active supernatant fractions of 7 days old B. subtilis and B. licheniformis cultures inhibited the growth of sapstaining fungi in laboratory experiments. Thermostability and pH stability of crude supernatants were determined by series of experiments. FT-IR analysis was performed to confirm the surface structural groups of lipoproteins present in the crude active supernatant. Partial purification of lipopeptides present in the crude supernatant was done by using Cellulose anion exchange chromatography and followed by Sephadex gel filtration chromatography. Partially purified compounds significantly inhibited the sapstaining fungal growth by in vitro analysis. The lipopeptides responsible for antifungal activity were identified by electrospray ionization mass spectrometry after partial purification by ion exchange and gel filtration chromatography. Four major ion peaks were identified as m/z 1023, 1038, 1060, and 1081 in B. licheniformis and 3 major ion peaks were identified as m/z 1036, 1058, and 1090 in B. subtilis. In conclusion, the partially purified lipopeptides may belong to surfactin and iturin family. In vivo analysis for antifungal activity of lipopeptides on wood was conducted in laboratory. In addition, the potential of extracts for fungal inhibition on surface and internal part of wood samples were analyzed by scanning electron microscopy.     

Functional expression in Aspergillus oryzae of p15, a protein with potent neurite-inducing activity in PC12 cells

We previously reported that a fungal protein, p15, induces neurite outgrowth and differentiation of rat pheochromocytoma PC12 cells through the activation of the Ca2+ signaling pathway. We report here the secretory production of p15 in Aspergillus oryzae. Analysis of culture supernatant of A. oryzae transformed with the gene encoding the p15 precursor tagged with a hemagglutinin (HA) epitope demonstrated that the transformant secreted a protein with an apparent molecular mass of 17.5 kDa, which is a little larger than the expected size of mature p15-HA. By heat denaturation and ion exchange chromatography, p15-HA was easily purified from the culture supernatant with sufficient abundance. Although purified p15-HA was less active than the native p15 obtained from the culture broth of a producing fungal strain, it had neurite-inducing activity in PC12 cells in a dose-dependent manner, providing a system to study the action mechanism of p15.     

Molecular cloning, characterization, and expression of a redox-responsive cutinase from Monilinia fructicola (Wint.) Honey

cDNA clones encoding a cutinase expressed in cutin-induced cultures of the plant pathogen Monilinia fructicola were isolated using a protein-based strategy. The largest cDNA (Mfcut1) was found to contain an open reading frame of 603 bp that predicted a 20.2-kDa protein of 201 amino acids with a 20-amino-acid secretory signal peptide and a pI of 8.4. The predicted protein contained cutinase/lipase consensus sequences with active site serines and potential protein kinase phosphorylation sites. Comparison of the deduced amino sequence from Mfcut1 with other fungal cutinase sequences revealed new features, which include conserved cysteines, C-terminal aromatic residues, and a novel histidine substitution in the D-H active site motif. The presence in the growth medium of antioxidants, such as caffeic acid, suppressed mRNA accumulation and enzyme activity of a cutinase from M. fructicola. MFCUT1 was expressed at high levels as a His-tagged fusion protein in Pichia pastoris and purified to apparent homogeneity in a single step by Ni(2+)-nitrilotriacetic acid affinity chromatography. Analysis of variant MFCUT1 mutants in which the novel serine and histidine residues were replaced by site-directed mutagenesis indicated that these residues had an important effect on enzyme activity.     

Four glycosidases secreted by Collectotrichum lindemuthianum

The fungal plant pathogen, Collectotrichum lindemuthianum, was grown in culture with either galactose, arabinose or pectin as the carbon source resulting in the selective secretion of α-galactosidase, α-arabinofuranosidase and exopolygalacturonase, respectively. Each enzyme has been purified by ion exchange and gel permeation chromatography. In addition, a β-glucosidase was purified from the culture filtrate or arabinose grown fungus. The purified α-galactosidase and α-arabinosidase preparations were found to be essentially free of other carbohydrases while the β-glucosidase and exopolygalacturonase preparations contain contaminating activities.     

Penicillium solitum produces a polygalacturonase isozyme in decayed Anjou pear fruit capable of macerating host tissue in vitro

A polygalacturonase (PG) isozyme was isolated from Penicillium solitum-decayed Anjou pear fruit and purified to homogeneity with a multistep process. Both gel filtration and cation exchange chromatography revealed a single PG activity peak, and analysis of the purified protein showed a single band with a molecular mass of 43 kDa, which is of fungal origin. The purified enzyme was active from pH 3.5-6, with an optimum at pH 4.5. PG activity was detectable 0-70 C with 50 C maximum. The purified isozyme was inhibited by the divalent cations Ca(2+), Mg(2+), Mn(2+) and Fe(2+) and analysis of enzymatic hydrolysis products revealed polygalacturonic acid monomers and oligomers. The purified enzyme has an isoelectric point of 5.3 and is not associated with a glycosylated protein. The PG isozyme macerated fruit tissue plugs in vitro and produced ~1.2-fold more soluble polyuronides from pear than from apple tissue, which further substantiates the role of PG in postharvest decay. Data from this study show for the first time that the purified PG produced in decayed Anjou pear by P. solitum, a weakly virulent fungus, is different from that PG produced by the same fungus in decayed apple.     

Purification and characterisation of a novel laccase from the ascomycete Melanocarpus albomyces

A novel laccase from the ascomycete Melanocarpus albomyces was purified and characterised. The enzyme was purified using anion exchange chromatography, hydrophobic interaction chromatography and gel filtration, and the purified laccase was biochemically characterised. It had activity towards typical substrates of laccases including 2,2'-azinobis-(3-ethylbenzthiazoline-6-sulphonate), dimethoxyphenol, guaiacol, and syringaldazine. The laccase showed good thermostability and it had a pH optimum at neutral pH, both unusual properties for most known fungal laccases. The activity of the laccase from M. albomyces was highest at 60-70 degrees C. With guaiacol and syringaldazine the pH optima were rather broad: 5-7.5 and 6-7, respectively. It retained 50% of its activity after 5 h incubation at 60 degrees C. The molecular weight of the laccase was about 80 kDa and the isoelectric point 4.0. The ultraviolet-visible absorption and electron paramagnetic resonance spectra of the purified laccase indicated that the typical three types of copper were present.     

Purification of a multipotential colony-stimulating factor from pokeweed mitogen-stimulated mouse spleen cell conditioned medium

A factor able to stimulate the proliferation and differentiation of multipotential stem cells and progenitor cells of the granulocyte-macrophage, eosinophil, and erythroid lineages as well as being able to maintain factor-dependent cell lines in culture has been purified from pokeweed mitogen-stimulated mouse spleen cell-conditioned medium. The factor was purified over 2 million-fold by sequential fractionation using salting out chromatography, chromatography on phenyl-Sepharose, gel filtration on Sephadex G-75, ion exchange chromatography on DEAE-Sepharose, reverse-phase high performance liquid chromatography on a phenyl-silica column, and gel permeation high performance liquid chromatography. All of the biological activities ascribed to the multipotential colony-stimulating factor co-fractionated through all steps, and the other known mouse-active hemopoietic regulator in pokeweed mitogen-stimulated mouse spleen cell-conditioned medium, granulocyte-macrophage colony-stimulating factor, was separated at the ion exchange step. Two protein species having Mr = 24,000 and 19,000 were visualized by silver-staining of sodium dodecyl sulfate-polyacrylamide gels of the purified factor. Both species migrated coincidently with the biological activities. The factor was active at a half-maximal concentration of 1 X 10(-13) M when assayed on a factor-dependent cell line.     

Purification and characterization of a glutathione S-transferase from the fungus Cunninghamella elegans

Cunninghamella elegans grown on Sabouraud dextrose broth had glutathione S-transferase (GST) activity. The enzyme was purified 172-fold from the cytosolic fraction (120000 x g) of the extract from a culture of C. elegans, using Q-Sepharose ion exchange chromatography and glutathione affinity chromatography. The GST showed activity against 1-chloro-2,4-dinitrobenzene, 1,2-dichloro-4-nitrobenzene, 4-nitrobenzyl chloride, and ethacrynic acid. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis gel filtration chromatography revealed that the native enzyme was homodimeric with a subunit of M(r) 27000. Comparison by Western blot analysis implied that this fungal GST had no relationship with mammalian alpha-, mu-, and pi-class GSTs, although it showed a small degree of cross-reactivity with a theta-class GST. The N-terminal amino acid sequence of the purified enzyme showed no significant homology with other known GSTs.