Immunohistochemical investigation of cotton carpel tissue exposed to xylanolytic hydrolases of Aspergillus flavus

Cotton carpel tissue (35–45 days post-anthesis) that had been treated with a mixture of xylanolytic hydrolases derived from Aspergillus flavus was subjected to immunocytochemical analysis. Microscopic examination of treated tissues revealed severe degradation of the secondary wall structure. Control tissue cells revealed the presence of high concentrations of xylans/arabinoxylans throughout the cell wall, as well as significant concentrations of arabinogalactan proteins in secondary wall structure. Carpel cells treated with a mixture of A. flavus-produced xylanolytic hydrolases showed a much reduced presence of labeling by xylan-specific antibodies on the inner wall surface, suggesting a severe loss of these plant polysaccharides in the secondary wall structure. Carpel exposure to a purified 14 kD endoxylanase from A. flavus also resulted in a severe reduction of xylans from secondary wall structure, although penetration of the tissue was not as dramatic. Arabinogalactan proteins were not as severely affected by the xylanolytic hydrolases. Comparison of control tissue with hydrolase-treated tissue stained with toluidine blue revealed an apparent reduction in wall thickness, supporting the conclusion of secondary wall structure degradation. Interestingly, the pectins could only be detected in the samples treated with xylanolytic enzymes, indicating that the pectins were being masked by xylans. These results are consistent with the conclusion that the xylanolytic hydrolase complex of A. flavus is a critical factor for host cell wall maceration and may represent another important fungal virulence factor, in addition to pectolytic hydrolase activities.     

Regulation of flower development in Dendrobium crumenatum by changes in carbohydrate contents,water status and cell wall metabolism

The involvement of carbohydrates, water potential, cell wall components and cell wall-based enzymes in regulating flower development in Dendrobium crumenatum was investigated. Plants were subjected to cold treatment to release floral buds from dormancy, and the various parameters were investigated from young floral bud stage till flower senescence. Development of floral buds was accompanied by progressive decrease in concentrations of fructans and starch. Upon full flower opening, concentration of soluble sugars was maximum, accompanied by a more negative water potential. High pectin methylesterase activity was observed during early bud development and decreased thereafter. Significant increase in activities of β-galactosidase, β-mannosidase and β-xylosidase was also observed during floral bud development. The cell walls of sepals and petals were modified extensively during floral bud and flower development, as observed by changes in the amounts of celluloses, hemicelluloses and total pectin. Pectin solubilisation was also observed to commence during early floral bud development. These results indicated that carbohydrate hydrolysis, osmotic changes and cell wall dissolution that began early in young floral buds, all regulated flower development in this sympodial orchid. Possible applications of the findings in the horticultural industry are discussed.     

Comparative Analysis of Glycoside Hydrolases Activities from Phylogenetically Diverse Marine Bacteria of the Genus Arenibacter

A total of 16 marine strains belonging to the genus Arenibacter, recovered from diverse microbial communities associated with various marine habitats and collected from different locations, were evaluated in degradation of natural polysaccharides and chromogenic glycosides. Most strains were affiliated with five recognized species, and some presented three new species within the genus Arenibacter. No strains contained enzymes depolymerizing polysaccharides, but synthesized a wide spectrum of glycosidases. Highly active β-N-acetylglucosaminidases and α-N-acetylgalactosaminidases were the main glycosidases for all Arenibacter. The genes, encoding two new members of glycoside hydrolyses (GH) families, 20 and 109, were isolated and characterized from the genomes of Arenibacter latericius. Molecular genetic analysis using glycosidase-specific primers shows the absence of GH27 and GH36 genes. A sequence comparison with functionally-characterized GH20 and GH109 enzymes shows that both sequences are closest to the enzymes of chitinolytic bacteria Vibrio furnissii and Cellulomonas fimi of marine and terrestrial origin, as well as human pathogen Elisabethkingia meningoseptica and simbionts Akkermansia muciniphila, gut and non-gut Bacteroides, respectively. These results revealed that the genus Arenibacter is a highly taxonomic diverse group of microorganisms, which can participate in degradation of natural polymers in marine environments depending on their niche and habitat adaptations. They are new prospective candidates for biotechnological applications due to their production of unique glycosidases.     

The influence of exposure to light on the phenolic content of ‘Fuji’ apple

In this study, the influence of changes in fruit lighting on individual and total phenols in ‘Fuji’ apple, as well as color development was studied. Content levels of eight quercetin glycosides, five anthocyanins, two catechins and a hydroxycinnamic acid in the skin of apples were analyzed, using high-performance liquid chromatography, tandem mass spectrometry (HPLC-MS). Total phenol, chlorophyll and carotenoid contents were determined by spectrometry. The purpose of this study was to compare content levels of those compounds in apple skin of fruit grown in different parts of the tree canopy, under and outside of the hail net. Lighting of fruit was measured during the last month before harvest. The lowest values were measured in the inner fruit and higher ones in the outer parts of the canopy, while the highest values were measured in fruit growing at the top of the tree. The hail net had no influence on the decrease of lighting in comparison to the control. Light conditions in the tree canopy influenced lower content levels of quercetin glycosides and most anthocyanins in the fruit skin in the inner part of the tree canopy, whereas fruit from the canopy top contained the highest levels of quercetin glycosides and cyanidin glycosides. Catechin, epicatechin and chlorogenic acid content levels in apple skin were independent of fruit position in the canopy or hail net usage, except for chlorogenic acid, where the content level was higher in cases when the orchard was covered with a hail net. Fruit from the top and outer parts of the canopy had a darker and redder coloration than inner fruit, while no influence of canopy position on chlorophyll and carotenoids was detected. Since quercetin glycosides and cyanidin glycosides are influential in red skin color development, better coloration of fruit from the outer and top canopy was observed. More intensive lighting stimulated a higher content level of flavonoids and, consequently, better coloration, which is an important factor in fruit quality.     

高氰和低氰木薯生氰葡萄糖苷酶Linamarase基因的组织表达差异分析

旨在降低或去除木薯的生氰糖苷,获得安全无毒木薯新品种。本研究以高氰和低氰5 个品种的木薯为材料,通过RT-PCR 方法,研究了生氰葡萄糖苷酶基因Linamarase 在木薯中的表达情况。木薯Linamarase 基因只在地上部分表达;5 个木薯品种,包括低氰和高氰品种,在块根中也均未检测到Linamarase 基因的表达。在地上部分中,顶芽的表达量要远远大于茎和成熟叶片的表达量,而且低氰和高氰品种在顶芽的表达量基本相同,但是低氰品种茎及成熟叶片中Linamarase 的表达量比高氰品种相对较高。木薯生氰糖苷酶Linamarase 在不同木薯品种不同组织的表达情况的不同,可以为筛选安全无毒木薯品种提供一个参考。     

Chemical constituents from Gmelina arborea bark and their antioxidant activity

Gmelina arborea Roxb. is a fast-growing species and is known to have been used in traditional Indian medicine. Chemical constituents from the bark have not been reported, although some chemical constituents from part of this plant (heartwood, leaf, and root) are known. In this study, the bark meal was successively extracted with acetone and methanol. Fractionation of the acetone extract with n-hexane, diethyl ether, and ethyl acetate and subsequent chromatographic separation of the fractions led to the isolation of four compounds. The diethyl ether-soluble fraction yielded tyrosol [2-(4-hydroxyphenyl)ethanol] (1); (+)-balanophonin (2), an 8-5′ neolignan, with opposite optical rotation to known (−)-balanophonin; and gmelinol (3), a known lignan. The ethyl acetate-soluble fraction afforded a new phenylethanoid glycoside to the best of our knowledge, which was identified as (−)-p-hydroxyphenylethyl[5′″-O-(3,4-dimethoxycinnamoyl)-β-d-apiofuranosyl(1′" → 6′)]-β-d-glucopyranoside (4). From the methanol extract, two known compounds, 2,6-dimethoxy-p-benzoquinone (5) and 3,4,5-trimethoxyphenol (6), were isolated and identified. The 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging assay of the identifi ed compounds indicated that 3,4,5-trimethoxyphenol (6) exhibited moderate activity. Part of this report was presented at the 57th and 58th Annual Meetings of the Japan Wood Research Society, Hiroshima and Tsukuba, August 2007 and March 2008, respectively     

A new naphthalene glycoside from the roots of Smilax bockii

From the roots of Smilax bockii a new compound, 7-hydroxymethyl-1, 4, 5-trihydroxynaphthalene-4-O-beta-D-xylopyranosyl(1-->6)-beta-D-glucopyranoside, was isolated. The structure of the new compound was elucidated on the basis of spectroscopic methods.     

黔产竹节参总黄酮苷的提取与测定方法研究

［目的］探讨黔产竹节参黄酮苷的提取与检测方法。［方法］以80%乙醇为溶剂,研究了黔竹节参黄酮苷的提取方法,并建立了竹节参黄酮苷的测定方法。［结果］黔产竹节参黄酮苷的提取率为0.981 8%,精制黄酮苷的含量为96.2%;采用分光光度法检测黔产竹节参黄酮苷浓度,对照样品回归方程y=-0.003 00＋0.011 01x,r=0.999 30,对照样品的加标回收率为100.36%。［结论］该方法操作简便快速准确,能满足黔产竹节参中总黄酮苷的提取和检测的要求。     

外源乙烯对不同成熟度网纹甜瓜果实细胞壁水解酶活性的影响

用浓度为10μL·L-1的外源乙烯处理不同成熟度网纹甜瓜(20℃,24 h),研究外源乙烯对果实硬度、ⅱ呼吸速率、乙烯释放量及细薄壁水解酶活性(多聚半乳糖醛酸酶、果胶甲酯酶和羧甲摹纤维素钠酶)、脂氧合酶和外渗电导率的影响.结果表明,无论果实是否达到完熟状态,与对照组相比,外源乙烯处理能够显著提高成熟和完熟网纹甜瓜果实呼吸速率和乙烯释放量以及细胞壁水解酶和脂氧合酶活性和外渗电导率,使它们的果实硬度迅速降低.但是不同成熟度的甜瓜果实对外源乙烯的敏感性存在差异,即与成熟果实相比,外源乙烯更显著地提高完熟果实的以上各个指标,从而使乙烯处理后的成熟果实硬度下降的速度更快.另外从对外源乙烯的相应时间来看,外源乙烯处理后完熟果实的以上各指标立即升高,而成熟果实在乙烯处理后1～3 d与成熟果实对照差异不明显,处理后6～12 d乙烯处理组和对照组差异逐渐加大.说明外源乙烯处理可以进一步提高成熟和完熟果实中细胞壁水解酶活性,进而促进细胞的降解,加快不同成熟度甜瓜果实后熟软化进程.     

A new triglucosylated naphthalene glycoside from Aloe vera L.

A new triglucosylated naphthalene derivative, named aloveroside A (1), together with two known anthraquinone dimers and two 6-phenyl-2-pyrone derivatives, was isolated from the Aloe vera ethanolic extracts. The structure of 1 was established as 1-(((4-(1-O-β-D-glucopyranosyl -(1→4)-β-D-xylopyranoside)-hydroxymethyl)-1-hydroxy-8-O-α-L-rhamnopyranoside)naphthalene-2-yl)-ethanone by means of spectroscopic evidences and chemical methods. All these compounds were tested for their BACE inhibitory activity but no significant activities were found.