Colonization and histopathology of susceptible and resistant carnation cultivars infected with Fusarium oxysporum f. sp. dianthi

Stems of the susceptible Early Sam and resistant Novada carnations were inoculated with a conidial suspension ofFusarium oxysporum f. sp.dianthi. Stem segments of either cultivar were sampled regularly and used for determination of fungal growth and for microscopical investigation.Early Sam showed typicalFusarium wilt symptoms and its stems were colonized intensively. The observed vascular browning appeared to be caused by discolouration of primary walls of infected vessels and surrounding cells. Vessels were rarely occluded with gel. Cell wall degradation led to the formation of stem cavities. Hyperplasia of xylem parenchyma was not seen.In Novada, fungal colonization remained low throughout the experiment. Macroscopic symptoms were absent except for longitudinal bursts in the stem, which appeared to be caused by hyperplasia of xylem parenchyma bordering infection. Vascular gelation occurred in the infected tissues, causing some vascular browning also. Xylem vessel regeneration was observed in the hyperplastic layer. Cavities were not formed, and wall discolouration was rare. Vascular gelation is considered part of theFusarium wilt resistance mechanism. It is followed by xylem vessel regeneration, which expresses a general plant response to vascular dysfunction rather than being part of the resistance mechanism.Although of different origin, vascular browning as such occurs in both susceptible and resistant interactions. In breeding for resistance, care should hence be taken with the current use of browning as an indication of disease.Samenvatting Anjers van de vatbare cultivar Early Sam en de resistente cultivar Novada werden geïnoculeerd met een conidiënsuspensie vanFusarium oxysporum f. sp.dianthi. Van beide cultivars werden regelmatig stengeldelen geoogst om deze microscopisch te onderzoeken en om de schimmelgroei te bepalen.Early Sam vertoonde de voor deze verwelkingsziekte kenmerkende symptomen en werd intensief gekoloniseerd. Aan het vaatweefsel waargenomen bruinkleuring bleek veroorzaakt te worden door verkleuring van de primaire wanden van geïnfecteerde vaten en de hen omringende cellen. Zelden trad er in de vaten gomvorming op. Celwandafbraak veroorzaakte de vorming van holten in de stengel. Hyperplasie van het houtparenchym werd niet waargenomen.In Novada bleef de schimmelgroei gedurende het hele experiment beperkt. Macroscopisch waren er enkel lengtescheuren in de stengel te zien, die veroorzaakt bleken te worden door hyperplasie van aan de infectie grenzend houtparenchym. In het geïnfecteerde vaatweefsel optredende gomvorming veroorzaakte ook enige bruinkleuring. In het hyperplastische weefsel werd regeneratie van houtvaten waargenomen. In de stengel werden geen holten gevormd, en verkleuring van de celwanden kwam weinig voor. De vorming van gommen in de houtvaten maakt waarschijnlijk deel uit van het resistentiemechanisme. De daarop volgende houtvatregeneratie is eerder een algemene reactie van de plant op vaatverstopping dan een deel van het resistentiemechanisme.Vaatverbruining, zij het van verschillende oorsprong, komt voor in zowel vatbare als resistente interacties. Om die reden moet men in de resistentieveredeling bij de anjer voorzichtig zijn met het gebruik van bruinkleuring als ziekteïndicatie.     

Biochemical properties of the pathogenesis-related proteins from tobacco

This review describes the discovery and identification of the pathogenesis-related proteins (PRs) from tobacco. In crude leaf extracts the PRs are distinguished from the proteins in uninfected plants by their solubility at pH 3, resistance to a range of proteases, and mobility in polyacrylamide gels upon electrophoresis (PAGE) in non-denaturing conditions. PAGE has been used as a qualitative and semi-quantitative assay for PRs, and their migration in gels made from different acrylamide concentrations has been used to identify charge and size isomers and electrophoretically identical PRs in different tobacco cultivars. The subunit composition and molecular weight (mol. wt) of the four PRs identified first in Xanthi-nc were determined by SDS-PAGE; staining the gels has shown that these same four proteins in Samsun NN did not contain carbohydrate, lipid or nucleic acid, nor were they isozymic forms of twenty five enzymes known to increase in activity following infection with TMV. Evidence suggests that most of the PRs in Xanthi-nc and Samsun NN are extracellular.The purification of several PRs from Xanthi-nc, Samsun NN and other tobaccos is described, as well as their mol. wt, subunit and amino acid composition. PRs 1a, b and c consist of a single polypeptide and have similar mol. wt and amino acid compositions. Antisera prepared against purified Xanthi-nc b₁ protein have been used to determine serological relationships between PRs and form the basis of a very sensitive quantitative assay using ELISA. The regulation of synthesis of some PRs has been shown to involve translational control.     

An improved method for extraction of sorghum polymeric protein complexes

A method for fractionating sorghum proteins using extraction solvents and techniques designed to obtain polymeric protein structures (especially disulfide linked) was developed. Extraction and separation conditions were optimized in terms of completeness of protein extraction, sample stability, and analytical resolution. After pre-extraction of albumins and globulins, a 3-step sequential procedure involving no reducing agents was applied to ground whole sorghum flour. The three fractions obtained represented proportionally different protein polymer contents and molecular weight distribution as evidenced by comparative size exclusion chromatography. Protein composition also varied among the extracts with differences in kafirin composition and non-kafirin proteins detected in the fractions by RP-HPLC and SDS-PAGE analysis. The ability to quantify and further characterize sorghum polymeric protein complexes will be useful for additional studies linking protein structures with functionality and digestibility and variations for these properties within diverse sorghum germplasm.     

Response of the soil fungal community to multi-factor environmental changes in a temperate forest

Both environmental and climatic changes are known to influence soil microbial biomes in terrestrial ecosystems. However, there are limited data defining the interactive effects of multi-factor environmental disturbances, including N-deposition, precipitation, and air temperature, on soil fungal communities in temperate forests. A 3-year outdoor pot experiment was conducted to examine the temporal shifts of soil fungal communities in a temperate forest following N-addition, precipitation and air temperature changes. The shifts in the structure and composition of soil fungal communities were characterized by denaturing gradient gel electrophoresis and DNA sequencing. N-addition regimen induced significant alterations in the composition of soil fungal communities, and this effect was different at both higher and lower altitudes. The response of the soil fungal community to N-addition was much stronger in precipitation-reduced soils compared to soils experiencing enhanced precipitation. The combined treatment of N-addition and reduced precipitation caused more pronounced changes in the lower altitude versus those in the higher one. Certain fungal species in the subphylum Pezizomycotina and Saccharomycotina distinctively responded to N fertilization and soil water control at both altitudes. Redundancy discrimination analysis showed that changes in environmental factors and soil physicochemical properties explained 43.7% of the total variability in the soil fungal community at this forest ecosystem. Variations in the soil fungal community were significantly related to the altitude, soil temperature, total soil N content (TN) and pH value (P < 0.05). We present evidence for the interactive effects of N-addition, water manipulation and air temperature to reshape soil fungal communities in the temperate forest. Our data could provide new insights into predicting the response of soil micro-ecosystem to climatic changes.     

Effect of dipeptide on intestinal peptide transporter 1 gene expression: An evaluation using primary cultured chicken intestinal epithelial cells

Peptide transporter 1 (PepT1) is a transporter responsible for absorbing dipeptide and tripeptide in enterocytes and is upregulated by dipeptide in mammals. It has not been certain whether intestinal PepT1 expression is responsive to dipeptides in chickens because of the lack of in vitro study using the cultured enterocytes. This study established a primary culture model of chicken intestinal epithelial cells (IECs) in two-dimensional monolayer culture using collagen gel by which the response of chicken PepT1 gene expression to dipeptide stimuli was evaluated. The cultured chicken IECs showed the epithelial-like morphology attached in a patch-manner and exhibited positive expression of cytokeratin and epithelial cadherin, specific marker proteins of epithelial cells. Moreover, the chicken IECs exhibited the gene expression of intestinal cell type-specific marker, villin1, mucin 2, and chromogranin A, suggesting that the cultured IECs were composed of enterocytes as well as goblet and enteroendocrine cells. PepT1 gene expression was significantly upregulated by synthetic dipeptide, glycyl-l-glutamine, in the cultured IECs. From the results, we herein suggested that dipeptide is a factor upregulating PepT1 gene expression in chicken IECs.     

双向电泳技术研究及其在农业生物蛋白质组学研究中的应用

双向电泳技术在蛋白质组学研究领域中处于核心地位。从样品制备、第一向等电聚焦电泳及第二向SDS-聚丙烯酰胺凝胶电泳、蛋白检测等关键环节方面对双向电泳技术的研究进展作了详细综述，并简要分析评价了以经典双向电泳为基础发展起来的差异凝胶电泳；同时重点介绍了双向电泳技术在农业生物蛋白质组学研究领域中的应用范围，为进一步开发利用提供参考；最后对双向电泳技术的发展前景作了展望。     

乌苏里拟鲿(Pseudobagrus ussuriensis)同工酶分析

采用聚丙烯酰胺凝胶电泳方法,对黑龙江水系乌苏里拟鲿(Pseudobagrus ussuriensis)心、肝、肾、眼、肌肉和性腺共6种组织进行了9种同工酶(ADH、EST、G6PDH、GDH、IDH、LDH、MDH、POD、SOD)的分析。结果表明,乌苏里拟鲿EST、GDH、IDH、POD同工酶谱中存在不同程度的组织特异性,EST表现出明显的性别差异性。共记录19个基因位点,多态位点百分数P=21.05%,种群遗传偏离指数d=-1,该乌苏里拟鲿种群内部杂合子缺失较严重,偏离Hardy-Weinberg平衡,遗传多样性较低。     

利用凝胶扩散法测定刺萼龙葵种子中β-甘露聚糖酶的活性

β-甘露聚糖酶是种子萌发过程中降解胚乳细胞壁的关键酶,明确其活性的动态变化可为揭示杂草种子的休眠萌发机制提供重要依据。以外来杂草刺萼龙葵Solanum rostratum Dunal种子为材料,建立了种子中β-甘露聚糖酶活性的检测方法—凝胶扩散法。利用凝胶扩散法对不同贮存时间及贮存条件下刺萼龙葵种子中β-甘露聚糖酶的活性进行了检测,发现贮存3年以上的种子中该酶的活性为0.03 nmol/(min·mg),显著低于贮存3年以下的种子中的酶活性0.15 nmol/(min·mg),而湿润冷藏的种子中β-甘露聚糖酶的活性为0.12 nmol/(min·mg),显著高于干燥冷藏的种子的酶活性0.02 nmol/(min·mg)。实际应用结果表明,凝胶扩散法综合了传统方法的优势,检测特异性强、灵敏度高、重复性好,可同时检测大量种子样品,具有良好的实用性。     

热碱致魔芋胶与黄原胶共混凝胶的显微结构与流变规律

【目的】探究魔芋胶与黄原胶混合溶胶体系在碱性条件下的凝胶形成机理与凝胶特性,为魔芋胶与黄原胶相关凝胶食品的开发提供理论依据。【方法】在总多糖浓度约为2.0%的条件下,配制不同黄原胶与魔芋胶比例的混合溶胶体系,添加2.0%的Na₂CO₃,并于90℃条件下恒温处理各溶胶体系2 h,冷却至室温后制得不同黄原胶与魔芋胶配比的复合凝胶。通过测定复合凝胶添加碳酸钠前后的凝胶破裂强度,揭示热碱处理对混合凝胶破裂强度的影响。分别测定去离子水浸泡、2.0%柠檬酸溶液浸泡以及冻融处理后凝胶破裂强度的变化情况,并结合扫描电镜观测凝胶的微观形貌,探究复合凝胶的凝胶特性。此外,通过流变学手段进一步研究黄原胶与魔芋胶复合凝胶网络的形成机制。【结果】在室温（20℃）条件下,非热碱处理的魔芋胶与黄原胶最佳协同比为5﹕5,热碱处理后的魔芋胶与黄原胶最佳协同比增加至7﹕3,原因可能是魔芋胶碱化后分子链上脱去部分乙酰基,形成分子间三维网络结构,但在随后的冷却过程中,与黄原胶协同结合位点减少,因此在达到最大协同比时,需要更多数目的魔芋胶分子参与。此外,经去离子水和2.0%柠檬酸溶液浸泡后,所有凝胶体系的破裂强度都有所降低,其中经过2.0%柠檬酸溶液浸泡后的凝胶破裂强度下降更为明显。冻融处理后,复合凝胶均出现明显的析水现象,魔芋胶比例越高,析水现象越明显。进一步探究魔芋胶与黄原胶共混体系在2.0% Na₂CO₃浓度、90℃条件下的凝胶化过程,发现随黄原胶添加量增加,凝胶化速率呈减小趋势。此外,凝胶弹性模量在90—60℃呈降低趋势,60℃以下逐渐上升。【结论】在90℃条件下碱处理魔芋胶与黄原胶共混体系时,诱导体系形成热不可逆凝胶。当降低该体系的温度时,黄原胶分子在60℃时开始与魔芋胶网络结合,增加了凝胶的弹性模量。当魔芋胶与黄原胶比例为7﹕3时,室温下混合凝胶的破裂强度最大。经去离子水和2.0%柠檬酸溶液浸泡后,凝胶强度均有所降低。魔芋胶与黄原胶形成的复合凝胶在一定条件下可以改善单纯碱法诱导的魔芋胶凝胶析水多、强度差等缺点。