安徽马尾松人工林营养元素分配格局的研究

本文系统地研究了马尾松人工林营养元素的分配格局。结果表明马尾松不同器官营养元素含量是叶>枝皮>干皮>枝木>干木;同化器官——针叶中营养元素含量规律为N>K>Ca>Mg>P,非同化器官为Ca>N>K>Mg>P;不同器官营养元素的贮量为干木>干皮>叶>枝木>枝皮,同化器官对不同营养元素的贮量呈N>K>Ca>Mg>P,非同化器官为Ca>N>K>Mg>P;不同立地条件下,马尾松林生产1t干物质所贮存的营养元素不同,立地条件愈好,营养元素效率愈高,贮存愈少;母岩、土层厚度和养分总量是影响马尾松林地上各器官,特别是针叶营养元素含量的重要因子,土壤N、P含量越高,马尾松人工林生物量越大。     

苦豆子提取物与埃玛菌素混用对小菜蛾生长发育和繁殖的影响

将苦豆子甲醇和水提取物分别与埃玛菌素混合,在室内测定了两混合物对小菜蛾生长发育和繁殖的影响.结果表明:苦豆子甲醇提取物 埃玛菌素和苦豆子水提取物 埃玛菌素对小菜蛾3龄幼虫口服毒力明显高于埃玛菌素,其LC50值分别为0.19、0.32和0.51 mg.L-1;用两混合物以及埃玛菌素亚致死剂量处理3龄幼虫,试虫化蛹率、羽化率和成虫的繁殖力均呈现明显不良影响.     

土壤水分时间稳定性研究进展

土壤水分是陆地生态系统中不可或缺的组成部分,在地表水文过程中起着关键作用,连接着一系列的水文、生态、气候和地质学过程,是陆地生态系统健康运行的关键。以土壤水分时间稳定性概念为主线,从时间稳定性概念、研究方法、应用和影响因素等方面,系统阐述了土壤水分时间稳定性近年来的研究进展,探讨了代表性测点的选取标准以及土壤水分时间稳定性的影响因素。结合目前的研究进展,提出了未来的研究重点:加强多因素综合作用对土壤水分时间稳定性的研究;结合"3S"技术、计算机模拟和野外实测来研究时间稳定性的尺度问题;如何高效选择代表性测点;探讨时间稳定性概念在植被恢复区和气候敏感区的研究与应用。     

禁牧条件下不同类型草地群落结构特征

利用幂乘方法则模型探讨了鄂尔多斯3种不同类型草地在禁牧情况下的群落结构特征,包括物种组成、物种多样性、生物量和空间分布规律。结果表明:幂乘方法则在解析鄂尔多斯不同类型草地的空间异质性时具有很好的吻合性;羊草(Leymuschinensis)草地、芨芨草(Achnatherum splendens)草地和油蒿(Artemisia ordosica)灌丛草地均比随机分布呈现了较强的空间异质性,群落整体的空间异质性指数表现为油蒿灌丛草地>羊草草地>芨芨草草地;群落整体的物种多样性指数为油蒿灌丛草地>羊草草地>芨芨草草地;L-样方(50cm×50cm)内的平均物种数和物种多样性指数均表现为羊草草地极显著地高于油蒿灌丛草地,油蒿灌丛草地又极显著地高于芨芨草草地(P<0.001);L-样方内的平均生物量表现为油蒿灌丛草地极显著地高于芨芨草草地(P<0.001),而羊草草地与油蒿灌丛草地以及芨芨草草地之间没有显著性差异;这3种类型的草地其L-样方内的平均生物量和物种多样性指数都随着群落整体空间异质性指数的增大而增大。     

Structure of Novel Enzyme in Mannan Biodegradation Process 4-O-β-d-Mannosyl-d-Glucose Phosphorylase MGP

The crystal structure of a novel component of the mannan biodegradation system, 4-O-β-d-mannosyl-d-glucose phosphorylase (MGP), was determined to a 1.68-Å resolution. The structure of the enzyme revealed a unique homohexameric structure, which was formed by using two helices attached to the N-terminus and C-terminus as a tab for sticking between subunits. The structures of MGP complexes with genuine substrates, 4-O-β-d-mannosyl-d-glucose and phosphate, and the product d-mannose-1-phosphate were also determined. The complex structures revealed that the invariant residue Asp131, which is supposed to be the general acid/base, did not exist close to the glycosidic Glc-O4 atom, which should be protonated in the catalytic reaction. Also, no solvent molecule that might mediate a proton transfer from Asp131 was observed in the substrate complex structure, suggesting that the catalytic mechanism of MGP is different from those of known disaccharide phosphorylases.     

Helicobacter pylori recrudescence and its influencing factors

Helicobacter pylori (H pylori) is known as one of the most common infectious pathogens, with high infection and recurrence rates worldwide. The prevalence of H pylori is up to 90% in developing countries, while the annual recurrence rate is much higher than that in developed countries. Recurrence can occur either by recrudescence or reinfection. Compared with reinfection, the time window for recrudescence is generally shorter, followed by the recurrence of H pylori–associated diseases in the short‐term. Many factors are involved in the H pylori reinfection, such as the prevalence of H pylori infection, living conditions and economic development, health conditions and so forth. Previous studies focused less on H pylori recrudescence. Therefore, the influencing factors for H pylori recrudescence needed further exploration. This study reviewed the recrudescence of H pylori infection and its influencing factors.     

濒危药用植物桃儿七的离体培养研究

以桃儿七种子诱导的无菌苗为材料,研究了外源激素对芽诱导、增殖和生根的影响,建立了桃儿七离体培养再生体系。结果表明：芽诱导阶段,采用3.0 mg·L^-1 6-BA+0.5 mg·L^-1 GA₃激素组合,出芽率最高可达85-71%,缩短出芽时间30~40 d,在添加3.0 mg·L^-1 6-BA+0.2 mg·L^-1 IAA的MS培养基上利于增殖,增殖速度快,增殖系数1.63。以WPM+1.5 mg·L^-1 IAA+0.5 mg·L^-1 NAA的培养基培养30 d 后,生根率可达60.1%。     

Methylation protects miRNAs and siRNAs from a 3'-end uridylation activity in Arabidopsis

Small RNAs of 21-25 nucleotides (nt), including small interfering RNAs (siRNAs) and microRNAs (miRNAs), act as guide RNAs to silence target-gene expression in a sequence-specific manner. In addition to a Dicer homolog, DCL1, the biogenesis of miRNAs in Arabidopsis requires another protein, HEN1. miRNAs are reduced in abundance and increased in size in hen1 mutants. We found that HEN1 is a miRNA methyltransferase that adds a methyl group to the 3'-most nucleotide of miRNAs, but the role of miRNA methylation was unknown. Here, we show that siRNAs from sense transgenes, hairpin transgenes, and transposons or repeat sequences, as well as a new class of siRNAs known as trans-acting siRNAs, are also methylated in vivo by HEN1. In addition, we show that the size increase of small RNAs in the hen1-1 mutant is due to the addition of one to five U residues to the 3' ends of the small RNAs. Therefore, a novel uridylation activity targets the 3' ends of unmethylated miRNAs and siRNAs in hen1 mutants. We conclude that 3'-end methylation is a common step in miRNA and siRNA metabolism and likely protects the 3' ends of the small RNAs from the uridylation activity.     

华根霉固态与液态培养产胞外蛋白的比较蛋白质组学分析

【目的】考察固态和液态两种培养方式对丝状真菌华根霉(Rhizopus chinensis)CCTCC M201021产胞外蛋白的影响,以加深对微生物固、液态培养特异性产酶的认识。【方法】利用成分相同的培养基对华根霉分别进行平板固态培养和液态培养,提取华根霉所产胞外蛋白,采用二维凝胶电泳(2-DE)结合质谱分析,分离鉴定差异蛋白。【结果】固态培养下华根霉所产胞外蛋白的蛋白酶活性是液态培养的9.2倍。胞外蛋白质组数据分析表明,华根霉固态和液态培养所产胞外蛋白存在显著差异,其中约70%是固态和液态培养下各自产生的特有蛋白。质谱鉴定进一步表明,固、液态培养对华根霉产胞外蛋白的种类和表达量都有显著影响,其中水解酶类所占比例较大,主要是与蛋白质降解相关的蛋白。【结论】固态和液态不同培养方式影响了华根霉产胞外蛋白的组成,有些基因只在特定培养方式下表达。固态培养下华根霉产胞外蛋白酶种类相对更多以及大部分蛋白酶的上调表达,可能是固态培养下胞外蛋白酶活性很高的原因。研究结果提示需要注意固液态不同培养方式下丝状真菌胞外酶的筛选和生产可能存在的不一致性。     

微波辅助提取荷叶生物碱条件的优化

对荷叶中主要生理活性物质生物碱的提取条件进行了初步研究,以稀盐酸水为溶剂结合微波照射浸渍提取,获得了较优化的提取工艺,即用pH2.5 HCl、微波辅助处理2.5 min、固液比1:40、提取温度90℃、提取时间3 h,可得荷叶生物碱量172.63μg.g-1。