Effect of coenzymes on the quaternary structure conformation of glyceraldehyde-3-phosphate dehydrogenases of mung beans and rabbit muscle.

Kinetics of thermal inactivation of glyceraldehyde-3-phosphate dehydrogenases of mung beans and rabbit muscle have been studied under different pH conditions in the absence and presence of various concentrations of NAD+ and NADH. The data have been discussed with respect to the effect of the coenzymes on the quaternary structure symmetry of the two enzymes and their binding isotherms. Both the (homo-tetrameric) apo-enzymes exhibit biphasic kinetics of thermal inactivation, characteristic of C2 symmetry, at lower pH values and a single exponential decay of enzyme activity, characteristic of D2 symmetry, at higher pHs. In each case, NAD+ has no effect on the biphasic kinetic pattern of thermal inactivation at lower pH values, but NADH brings about a change to single exponential decay. At higher pH values, NADH does not affect the kinetic pattern (single exponential decay) of any enzyme, but NAD+ alters it to biphasic kinetics in each case. The data suggest that NAD+ and NADH have higher affinity for the C2 and D2 symmetry conformation, respectively. With mung beans enzyme, the effect of NAD+ on the two rate constants of biphasic inactivation at pH 7.3 is consistent with a Kdiss equal to 110 microM. The NAD(+)-dependent changes in the kinetic pattern of thermal inactivation of this enzyme at pH 8.6 suggest a positive cooperativity in the coenzyme binding (nH = 3.0). In the binding of NADH to the mung beans enzyme, a weak positive cooperativity is observed at pH 7.3.(ABSTRACT TRUNCATED AT 250 WORDS)     

SNP discovery from next-generation transcriptome sequencing data and their validation using KASP assay in wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.)

Single nucleotide polymorphisms (SNPs) are becoming the most amenable form of DNA-based molecular markers for genetic analysis. In hexaploid bread wheat (Triticum aestivum L.), it is difficult to discern true polymorphic SNPs due to homoeologous and paralogous genes. Two serial analysis of gene expression (SAGE) libraries were developed utilizing leaves from resistant plants carrying leaf rust resistance gene Lr28; one library was derived from leaves that were mock inoculated and the other was derived from leaves inoculated with the urediniospores of the leaf rust pathogen Puccinia triticina. Next-generation sequencing reads, after quality trimming and removal of fungal sequences, were mapped to wheat reference sequences at Ensembl Plants. CLC Genomics Workbench and Freebayes softwares were employed for SNP calling. A total of 611 SNPs were predicted to be common by both softwares, of which 207 varietal SNPs were identified by ConservedPrimer software. A subset of 100 SNPs was used for validation across 47 wheat genotypes using Kompetitive Allele Specific PCR (KASP) assay; 83 SNPs could be successfully validated. These SNPs were positioned on wheat subgenomes and chromosome arms. When functionally annotated, many sequences harboring SNPs showed homology to resistance and resistance-like genes listed in Plant Resistance Gene database (PRGdb) as well as pathogenesis-related (PR) and stress-responsive genes. The results of the present study involving discovery of SNPs associated with resistance to leaf rust, a major threat to wheat production worldwide, will be valuable for molecular breeding for rust resistance.     

Transacetylation of carbohydrates in organic solvent catalysed by O-acetylpeptidoglycan esterase from Neisseria gonorrhoeae

The potential of the Neisseria gonorrhoeae O-acetylpeptidoglycan esterase (Ape1a) for catalysing transacetylations in organic solvents with a number of carbohydrate acceptors was investigated. The performance of the enzyme was observed to improve as the polarity index of the solvent increased. The best transacetylation conditions were determined to be a 1:6 phosphate buffer/ethyl acetate system, where Ape1a catalysed approximately 28% acetylation of 4-methylumbelliferyl-N-acetylglucosamine using p-nitrophenyl acetate as donor. Further analysis of the acetylated products by reverse phase HPLC and ESI-mass spectrometry confirmed the presence of monoacetylated 4-methylumbelliferyl-N-acetylglucosamine. Under identical reaction conditions, the enzyme also performed transacetylations using ethyl acetate or vinyl acetate as donor. These results demonstrated the feasibility of using the bacterial cell wall enzyme Ape1a to generate hitherto unattainable compounds which may be used as antagonists of peptidoglycan-metabolizing enzymes.     

基于地统计学的新疆棉田烟粉虱(Bemisia tabaci (Gennadius))危害动态与时空分布

应用地统计学(GS)的原理与方法研究了外来入侵有害生物烟粉虱(Bemisia tabaci (Gennadius))为害新疆棉田的时空动态,并与经典统计学进行对比分析.两种方法一致表明,烟粉虱成虫在空间上呈聚集分布的格局,而各时期成虫的聚集程度依据空间变异随机程度所占的比例不同而不同.经频次分布检验,以零频率法参数拟合的负二项分布来表达其空间分布型最为合适.运用GS的分析方法,进一步得到种群分布面积变化与扩散的趋势,并依此对昆虫种群的扩散模型进行模拟.棉田烟粉虱成虫在田间7～8月份均存在一定的空间相关性,随机程度为19.22%～49.99%;空间相关距离(相关程)在一个月内从32m急速增至6372m,随后在2000～3000m的范围波动.从整个发生过程看出,烟粉虱从越冬场所顺风侵入大田后,迁飞扩散在很大程度上受风向的影响,属于典型的借助风力扩散的昆虫,其在棉田的垂直分布则与吐鲁番地区独特的暖温带大陆性干旱荒漠气候特征有关.顺风扩散时多从棉株上部叶片开始危害, 而逆风扩散时从棉株中、下部叶片危害.烟粉虱在棉株上建立稳定种群后,中、下部虫口密度要略高于上部, 这是烟粉虱对吐鲁番地区特殊气候的适应.     

土地整理项目区的景观格局及其生态效应

目前项目角度的土地整理生态效应评价较少,受到研究幅度的制约,而且已有研究中对景观格局优化目标和生态效应的系统分析较少.选择典型的土地整理项目作为研究案例,以GIS和景观指数为研究手段,结合景观格局优化目标建立相应的指标体系,对土地整理的生态效应进行评价.研究表明,土地整理项目的生态效应指标体系包括提升生物多样性、维持物质和能量流通、维持景观格局稳定、提升生活环境品质、提高生态服务价值等5个方面.研究区土地整理具有正效应和负效应,最大斑块面积提高、斑块密度减少、聚集度提高、廊道宽度和连通度提高、缓冲区宽度增加、植被覆盖增加、合理功能分区是土地整理的正效应,而景观多样性降低、分维数减少和生态服务价值降低是其负效应.因此,在土地整理规划和设计时应融入景观设计和生态保育思想.     

Nutrient enrichment increases plant biomass and exotic plant proportional cover independent of warming in freshwater wetland communities

Anthropogenic environmental change can increase exotic species performance and reduce native biodiversity. Nutrient enrichment may favor exotic plants with higher growth rates. Warming may increase the performance of exotic species from warmer native ranges and/or decrease the performance of locally adapted native species. However, community level impacts of nutrient enrichment and warming may depend on their combined effects on individual species and species interactions. We conducted a factorial 11-month field experiment that manipulated 1) plant origin: native, exotic (species from warmer and nutrient rich habitats), or native-&-exotic; 2) nutrients: ambient or high; and 3) temperature: ambient, +1 °C, or +2 °C. Elevated nutrients increased biomass and exotic plant proportional cover. Exotic diversity was higher with elevated nutrients. Native and exotic biomass responses to elevated nutrients were smaller in native-&-exotic treatments. Elevated nutrients increased the relative abundance of two exotic and decreased one exotic and three native species in native-&-exotic treatments. The predicted exotic to native biomass ratio was higher than the observed ratio, indicating that native plants reduced the potential growth of exotic plants in native-&-exotic treatments. Warming had no effect on plant biomass or diversity. These results suggest that nutrient enrichment increases the performance of some exotic plants and that it is critical to consider native and exotic plant interactions when assessing anthropogenic factor and exotic plant effects on native plant communities.     

Exploration of the binding affinities between ecdysone agonists and EcR/USP by docking and MM-PB/GBSA approaches

Ecdysone receptor (EcR) is a significant target in the identification of new environmentally friendly pesticides. There are two types of ecdysone agonists: steroidal ecdysone agonists and dibenzoylhydrazines (DBHs). In this study, various modeling methods (homology modeling, molecular docking, MD simulation, binding free energy calculation, and per-residue binding free energy decomposition) were utilized to study the different binding mechanisms of two types of ecdysone agonists. Our theoretical results indicated that the relative binding potencies of DBHs can be ranked sufficiently accurately using the MOE docking method. However, MM/PBSA calculations more accurately predicted the binding affinities between steroidal ecdysone agonists and EcR-LBD. To identify the key residues involved in ecdysone agonist binding, the binding free energy (ΔG _Bind) was decomposed into the energy contributions of individual residues. The results revealed that nine residues—Ile339, Thr343, Met380, Met381, Tyr403, Tyr408, Asp419, Gln503, and Asn504—determined the binding affinities of the DBHs. Glu309, Met342, Arg383, Arg387, and Leu396 were important influences on the binding affinities of the steroidal ecdysone agonists.

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Graphical abstract The ecdysone receptor (EcR) is related to insect growth and has been shown to be a useful target for insecticides