北美水貂和欧亚水獭在东北地区的分布与生态位重叠

作为入侵物种,北美水貂(Neovison vison)在欧洲引起了一系列生态问题,侵占了欧亚水獭(Lutra lutra)的生态空间,其入侵性对当地生物多样性和生态系统构成了严重威胁。水貂引入我国东北地区已有70多年的历史,然而国内对其野外种群却鲜有研究。掌握水貂种群的入侵范围、入侵影响因素以及与本地具有相似生态位的欧亚水獭之间的竞争关系,对水貂的入侵管理和东北地区的生物多样性保护具有重要意义。本研究利用实地调查和文献资料获取的分布信息,通过集合模型识别水貂和水獭的潜在分布区,评估水貂对水獭在地理空间上的入侵风险,并通过主成分分析(principal component analysis,PCA)评估其生态位重叠和影响因素。结果表明:(1)我国东北地区水貂的潜在分布区面积为61,944.57 km²,水獭的潜在分布区面积为83,590.94 km²,两者重叠区域面积为50,544.21 km²,占水獭潜在分布区面积的60.47%;(2)从各省分布情况来看,黑龙江省水獭受水貂入侵的风险最高,潜在分布区重叠的比例达到78.9...     

Low genetic diversity and population connectivity fuel vulnerability to climate change for the Tertiary relict pine Pinus bungeana

Endemic species are important components of regional biodiversity and hold the key to understanding local adaptation and evolutionary processes that shape species distributions. This study investigated the biogeographic history of a relict conifer Pinus bungeana Zucc. ex Endl. confined to central China. We examined genetic diversity in P. bungeana using genotyping-by-sequencing and chloroplast and mitochondrial DNA markers. We performed spatial and temporal inference of recent genetic and demographic changes, and dissected the impacts of geography and environmental gradients on population differentiation. We then projected P. bungeana's risk of decline under future climates. We found extremely low nucleotide diversity (average π 0.0014), and strong population structure (global F_ST 0.234) even at regional scales, reflecting long-term isolation in small populations. The species experienced severe bottlenecks in the early Pliocene and continued to decline in the Pleistocene in the western distribution, whereas the east expanded recently. Local adaptation played a small (8%) but significant role in population diversity. Low genetic diversity in fragmented populations makes the species highly vulnerable to climate change, particularly in marginal and relict populations. We suggest that conservation efforts should focus on enhancing gene pool and population growth through assisted migration within each genetic cluster to reduce the risk of further genetic drift and extinction.     

Structural studies of the capsular polysaccharide and lipopolysaccharide O-antigen of Aeromonas salmonicida strain 80204-1 produced under in vitro and in vivo growth conditions.

Aeromonas salmonicida is a pathogenic aquatic bacterium and the causal agent of furunculosis in salmon. In the course of this study, it was found that when grown in vitro on tryptic soy agar, A. salmonicida strain 80204-1 produced a capsular polysaccharide with the identical structure to that of the lipopolysaccharide O-chain polysaccharide. A combination of 1D and 2D NMR methods, including a series of 1D analogues of 3D experiments, together with capillary electrophoresis-electrospray MS (CE-ES-MS), compositional and methylation analyses and specific modifications was used to determine the structure of these polysaccharides. Both polymers were shown to be composed of linear trisaccharide repeating units consisting of 2-acetamido-2-deoxy-D-galacturonic acid (GalNAcA), 3-[(N-acetyl-L-alanyl)amido]-3,6-dideoxy-D-glucose[3-[(N-acetyl-L-alanyl)amido]-3-deoxy-D-quinovose, Qui3NAlaNAc] and 2-acetamido-2,6-dideoxy-D-glucose (2-acetamido-2-deoxy-D-quinovose, QuiNAc) and having the following structure: [-->3)-alpha-D-GalpNAcA-(1-->3)-beta-D-QuipNAc-(1-->4)-beta-D-Quip3NAlaNAc-(1-]n, where GalNAcA is partly presented as an amide and AlaNAc represents N-acetyl-L-alanyl group. CE-ES-MS analysis of CPS and O-chain polysaccharide confirmed that 40% of GalNAcA was present in the amide form. Direct CE-ES-MS/MS analysis of in vivo cultured cells confirmed the formation of a novel polysaccharide, a structure also formed in vitro, which was previously undetectable in bacterial cells grown within implants in fish, and in which GalNAcA was fully amidated.     

贺兰山不同生境旱生灌木的解剖学研究

贺兰山荒漠地带三种不同基质生境的２０种旱生灌木的营养器官的比较解剖学研究表明：其共同特点是叶片的表面积／体积的比值小,叶表具厚的角质层、表皮毛,气孔下陷、并具孔下室,叶向中栅栏组织发达;轴器官中木栓层细胞层数多,皮层较厚,机械组织发达,木薄壁组织及髓部细胞的细胞壁术化加厚,根内都具周皮、木质部的导管分子大小不一、频率较高。此外,根、茎、叶中普遍存在粘液细胞和草酸钙结晶,部分植物的根和茎内有异常维管组织。这些结构特征都与早生环境相关,而不同基质生境中生长的植物尚存在一定差异。     

植物蛋白质S-亚硝基化修饰的检测与分析

S-亚硝基化是一种重要的蛋白质翻译后修饰方式, 是指一氧化氮(NO)基团共价连接至靶蛋白特定半胱氨酸残基的自由巯基, 从而形成S-亚硝基硫醇(SNO)的过程。S-亚硝基化修饰广泛存在于各有机体中, 通过改变蛋白质生化活性、稳定性、亚细胞定位以及蛋白质-蛋白质相互作用等机制而调控不同的生物学过程或信号通路。在蛋白质S-亚硝基化检测分析方法中, 最为广泛使用的是生物素转化法(biotin switch assay), 其基本原理是首先封闭未被修饰的自由巯基, 进而将被修饰的SNO基团特异地还原为自由巯基并使用生物素将其特异标记。被生物素标记的半胱氨酸残基(即被修饰位点)可进一步通过蛋白质免疫印迹和/或质谱等方法进行检测分析。该文详细描述了植物蛋白质样品的体内和体外生物素转化法的实验流程, 并对实验过程中的注意事项进行了讨论。     

Induction of the second exopolysaccharide (EPSb) in Rhizobium meliloti SU47 by low phosphate concentrations.

In previous work, Rhizobium meliloti SU47 produced its alternative exopolysaccharide (EPSb [also called EPS II]) only in strains that were genetically altered to activate EPSb synthesis. Here we report that EPSb synthesis is not entirely cryptic but occurred under conditions of limiting phosphate. This was shown in several different exo mutants that are blocked in the synthesis of the normal exopolysaccharide, succinoglycan. In addition, EPSb biosynthetic gene expression was markedly increased by limiting phosphate. An apparent regulatory mutant that does not express alkaline phosphatase activity was unable to produce EPSb under these conditions. A mucR mutant that was previously shown to produce EPSb instead of the normal exopolysaccharide, succinoglycan, was not sensitive to phosphate inhibition of EPSb synthesis. No evidence was found to indicate that exoX, which affects succinoglycan synthesis, had any influence on EPSb synthesis. In contrast to limiting phosphate, limiting nitrogen or sulfur did not stimulate EPSb synthesis as it does succinoglycan.     

小黑杨花粉植株H_1株系间变异及其选择利用的研究

小黑杨(Populus xiaohei T.S.Hwang ex C.Wang et Tung)花药离体培养获得单倍体植株,经14年的生长观察,发现花粉植株间表现出明显分离。选出19个株系进行田间比较试验,统计分析,结果发现材积生长差异显著。可从中选出优良株系加以利用,并提出杨树单倍体育种程序。     

Functional and evolutionary relatedness of genes for exopolysaccharide synthesis in Rhizobium meliloti and Rhizobium sp. strain NGR234.

Rhizobium meliloti SU47 and Rhizobium sp. strain NGR234 produce distinct exopolysaccharides that have some similarities in structure. R. meliloti has a narrow host range, whereas Rhizobium strain NGR234 has a very broad host range. In cross-species complementation and hybridization experiments, we found that several of the genes required for the production of the two polysaccharides were functionally interchangeable and similar in evolutionary origin. NGR234 exoC and exoY corresponded to R. meliloti exoB and exoF, respectively. NGR234 exoD was found to be an operon that included genes equivalent to exoM, exoA, and exoL in R. meliloti. Complementation of R. meliloti exoP, -N, and -G by NGR234 R'3222 indicated that additional equivalent genes remain to be found on the R-prime. We were not able to complement NGR234 exoB with R. meliloti DNA. In addition to functional and evolutionary equivalence of individual genes, the general organization of the exo regions was similar between the two species. It is likely that the same ancestral genes were used in the evolution of both exopolysaccharide biosynthetic pathways and probably of pathways in other species as well.