甘草高效根瘤菌菌株筛选试验研究

采用室内水培法,研究了10株甘草根瘤菌对红皮和黄皮甘草的接种效果。结果表明:接种根瘤菌后的甘草各项生长性状均有不同程度改善,综合地上干重、地下主根干重、根瘤数量及结瘤率等技术指标,筛选出不同甘草品种最佳匹配的根瘤菌菌株,即红皮甘草与菌株R367,黄皮甘草与菌株R172的亲合力最高, R367、R172为筛选的高效根瘤菌菌株。     

Molecular characterization of H1N1 influenza A viruses from human cases in North America

Subtypes of H1N1 influenza virus can be found in humans in North America, while they are also associated with the infection of swine. Characterization of the genotypes of viral strains in human populations is important to understand the source and distribution of viral strains. Genomic and protein sequences of 10 isolates of the 2009 outbreak of influenza A （H1N1） virus in North America were obtained from GenBank database. To characterize the genotypes of these viruses, phylogenetic trees of genes PB2, PB1, PA, HA, NP, NA, NS and M were constructed by Phylip3.67 program and N-Linked glycosylation sites of HA, NA, PB2, NS1 and M2 proteins were analyzed online by NetNGlyc1.0 program. Phylogenetic analysis indicated that these isolates are virtually identical but may be recombinant viruses because their genomic fragments come from different viruses. The isolates also contain a characteristic lowly pathogenic amino acid motif at their HA cleavage sites （IPSIQSR↓GL）, and an E residue at position 627 of the PB2 protein which shows its high affinity to humans. The homologous model of M proteins showed that the viruses had obtained the ability of anti-amantadine due to the mutation at the drug-sensitive site, while sequence analysis of NA proteins indicated that the viruses are still susceptible to the neuraminidase inhibitor drug （i.e. oseltamivir and zanamivir） because no mutations have been observed. Our results strongly suggested that the viruses responsible for the 2009 outbreaks of influenza A （H1N1） virus have the ability to cross species barriers to infect human and mammalian animals based on molecular analysis. These findings may further facilitate the therapy and prevention of possible transmission from North America to other countries.     

Green fluorescent protein （GFP） as a vital marker for studying the interaction of Phytophthora sojae and soybean

Transgenic Phytophthora sojae strains that produce green fluorescent protein （GFP） were obtained after stable DNA integration using the Hsp70 promoter and the Ham34 terminator of Bremia lactucae. The expression of GFP during different developmental stages of P. sojae was observed using fluorescent microscopy. Based on this reporter system, the histopathologic events caused by the pathogen in soybean leaves, hypocotyls and roots were monitored. Meanwhile, the difference in resistance between different soybean cultivars against P. sojae was analyzed microscopically in roots. The results indicate that GFP can be stably expressed in zoosporangia, zoospores, cysts, hyphae and oospores of P. sojae. Using the GFP marker, the infecting pathogens in leaves, hypocotyls and roots of host could be distinctly visualized. The germ tube length of cysts germinating on the roots of resistant cultivar Nannong 8848 was longer than that on the roots of susceptible cultivar Hefeng 35. These results show for the first time that this eukaryotic reporter can be used in P. sojae as a stable and vital marker, allowing the study of genetics of this hemibiotrophic pathogen.     

Comparison of the carbon isotope composition of total organic carbon and long-chain <Emphasis Type="Italic">n</Emphasis>-alkanes from surface soils in eastern China and their significance

Surface soil samples collected over a high spatial resolution in eastern China were analyzed for carbon isotope composition （δ^13C） of total organic carbon （TOC） and higher plant-derived long-chain n-alkanes, with the latter reported as weighted mean values. The two sets of δ^13C values are significantly correlated and show similar trends in spatial variation. The spatial distribution of δ^13C shows less negative values in the mid-latitudes between 31°N and 40°N and more negative ones at higher and lower latitudes. This is consistent with previously reported carbon isotope data from surface soil phytoliths in the same region and suggests that the mid-latitude area provides relatively favorable growing condi- tions for C4 plants. Furthermore, δ^13C values of both TOC and long-chain n-alkanes from 12 surface soil samples collected from a small grassland in north China displayed similar carbon isotope values and the difference between paired δ^13C of a soil samples remains relatively constant. Our data demonstrate that in eastern China, soil δ^13C composition of both TOC and long-chain n-alkanes is effective indicators of C3/C4 ratios of the prevailing vegetation. This work suggests that -22‰ and -32‰ are good es- timated end members for the weighted mean δ^13C values of long-chain n-alkanes （C27, C29 and C31 n-alkanes） from soils under dominant C4 or C3 vegetation, allowing us to reconstruct paleovegetation trends.     

The role of β18-β19 loop structure in insecticidal activity of Cry1Ac toxin from Bacillus thuringiensis

The β18-β19 loop in domain Ⅲ of Cry1Ac toxin is unique among Bacillus thuringlensis Cry proteins. In this study, the role of the loop structure in insecticidal activity of Cry1Ac toxin was investigated. Alanine scanning mutations within the loop were initially generated and most mutants were over-expressed and reduced toxicity at different degrees, except mutant N546A that showed almost 2 times enhanced toxicity against Helicoverpa armigera larvae. Further mutagenic analysis of N546 revealed that a charged amino acid in this position would cause very unfavorable influence on insecticidal activity. In addition, the deletion of N546 led to protein instability because of destruction of the loop integrity. Besides, mutant W544F was much more toxic than W544Y, indicating that hydrophobic nature of the position was important for maintaining the stability and activity of Cry1Ac protein. These findings are the first biological evidence for a structural function of β18-β19 loop in insecticidal activity of the Cry1Ac toxin.     

Genome evolution of novel influenza A （H1N1 ） viruses in humans

The epidemic situation of A H1N1 flu arose in North America in April 2009, which rapidly expanded to three continents of Europe, Asia and Africa, with the risk ranking up to 5. Until May 13th, the flu virus of A H1N1 had spread into 33 countries and regions, with a laboratory confirmed case number of 5728, including 61 deaths. Based on IRV and EpiFluDB database, 425 parts of A H1N1 flu virus sequence were achieved, followed by sequenced comparison and evolution analysis. The results showed that the current predominant A H1N1 flu virus was a kind of triple reassortment A flu virus： （i） HA, NA, MP, NP and NS originated from swine influenza virus; PB2 and PA originated from bird influenza virus; PB1 originated from human influenza virus. （ii） The origin of swine influenza virus could be subdivided as follows： HA, NP and NS originated from classic swine influenza virus of H1N1 subtype; NA and MP originated from bird origin swine influenza virus of H1N1 subtype. （iii） A H1N1 flu virus experienced no significant mutation during the epidemic spread, accompanied with no reassortment of the virus genome. In the paper, the region of the representative strains for sequence analysis （A/California/04/2009 （H1N1） and A/Mexico/4486/2009 （H1N1）） included USA and Mexico and was relatively wide, which suggested that the analysis results were convincing.     

膜荚黄芪根瘤菌DNA的G+Cmol%测定及DNA-DNA杂交

在数值分类的基础上,利用复性速率液相分子杂交法及热变性温度法(Tm)对采自甘肃的膜荚黄芪根瘤菌进行了DNA-DNA杂交及G+Cmol%测定.结果表明,待测菌株的之间的DNA同源性大于70%,而与参比菌株的DNA同源性均低于70%;G+C mol%为63.7%.表明此新群为1个不同于已知种的、独立的DNA同源群.     

接种AMF及施氮对滨海盐土氮矿化的影响

【目的】研究接种丛枝菌根真菌(arbuscular mycorrhizal fungi,AMF)以及施氮对滨海盐土氮素转化的影响,探究提高滨海盐土氮素供应能力的有效途径。【方法】以江苏北部滨海盐土为研究对象,采用室内培养试验方法,研究接种AMF以及不同施氮水平处理对土壤氮素矿化和氮素供给的影响。【结果】施氮对菌根侵染率具有显著促进作用(P<0.05),低氮处理(N1,施氮量为92 mg/kg)菌根侵染率达45.22%,显著高于高氮处理(N2,施氮量为184 mg/kg)的32.44%,而不施氮处理(N0)菌根侵染率仅有16.00%。在接种AMF 1 d时,低氮处理的滨海盐土铵态氮含量显著低于高氮和不施氮处理的滨海盐土(P<0.05),说明较高的菌根侵染率更有利于植物对铵态氮的吸收与同化,施氮及接种处理显著影响了滨海盐土的氨化过程(P<0.05),但并未对其产生交互作用。硝态氮含量随施氮量的增加而升高,除培养5和10 d外,其余时间点高氮处理滨海盐土的硝态氮含量显著高于低氮以及不施氮处理(P<0.05)的滨海盐土,硝化作用受施氮和接种AMF的交互作用影响。滨海盐土净氮矿化量以及净氮矿化速率在施氮处理和接种处理下差异均不显著(P>0.05),但交互作用对其产生了极显著促进作用(P<0.001)。【结论】对于滨海盐土,添加过多的氮反而抑制丛枝菌根真菌与耐盐植物共生关系的建立;施氮有利于提高滨海盐土的氮矿化作用,施氮量过高并不能对其供氮能力产生促进作用;丛枝菌根真菌与植物共生关系的建立能有效提高氮肥利用效率。施氮和接种AMF通过一定的交互作用对滨海盐土氮矿化过程产生影响。     

磷胁迫对不同基因型大豆苗期叶片特征的影响

通过砂培试验，对不同基因型大豆苗期的叶面积、叶绿素含量、叶厚度、栅栏组织厚度、海绵组织厚度进行了研究，结果表明：在缺磷和低磷胁迫下，各基因型的叶面积增大，磷低效基因型的叶绿素含量减少，而磷高、中效基因型却增大；叶片的各厚度指标在磷胁迫下并未表现出明确的变化趋势．此外，不同基因型对缺磷和低磷的反应程度存在显著差异，但磷高效基因型的叶面积、叶绿素含量的适应性均未表现出优势．     

A novel heteroseneous reaction for generating gaseous nitrous acid

The short-lived reactive specimen nitrous acid HONO was generated in the gas phase by the heterogeneous reaction of gaseous HCl with AgNO2 which can generate higher concentration of HONO than other methods. We investigated the process from generation to dissociation in the gas phase under different controlled temperatures, and discussed the ionization and reaction on the solid surface by combination of the photoelectron spectroscopy and photoionization mass spectroscopy （PES-PIMS） and in situ diffuse reflectance infrared Fourier transform spectroscopy （DRIFTS）.     

Combining docking and comparative molecular similarity indices analysis （COMSIA） to predict estrogen activity and probe molecular mechanisms of estrogen activity for estrogen compounds

Estrogen compounds are suspected of disrupting endocrine functions by mimicking natural hormones, and such compounds may pose a serious threat to the health of humans and wildlife. Close attention has been paid to the prediction and molecular mechanisms of estrogen activity for estrogen com- pounds. In this article, estrogen receptor a subtype （ERa） -based comparative molecular similarity indices analysis （COMSIA） was performed on 44 estrogen compounds with structural diversity to find out the structural relationship with the activity and to predict the activity. The model with the significant correlation and the best predictive power （R^2= 0.965, Q^2 LOO： 0.599, R^2 pred ： 0.825） was achieved. The COMSIA and docking results revealed the structural features for estrogen activity and key amino acid residues in binding pocket, and provided an insight into the interaction between the ligands and these amino acid residues.     

Diversity and high nitrogenase activity of endophytic diazotrophs isolated from Oryza rufipogon Griff.

Diversity and nitrogenase activity of endophytic diazotrophs colonized in the wild rice Oryza rufipogon Griff grown in Boluo, Huilai County in Guangdong Province and Lingshui County in Hainan Province were studied. Thirty-seven isolates obtained from Oryza rufipogon were identified as putative endophytic nitrogen-fixing bacteria by ARA （acetylene reduction assay） test and further confirmed by PCR amplification of nifH gene fragments. All obtained strains have ARA activity and the same sized nifH gene fragments. Above the similarity level of 80%, the obtained isolates were assigned as Group Ⅰ to Ⅷ by the clustering of IS-PCR fingerprints. The SDS-PAGE whole-cell protein patterns were similar to those of IS-PCR fingerprints. Components and contents of fatty acid methyl esters （FAMEs） were used to differentiate the representative strains （Ls13, Ls8, BL1, BL12, HL6, Ls4） from Group Ⅰ to Group Ⅵ. The six representative strains showed significant difference in contents and components of cellular fatty acid methyl ester. 16S rDNA sequencing analysis showed that strains of Group Ⅰ to Ⅶ were located in Enterobacteraceae （y-proteobacteria）. Strains of Group Ⅰ and Group Ⅱ were closely related to Klebsiella sp.; Strain Ls8 of Group Ⅱ was a little far away from the genus of Pantoea （homology level 96% with Pantoea agglomerans）, which may represent a new species or genus in Enterobacteraceae; Strains of Groups Ⅳ and Ⅴ belonged to different Enterobacter sp.; Strain Ls4 and Ls 9 representing Group Ⅵ were close to Citrobacter amalonaticus with 98% sequence similarity; Strain Ls15 of Group Ⅶ showed 98% sequence identity with Pantoea sp.; Strains of Group Ⅷ were assigned to the genus Ideonella （β-proteobacteria）. Based on the above results, endophytic diazotrophs isolated from O. rufipogon showed great diversity and some diazotrophs showed high nitrogenase activity with 42.52 μmol/mL. h C2H4. Inoculation to rice tests indicated that the isolated endophytic diazotrophs significantly promoted the rice growth.     

Effects of acetylene at low concentrations on nitrification, mineralization and microbial biomass nitrogen concentrations in forest soils

Temperate forest surface soils at the varying distances from main trunks (e.g., Pinus koraiensis and Quercus mongolica) were used to study the effects of acetylene (C₂H₂) at low concentrations on nitrification, mineralization and microbial biomass N concentrations of the soils, and to assess the contribution of heterotrophic nitrification to nitrous oxide (N₂O) emissions from soils. The use of acetylene at partial pressures within a range from 10 to 100 Pa C₂H₂ in headspace gas gave a significant decrease in N₂O emission at soil moisture of c. 45% water-filled porosity space, and the decrease was almost the same in each soil after exposure of C₂H₂ at low concentrations. Heterotrophic nitrification could account for 21%―48% of total N₂O emission from each soil; the contribution would increase with increasing distances from the Pinus koraiensis trunks rather than from the Quercus mongolica trunks. Under the experimental conditions, the use of C₂H₂ at low concentrations showed no significant influence on soil microbial biomass N, net N mineralization and microbial respiration. However, 100 Pa C₂H₂ in headspace gas could reduce carbon dioxide (CO₂) emissions from soils. According to the rapid consumption of 10 Pa C₂H₂ by forest soils and convenience for laboratory incubations, 50 Pa C₂H₂ in headspace gas can be used to study the origin of N₂O emissions from forest soils under aerobic conditions and the key associated driving mechanisms. The N₂O and CO₂ emissions from the soils at the same distances from the Quercus mongolica trunks were larger than those from the Pinus koraiensis trunks, and both emissions decreased as the distances from trunks increased. The stepwise regression analysis showed that 95% of the variability in soil CO₂ emissions could be accounted for by the concentrations of soil total C and water soluble organic C and soil pH, and that 72% of the variability in soil N₂O emissions could be accounted for by the concentrations of soil total N, exchangeable NH⁺₄-N and microbial biomass N and 25% of the variability in heterotrophic nitrification by the soil microbial biomass N concentration. The emissions of N₂O and CO₂ from forest soils after exposure of C₂H₂ at low concentrations were positively related to the net nitrification of the soils.     

贵州省豆科结瘤固氮植物资源调查

通过对贵州省豆科植物结瘤固氮资源的调查,共采集根瘤标本242份,分属豆科植物42属103种及变种,其中蝶形花亚科、含羞草亚科、云实亚科植物的结瘤率分别为95%,75%和5%;采集的根瘤中,96%生于寄主的侧根,形状以球形、长柱形为主,颜色多为白色、褐色.对分离纯化的55株根瘤菌进行了回接试验,回接结瘤率为33%.生态条件是影响根瘤的大小、数量以及有效性的原因之一.     

Effects of ultraviolet radiation B （UV-B） on photosynthesis of natural phytoplankton assemblages in a marine bay in Southern China

Solar ultraviolet radiation B (UVB) is known to have inhibitive effects on phytoplankton photosynthesis. UVB light decreases rapidly with increasing depth in the water column and exerts different degrees of UVB inhibitive effects on phytoplankton photosynthesis. In this study, the objectives were to quantify effects of UVB on phytoplankton photosynthesis and quantum yield, and to examine UVB effects on phytoplankton photosynthesis when light varies. The insitu experiments were conducted in Da Ya Bay, which is a semienclosed area in the subtropical South China. The results showed a significant reduction of photosynthetic rates and quantum yield in the presence of UVB. Maximum photosynthetic rates (Pmax) and maximum quantum yield (Φmax) were 11%-22% and 17%-49% less under solar radiation with UVB than without UVB. A simplified model was developed to describe the UVB biologically effective fluence rate (E*inh) as an exponential decay function of depth. Light-shift experiments, in which water samples from the surface and at depth of 4 m were divided into several subsamples, and each subsamples were then incubated at different depths with and without UVB in the water column, showed that phytoplankton from the deeper water (4 m) had more inhibitive rates by UVB than that from the surface when exposed to the same light condition.     

低磷和干旱胁迫条件下接种摩西球囊霉对白花草木犀营养吸收和生长的影响

 利用盆栽试验研究了低磷和干旱胁迫条件下接种摩西球囊霉(Glomus mosseae)对白花草木犀营养吸收和生长的影响.设置土壤相对含水量65%和35%两个处理,并设置磷营养0、25、50mg·kg^-13个水平(P₀,P₂₅,P₅₀),在上述两个因素的基础上分别进行接种和不接种摩西球囊霉处理.结果表明,干旱胁迫对白花草木犀根系菌根侵染率的影响不明显,但高磷水平(50mg·kg^-1)和干旱胁迫显著抑制了白花草木犀根系AM真菌的侵染(P<0.01).接种AM真菌不仅能够显著促进白花草木犀对N、P营养元素的吸收,还能够减弱干旱逆境对白花草木犀生长的影响.此外,无论是正常供水或者是干旱胁迫,接种AM真菌均显著增加了白花草木犀水分利用效率.在室内温室条件下,初步发现接种菌根能够促进干旱区、半干旱区牧草生长,恢复退化草原.     

Preparation of nano-compounded polyolefin materials through in situ polymerization technique: status quo and future prospects

Nano-compounding of polyolefins, an economical yet very effective route to high-performance polyolefin materials, has received considerable attention in recent years. Unlike most of the other polymers, polyolefins are chemically inert, which dictates that nano-compounding of polyolefins has to be conducted via in situ polymerization. In this review, a technological progress of the nano-compounding of polyolefins via in situ polymerization technique was summarized thoroughly, with emphasis laid on the current research status of polyolefin/montmorillonite (MMT) nanocomposites. A clear perspective for future researches on this specific family of materials was envisaged. Supported by National Natural Science Foundation of China (Grant No. 50373048) and State Key Development Program of Basic Research Program of Ministry of Science and Technology of China (Grant No. G2003CB615600)     

Environmental changes reflected by n-alkanes of lake core in Nam Co on the Tibetan Plateau since 8.4 kaB.P.

The n-alkanes are extracted from NMLC-1 core that was drilled in the Nam Co, central Tibet. They are measured by using Gas Chromatography and Mass Spectrometry （GC/MS） for componential and quantitative analyses. According to the constructed depth-age model, the component and concentration of n-alkanes, together with total organic carbon （TOC）, total nitrogen （TN） and carbonate are used to elucidate palaeoenvironmental changes of Nam Co during the past 8.4 ka. The results indicate that Holocene environment performs three stages in the lake area. In the stage of 8.4-6.7 kaB.P., it was warmer while precipitation slightly increased. This stage was ended by an obvious cold/dry event. During 6.7-5.8 kaB.P., temperature increased rapidly and reached its maximum values at about 6.0 kaB.P. The environments were warm/wet optimum for the blooming of terrestrial plants and submerged aquatic plants. After that, temperature decreased continuously and showed the lowest values at about 3.0 kaB.P. From 2.9 kaB.P, to the present, temperature rose again but alternated with cold and warm. The lake area tended to be dry after 1.4 kaB.P. During 600-400 aB.P., the environmental feature was the reflection of ＂Little Ice Age＂.