Potentilla jiaozishanensis sp. nov. (sect. Leptostylae,Rosaceae) from southwest China

Potentilla jiaozishanensis, a distinct new species of Rosaceae from Yunnan, China, is described and illustrated. Morphologically, it is closely related to P. stenophylla var. stenophylla but clearly differs from the latter by its bidentate leaflets, lanceolate epicalyx‐segments that are longer than the sepals, villose ovaries and achenes. Moreover, the pollen grains of P. jiaozishanensis are markedly different from those of P. stenophylla var. stenophylla in size and shape. The newly described species is endemic to the Jiaozishan Mountains, southwest China.     

Molecular Determinants of Hepatitis B and D Virus Entry Restriction in Mouse Sodium Taurocholate Cotransporting Polypeptide

Human hepatitis B virus (HBV) and its satellite virus, hepatitis D virus (HDV), primarily infect humans, chimpanzees, or tree shrews (Tupaia belangeri). Viral infections in other species are known to be mainly restricted at the entry level since viral replication can be achieved in the cells by transfection of the viral genome. Sodium taurocholate cotransporting polypeptide (NTCP) is a functional receptor for HBV and HDV, and amino acids 157 to 165 of NTCP are critical for viral entry and likely limit viral infection of macaques. However, the molecular determinants for viral entry restriction in mouse NTCP (mNTCP) remain unclear. In this study, mNTCP was found to be unable to support either HBV or HDV infection, although it can bind to pre-S1 of HBV L protein and is functional in transporting substrate taurocholate; comprehensive swapping and point mutations of human NTCP (hNTCP) and mNTCP revealed molecular determinants restricting mNTCP for viral entry of HBV and HDV. Remarkably, when mNTCP residues 84 to 87 were substituted by human counterparts, mNTCP can effectively support viral infections. In addition, a number of cell lines, regardless of their species or tissue origin, supported HDV infection when transfected with hNTCP or mNTCP with residues 84 to 87 replaced by human counterparts, highlighting the central role of NTCP for viral infections mediated by HBV envelope proteins. These studies advance our understanding of NTCP-mediated viral entry of HBV and HDV and have important implications for developing the mouse model for their infections.     

Niche Partition of Bacteriovorax Operational Taxonomic Units Along Salinity and Temporal Gradients in the Chesapeake Bay Reveals Distinct Estuarine Strains

The predatory Bacteriovorax are Gram-negative bacteria ubiquitous in saltwater systems that prey upon other Gram-negative bacteria in a similar manner to the related genus Bdellovibrio. Among the phylogenetically defined clusters of Bacteriovorax, cluster V has only been isolated from estuaries suggesting that it may be a distinct estuarine phylotype. To assess this hypothesis, the spatial and temporal distribution of cluster V and other Bacteriovorax phylogenetic assemblages along the salinity gradient of Chesapeake Bay were determined. Cluster V was expected to be found in significantly greater numbers in low to moderate salinity waters compared to high salinity areas. The analyses of water and sediment samples from sites in the bay revealed cluster V to be present at the lower salinity and not high salinity sites, consistent with it being an estuarine phylotype. Cluster IV had a similar distribution pattern and may also be specifically adapted to estuaries. While the distribution of clusters V and IV were similar for salinity, they were distinct on temperature gradients, being found in cooler and in warmer temperatures, respectively. The differentiation of phylotype populations along the salinity and temporal gradients in Chesapeake Bay revealed distinct niches inhabited by different phylotypes of Bacteriovorax and unique estuarine phylotypes.     

Different utilizable substrates have different effects on cometabolic fate of imidacloprid in Stenotrophomonas maltophilia

Imidacloprid, the largest selling insecticide in the world, is more stable in soil, and its environmental residue and effects are attracting people's close attention. One of imidacloprid metabolism pathways was degraded to CO₂ through olefin imidacloprid pathway. Here, we report that sucrose as a utilizable substrate enhanced the cometabolism of imidacloprid by Stenotrophomonas maltophilia CGMCC 1.1788 to produce 5-hydroxy imidacloprid, whereas when succinate was used as a utilizable substrate, 5-hydroxy imidacloprid from imidacloprid was transformed to olefin imidacloprid, and the latter was further degraded. The hydroxylation of imidacloprid required NAD(P)H, whereas the dehydration of 5-hydroxy imidacloprid to form olefin imidacloprid required succinate rather than NAD(P)H. NADPH greatly favored the hydroxylation of imidacloprid more than NADH, and NADPH inhibited the dehydration of 5-hydroxy imidacloprid to olefin imidacloprid, but NADH did not. Therefore, sucrose may be metabolized through hexose monophosphate pathway to produce mainly NADPH which participated in the hydroxylation of imidacloprid to 5-hydroxy imidacloprid and meanwhile inhibited the dehydration of 5-hydroxy imidacloprid to olefin imidacloprid, whereas succinate may be metabolized mainly through the tricarboxylic acid cycle to produce NADH which was involved in hydroxylation of imidacloprid to 5-hydroxy imidacloprid but did not inhibit the dehydration of 5-hydroxy imidacloprid to olefin imidacloprid. Our results have a significant meaning in further understanding the influence of different utilizable substrates on the cometabolic pathways and the fate of environmental imidacloprid.     

Resection Activity of the Sgs1 Helicase Alters the Affinity of DNA Ends for Homologous Recombination Proteins in Saccharomyces cerevisiae

The RecQ helicase family is critical during DNA damage repair, and mutations in these proteins are associated with Bloom, Werner, or Rothmund-Thompson syndromes in humans, leading to cancer predisposition and/or premature aging. In the budding yeast Saccharomyces cerevisiae, mutations in the RecQ homolog, SGS1, phenocopy many of the defects observed in the human syndromes. One challenge to studying RecQ helicases is that their disruption leads to a pleiotropic phenotype. Using yeast, we show that the separation-of-function allele of SGS1, sgs1-D664Δ, has impaired activity at DNA ends, resulting in a resection processivity defect. Compromising Sgs1 resection function in the absence of the Sae2 nuclease causes slow growth, which is alleviated by making the DNA ends accessible to Exo1 nuclease. Furthermore, fluorescent microscopy studies reveal that, when Sgs1 resection activity is compromised in sae2Δ cells, Mre11 repair foci persist. We suggest a model where the role of Sgs1 in end resection along with Sae2 is important for removing Mre11 from DNA ends during repair.     

Discovery of disubstituted piperidines and homopiperidines as potent dual NK1 receptor antagonists–serotonin reuptake transporter inhibitors for the treatment of depression

This report describes the synthesis, structure–activity relationships and activity of piperidine, homopiperidine, and azocane derivatives combining NK₁ receptor (NK₁R) antagonism and serotonin reuptake transporter (SERT) inhibition. Our studies culminated in the discovery of piperidine 2 and homopiperidine 8 as potent dual NK₁R antagonists-SERT inhibitors. Compound 2 demonstrated significant activity in the gerbil forced swimming test, suggesting that dual NK₁R antagonists-SERT inhibitors may be useful in treating depression disorders.     

应用纤维素结合域标签构建谷氨酸棒状杆菌表达系统

为优化谷氨酸棒状杆菌表达系统的纯化工艺,合成里氏木霉的CBD基因,将其与谷氨酸棒状杆菌分泌表达载体pXMJ19-sp连接,构建以CBD为纯化标签的重组载体pXMJ 19-sp-CBD.在该载体中插入GFP基因并转化至谷氨酸棒状杆菌,可获得分泌表达融合蛋白GFP-CBD的重组菌.该菌经IPTG诱导后的发酵液在紫外灯下显示强烈的绿色荧光,重组蛋白的分泌表达量达200 mg/L.利用CBD标签对纤维素柱的可逆性吸附,可直接对谷氨酸棒状杆菌分泌到培养基中的重组蛋白进行纯化,从而简化工艺和降低成本,为工业化大生产奠定基础.     

涪陵茎瘤芥种植区土壤肥力与产量的关系

采用田间调查研究和室内化学分析方法,研究了涪陵区主要茎瘤芥种植区土壤肥力因子及其与茎瘤芥产量的关系.结果表明: 茎瘤芥种植区土壤有效钙、镁、铁、锰、铜和锌含量较丰富,分别为3034、260、11.2、26.1、1.15和1.50 mg·kg^-1,有效磷适中,为19.3 mg·kg^-1;但有机质、碱解氮、速效钾和有效硫含量较为缺乏,分别为9.05 g·kg^-1、89.2 mg·kg^-1、106 mg·kg^-1和27.0 mg·kg^-1.茎瘤芥产量与土壤pH、有效钙呈极显著正相关,而与有效铁呈极显著负相关关系.土壤肥力因子对茎瘤芥产量的影响为：有效锰>有效铜>pH>有效铁>速效钾>有效钙>有效镁>有效硫>碱解氮>有效锌>有机质>有效磷;通过逐步回归分析剔除不显著变量,建立了土壤有效钙与茎瘤芥产量间的线性方程:Y=31636+3.63X₆.
     

中药渣蚓粪对玉米生长及土壤肥力特性的影响

采用盆栽试验,研究了中药渣蚓粪对玉米生长及土壤肥力的影响.结果表明: 随着蚓粪施用量的增加,玉米的株高、茎粗、叶面积、叶绿素含量均显著增加;生长60 d收获时,多数蚓粪处理的土壤容重显著降低;蚓粪处理的土壤pH显著高于对照和相应的化肥处理.蚓粪处理的土壤全氮、有机质含量也明显高于化肥处理,且随蚓粪施用量的增加,效果越趋显著.中药渣蚓粪可作为一种高效有机肥,其合理施用有助于改善土壤物理结构,缓解土壤的酸化进程,提高土壤有机质和氮素含量,有效促进作物生长.