农业化学投入强度替代效率及其影响因素

采用SE-DEA和空间基尼系数,研究了2000—2016年我国农业化学投入强度替代效率,并运用Tobit模型分析了我国及各地区替代效率的驱动因素.结果表明: 我国农业化学投入强度替代的综合效率和规模效率呈现出“N”字型趋势,纯技术效率则波动上升,替代效率的地区差异明显,东部地区更倚重替代要素的投入规模;各年份全国省域差异最高的是综合效率,其次为纯技术效率,规模效率的区域差异性最小,地区内部省域差异逐渐减小,东部地区省域差异最大;农业化学投入替代效率受农业技术水平、农户收入水平、农业生产结构、农业发展程度和工业化水平的显著影响,各地区受各因素影响差异明显.推动农业化学投入替代效率,要从提高农业化学投入强度替代要素的投入效率、调整农用工业发展结构、关注农民收入水平和修订农业化学投入强度替代的补贴政策等方面入手.     

Contaminant Removal of Domestic Wastewater by Constructed Wetlands： Effects of Plant Species

A comparative study of the efficiency of contaminant removal between five emergent plant species and between vegetated and unvegetated wetlands was conducted in small-scale （2.0 m×1.0 m×0.7 m, lengthxwidthxdepth） constructed wetlands for domestic wastewater treatment in order to evaluate the decontaminated effects of different wetland plants. There was generally a significant difference in the removal of total nitrogen （TN） and total phosphorus （TP）, but no significant difference in the removal of organic matter between vegetated and unvegetated wetlands. Wetlands planted with Canna indica Linn., Pennisetum purpureum Schum., and Phragmites communis Trin. had generally higher removal rates for TN and TP than wetlands planted with other species. Plant growth and fine root （root diameter ≤ 3 mm） biomass were related to removal efficiency. Fine root biomass rather than the mass of the entire root system played an important role in wastewater treatment. Removal efficiency varied with season and plant growth. Wetlands vegetated by P. purpureum significantly outperformed wetlands with other plants in May and June, whereas wetlands vegetated by P. communis and C. indica demonstrated higher removal efficiency from August to December. These findings suggest that abundance of fine roots is an important factor to consider in selecting for highly effective wetland plants. It also suggested that a plant community consisting of multiple plant species with different seasonal growth patterns and root characteristics may be able to enhance wetland performance.     

Changes of 5＇ Terminal Nucleotides of PCR Primers Causing Variable T-A Cloning Efficiency

T-A cloning takes advantage of the unpaired adenosyl residue added to the 3＇ terminus of amplified DNAs by Taq and other thermostable DNA polymerase and uses a Ilnearlzed plasmld vector with a protruding 3＇ thymldylate residue at each of Its 3＇ termini to clone polymerase chain reaction （PCR）-derived DNA fragments. It Is a simple, reliable, and efficient Ilgatlon-dependent cloning method for PCR products, but the drawback of variable cloning efficiency occurs during application. In the present work, the relationship between variable T-A cloning efficiency and the different 5＇ end nucleotlde base of primers used In PCR amplification was studied. The results showed that different cloning efficiency was obtained with different primer pairs containing A, T, C and G at the 5＇ terminus respectively. The data shows that when the 5＇ end base of primer pair was adenosyl, more white colonies could be obtained In cloning the corresponding PCR product In comparison with other bases. And the least white colonies were formed when using the primer pair with 5＇ cytldylate end. The gluanylate end primers resulted In almost the same cloning efficiency In the white colonies amount as the thymldylate end primer did, and this efficiency was much lower than that of adenosyl end primers. This presumably is a consequence of variability In 3＇dA addition to PCR products mediated by Taq polymerase. Our results offer instructions for primer design for researchers who choose T-A cloning to clone PCR products.     

Comparison of transformation efficiency of piggyBac transposon among three different silkworm Bombyx mori Strains

The transformation rate of three different strains of silkworm Bombyx mori was comparedafter the introduction of enhanced green fluorescence protein (EGFP)-encoding genes into the silkwormeggs by microinjection of a mixture of piggyBac vector and helper plasmid containing a transposase-encodingsequence.Although there were no significant differences among the three strains in the percentages offertile moths in microinjected eggs (P=0.1258),the percentages of G_0 transformed moths in fertile mothsand injected eggs were both significantly different (P=0.01368 and P=0.02398, respectively).Thetransformation rate of the Nistari strain (Indian strain) was significantly higher than that of the other twostrains,Golden-yellow-cocoon (Vietnamese strain) and Jiaqiu (Chinese strain),which had similar rate. Theseresults indicate that the transformation efficiency of the piggyBac-based system might vary with silkwormstrains with different genetic backgrounds.The presence of endogenous piggyBac-like elements might bean important factor influencing the transformation efficiency of introduced piggyBac-derived vectors,andthe diverse amount and activation in different silkworm strains might account for the significant differences.     

植物硼营养研究的重要进展与展望

硼是高等植物必需的矿质营养元素, 但是人们对硼行使生理功能及其分子机理的认识远落后于其它必需营养元素。近几年国际上植物硼营养的研究取得了一些重要的突破。首先是进一步明确了B-RG-II复合物的形成及其影响细胞壁结构和功能的分子机制, 并且发现B-RG-II的形成及其含量与陆生植物的进化密切相关。其次是在拟南芥中克隆了第一个植物硼转运子基因 BOR1, 并揭示了它的作用机理; 通过转基因实验证明了植物硼的高效吸收与水通道基因NIP5;1密切相关。进而通过大量的种质筛选, 从油菜、小麦、大麦及棉花等农作物中获得一批硼高效吸收利用的优异种质材料, 并开展了硼高效QTL定位和克隆。本文详细综述了以上几个方面的研究进展, 并对进一步的研究做了展望。     

动物基因组编辑中提升CRISPR/Cas9介导的同源重组效率研究进展*

基因组编辑技术可以对DNA或RNA进行精准改造,极大地促进了生命科学的发展。CRISPR/Cas9系统在靶位点诱导DNA发生双链或单链损伤,细胞对损伤部位采用无供体模板的非同源末端连接(non-homologous end joining,NHEJ)或有供体模板的同源重组(homologous recombination,HR)修复。基于HR的基因组编辑策略通常被用于获得DNA的精准改造,而NHEJ在动物DNA损伤修复中起主导作用。为了提升HR效率,研究人员设计了多种方案,包括CRISPR/Cas9系统优化和DNA修复通路调控等。从DNA损伤修复途径、Cas9变体选择、sgRNA设计、供体模板设计、DNA修复途径相关蛋白功能调控、供体模板募集效率提升、细胞周期调控及编辑细胞生存效率提升等方面详细综述了相关研究成果,发现尚未开发出放之四海而皆准的HR提升策略,基于HR的基因组编辑需要针对具体案例制定个体化策略。旨在为动物基因组编辑中提升CRISPR/Cas9介导的HR效率研究提供理论参考,为动物基因功能分析、基因治疗和经济动物基因编辑育种提供帮助。     

丛枝菌根网络介导的植物间信号交流研究进展及展望

丛枝菌根(arbuscular mycorrhizal, AM)真菌是一类能够与绝大多数陆地植物形成共生关系的土壤真菌, 其根外菌丝可以侵染不同植物根系且可以进行菌丝融合, 从而形成丛枝菌根网络(arbuscular mycorrhizal networks, AMNs)。AMNs可以在植物之间转运水分及营养元素如碳(C)、氮(N)、磷(P)等, 最近研究表明AMNs还可以在植物遭受环境胁迫时向邻近植物传递防御信号, 对周围植物起到“预警”作用。目前, 关于环境胁迫条件下AMNs介导的信号物质传递研究仍处于起步阶段, 许多问题亟待回答。该文首先回顾了目前有关AMNs介导的信号物质传递研究进展, 继而梳理了这一研究领域值得进一步探究的科学问题, 包括AMNs在植物间传递防御信号的可能途径及相关机制, AMNs介导的信号传递对菌根共生体系的可能影响, 以及AMNs研究中常用的技术及其发展, 最后讨论了AMNs介导的信号物质传递在作物保护等方面的可能应用。     

刺激大鼠离断背根外周端对相邻背根电活动的影响

在切断大鼠左侧１２、１３背根后,观察电刺激（刺激参数为０．８－１．２ｍＡ,１００Ｈｚ,０．５ｍｓ,总时程２ｓ）Ｌ２背根外同对Ｌ３背根放电活动的影响。结果表明：连续多次刺激Ｌ２背根可使Ｌ３背根平均放电频率（ＭＤＦ）逐步增加,增加量与刺激次数中于明显直线正相关,各次刺激后的时程分析表明,这种增频作用具有明显的累积效应的后效应,并与刺激前１３背根的活动状态密切相关,刺激前放电活动较强者其增频作用更明显。     

吗啡对大鼠海马神经元突触传递的作用及机制探讨

目的 :从离子通道角度研究吗啡对中枢神经系统兴奋性及抑制性突触传递的作用并探讨其机制。方法 :　原代培养新生Wistar大鼠的海马神经元。采用膜片钳技术研究吗啡对其兴奋性及抑制性突触后电流及谷氨酸诱发电流的影响。结果 :①吗啡可明显增强海马神经元兴奋性突触传递 ,加吗啡后自发兴奋性突触后电流 (sEPSC)的发放频率增加了 ( 2 0 7.8± 2 0 .9) %。此作用可被阿片受体阻断剂纳洛酮阻断 (P <0 .0 1) ;②吗啡对微小兴奋性突触后电流 (mEPSC)的发放频率及谷氨酸诱发电流的幅度没有明显影响 (P >0 .0 5 ) ;③吗啡可明显抑制神经元自发抑制性突触后电流 (sIPSC) ,纳洛酮可拮抗吗啡作用 (n =13 ,P <0 .0 1)。结论 :实验结果提示吗啡对海马神经元的兴奋作用不是由于吗啡直接作用于兴奋性氨基酸—谷氨酸突触传递过程 ,而是可能由于抑制了抑制性中间神经元 ,间接产生的兴奋作用。