生物复苏——大绝灭后生物演化历史的第一幕

生命史是一部生物界短期,快速剧变与长期,慢速稳定相互交替的历史。大绝灭（即集群绝灭）事件反映了全球环境的大突变,点断了地质历史中的生命记录及其发展历程,预示着生物界的演化出现了最有意义的飞跃,近年来尝试研究大绝灭后全球生物界的残存－复苏及其基本型式,并探索复苏的控制因素,标志着地质科学中一个重心的转移（即从大绝灭转向其后的生物残存与复苏的研究）。生物复苏揭示了大绝灭后生物演化历史的第一幕,其研究的     

苏云金芽孢杆菌δ-内毒素基因穿梭质粒的构建

在农业生产中长期使用化学农药已对环境和生态平衡造成一定破坏作用,同时有不少害虫也逐渐产生抗药性从而引起某些害虫的大流行,给农业生产带来巨大损失。应用苏云金杆菌杀虫蛋白基因(Bt基因)可构建具有抗虫作用的抗虫工程菌,这样通过拌种或植物叶面喷雾可达到快速、经济、有效的防治虫害的目的。国际上抗虫工程菌研究应用很快,如美国将BI基因转入到一种正常情况下定居在植物组织中的棒杆菌,将这种工程菌拌玉米种子,这样随植物生长该菌在植物体内大量繁殖,当玉米螟在茎和叶取食时,即因食用表达苏云金杆菌毒蛋白的工程菌而死亡。 田颖川等已克隆了苏云金芽孢杆菌内毒素基因CryIA(b)和CryIA(c)。本文将Bt基因CryIA(c)插入到大肠-枯草穿梭载体pBE-2中构建成Bt毒蛋白基因穿梭质粒pAMY,利用电穿孔法转人大肠杆菌DH5a,枯草芽孢杆菌B.subtilis BR151,IA511,野生型蜡状芽孢杆菌B.cereusa-47,短芽孢杆菌B.brevis A-5和枯草芽孢杆菌90-8,获得了具有较高杀虫活性的工程菌克隆。     

A single tryptophan on M2 of glutamate receptor channels confers high permeability to divalent cations.

Ionotropic glutamate receptors (iGluRs) of the alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate/kainate subtype display lower permeability to Ca2+ than the N-methyl-D-aspartate (NMDA) subtype. The well-documented N/Q/R site on the M2 transmembrane segment (M2) is an important determinant of the distinct Ca2+ permeability exhibited by members of the non-NMDA receptor subfamily. This site, however, does not completely account for the different permeation properties displayed by non-NMDA and NMDA receptors, suggesting the involvement of other molecular determinants. We have identified additional molecular elements on M2 of the alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate/kainate receptor GluR1 that specify its permeation properties. Higher permeability to divalent over monovalent cations is conferred on GluR1 by a tryptophan at position 577, whereas blockade by external divalent cations is imparted by an asparagine at position 582. Hence, the permeation properties of ionotropic glutamate receptors appear to be primarily specified by two distinct determinants on M2, the well-known N/Q/R site and the newly identified L/W site. These findings substantiate the notion that M2 is a structural component of the pore lining.     

Evidence for ion chain mechanism of the nonlinear charge transport of hydrophobic ions across lipid bilayers.

The conductivity across a lipid bilayer by tetraphenylborate anion is increased 10-fold on the photoformation of lipophilic porphyrin cations. The cations alone have negligible conductivity. This nonlinear photogenerated increase of ion conductivity is termed the photogating effect. Substitution of H by Cl in the para position of tetraphenylborate leads to a 100-fold enhancement of conductivity, whereas the dark conductivities for this and other substituted borates are the same. Moreover, the halo-substituted borates show a large enhancement of conductivity in the low concentration range (10(-8) M), whereas that of tetraphenylborate is small and space charge is negligible. The enhanced ion conductivity has great structural sensitivity to the structure of the anion, the cation, and the lipid, whereas the partition coefficient of all the borates and the concentration of photoformed cations are only slightly affected. The photogated ion transport has a twofold larger activation energy than transport in the dark. Time-resolved photocurrents and voltages demonstrate that the translocation rate of the porphyrin cation is also enhanced 100-fold by the Cl-borate anion but only 10-fold by the H-borate anion. For these reasons the nonlinear gating effect cannot be explained by electrostatics alone, but requires an ion chain or ion aggregate mechanism. Kinetic modeling of the photoinduced current with a mixed cation-anion ion chain can fit the data well. The photogating effect allows the direct study of ion interactions within the bilayer.     

利用激光微束穿刺法将外源基因导入小麦的研究

用激光微束穿刺法将携带有新霉素磷酸转移酶（ＮＰＴ－Ⅱ）基因的质粒ｐＪＩＴ１０１导入京花１号小麦幼胚细胞。方法是将小麦幼胚细胞进行高渗缓冲液预处理,用微米级的激光微束处理,然后在卡那霉素培养基上筛选出具抗性的愈伤组织及绿色小植株。第一年,从１５０个小麦幼胚中,在卡那霉素培养基上筛选出４株绿苗,取两株进行ＮＰＴ－Ⅱ酶活性分析,测到了ＮＰＴ－Ⅱ酶的活性。第二年重复实验,从２４５个小麦幼胚中,经筛选获得１株绿苗,进行了叶片ＤＮＡＰＣＲ扩增检测,转化的绿色小苗扩增出所导入的ＮＰＴ－Ⅱ基因编码的片段。结果表明,外源ＮＰＴ－Ⅱ基因已导入了小麦,并实现了整合表达。     

PREDICTING HETEROSIS IN GRAIN YIELD FROM GENETIC DIVERGENCE ANALYSIS IN SUNFLOWER

Geneticdivergenceanalysiswasconductedbasedonperformanceof12quantitativetraitsin85sunflowerinbredlines,tostudyitseffectivenessinpredictingyieldheterosisofthe72hybridsfromthem.Resultsshowedthatlinearregressionmodelfittherelationshipbetweenheterosisofseedoilcontentandgeneticdistance,andquadraticregressionequationtherelationshipbetweengrainyieldheterosisandgeneticdistance,whichcanbeusedinpredictingheterosisfromtheparentperformances.Clusteranalysiswaseffectivetocertainextent,butitsutilizationshouldbelimited.Grainyieldandoilcontentcanbeimprovedsimutaneouslyaccordingtotherelationsbetweengeneticdivergenceandtheheterosisofthesetwotraits.     

锈寄生菌对落叶松褐锈病的抑制效应

目测及镜检结果表明,褐锈菌被锈寄生菌寄生后,夏孢子堆由桔红渐变为灰褐,后期夏孢子失去发芽力,孢子堆原基处只存有寄生菌的分生孢子器．锈寄生菌的发酵液代谢产物含有３种抗性物质．自７月中下旬至９月中旬,分生孢子的发生量多于褐锈菌的孢子量,表明落叶松褐锈病的发生程度随着锈寄生菌寄生率的增加而减轻．     

地膜条件下土壤生态因子与玉米产量的关系

研究干旱地区地膜条件下,土壤生态因子对玉米产量的影响．结果表明,最佳种植模式为作物距地膜中心线２１．３—３３．２Ｃｍ,施纯Ｎ＋Ｐ为５９８—７４３ｋｇ·ｈａ－１,玉米产量为１４４９２≤Ｙ佳≤１６５９ｋｇ·ｈ－１．该种植模式有利于提高作物产量及残膜回收．