大刍草稀有等位基因促进玉米密植高产

密植是提高作物单位面积产量、促进粮食增产的重要途径之一。叶夹角是影响玉米(Zea mays)密植的关键因子。中国农业大学田丰课题组最近克隆了2个调控玉米叶夹角的数量性状位点(QTL)——UPA1和UPA2, 揭示了这2个位点的功能基因(brd1和ZmRAVL1)通过油菜素内酯(BR)信号通路调控叶夹角。UPA2位于ZmRAVL1上游9.5 kb, 可与DRL1蛋白结合。另一个影响玉米叶夹角的蛋白LG1可以激活ZmRAVL1的表达; DRL1蛋白与LG1蛋白直接互作抑制LG1对ZmRAVL1的激活表达。玉米祖先种大刍草(teosinte)的UPA2位点序列与DRL1蛋白结合能力更强, 导致大刍草ZmRAVL1的表达受到更强的抑制, 下调表达的ZmRAVL1进一步使下游基因brd1的表达下调, 进而降低叶环区的内源BR水平, 导致叶夹角变小。将大刍草的UPA2等位基因导入到玉米中或对玉米中ZmRAVL1进行基因编辑, 在密植条件下均可显著提高玉米产量。上述发现为高产玉米品种的分子育种改良提供了重要理论基础和基因资源。     

高效液相层析法纯化人胎盘谷胱甘肽硫转移酶

足月分娩的新鲜胎盘组织制成匀浆后,经高速离心、超速离心,谷胱甘肽(GSH)Sepharose 6B亲合层析,Amicon pM-10膜超过滤及高效液相层析,最终经SDS-PAGE鉴定,结果呈现单一亚基区带,其亚基分子量为25000。 根据我们现有高效液相设备条件,用ODS柱代替RadulovicL等报道的特异阴离子柱,用磷酸盐洗脱液代替含谷胱甘肽、二硫苏糖醇及氯化钾的梯度洗脱液,从人胎盘组织成功地制备了谷胱甘肽硫转移酶(GST)纯酶,全过程在15min内完成,保留时间及主峰面积的重复性均较理想,7次实验结果的变异系数为0.2％,最终纯化578.9倍。本研究为各种形式GST的纯化制备提供了一个新的、重复性好、分辨率高及回收理想的简易方法。     

Chemical modification of Bacillus thuringiensis subsp. thuringiensis (HD-524) trypsin-activated endotoxin: implication of tyrosine residues in lepidopteran cell lysis

A purified protein fraction from a solubilized and trypsin-digested extract of Bacillus thuringiensis subsp. thuringiensis (HD-524) fermentation powder was lytic to cells from several lepidopteran lines. Maximum yield was obtained by alkaline carbonate-thiocyanate solubilization of washed powder followed by trypsin digestion and Sephacryl (S-300) chromatography. The alkaline carbonate-solubilized fraction consisted predominantly of two bands on sodium dodecyl sulfate-polyacrylamide gel electrophoresis with MW of 144 +/- 0.9 kDa and 134 +/- 1.4 kDa. After trypsin treatment and column chromatography, the cytolytic fraction consisted of a major band with a MW of 60.0 +/- 1.8 kDa and a minor band of 69 +/- 0.9 kDa. Cells from Trichoplusia ni (TN368) were most susceptible to lysis with 50% of cells lysed at 3 micrograms/ml, followed by Spodoptera frugiperda cells (SF21AE) exhibiting 50% cell lysis at 5 micrograms/ml and Lymantria dispar cells (Ld652Y) showing 40% lysis at 10 micrograms/ml. Chemical modification of the polypeptides was performed to determine the role of certain amino acid residues in the cytolytic activity. The group-specific reagent tetranitromethane was used to nitrate and oxidize tyrosine and cysteine residues, respectively. Cysteine residues alone were also modified with p-hydroxymercuribenzoic acid. Lysine residues were modified with O-methylisourea. Of the three types of amino acid residues, only the modification of tyrosine resulted in reduced cell lysis.     

草鱼免疫应答的初步研究

研究了草鱼在不同水温条件下受抗原刺激后其中和抗体的变化。15℃培养条件下中和抗体上升缓慢,9周内滴度低于1:8;20℃时,3周后抗体可上升到1:256,最高达1:5270,而在25℃时,1周中和抗体即达到1:570,最高可达1:20000以上。并探索了从草鱼血清中提纯抗体的条件,研究其抗体的特性。草鱼血清中的抗体为大分子蛋白,容易解离为抗原性相同,分子量近似于人IgG的较小分子,含有较多的二硫键,具有类似IgM的某些特性。     

Flavonol glycoside production in callus cultures of Epimedium diphyllum.

Callus cultures of Epimedium diphyllum produced a large amount of epimedoside A in addition to a small amount of diphylloside B, ikarisoside C, epimedoside E, diglycosides of des-O-methylanhydroicaritin (8-gamma, gamma-dimethylallylkaempfero). Icariin, epimedins A-C, which are glycosides of anhydroicaritin, were also produced in the callus cultures. Contents of the flavonol glycosides in callus tissue were higher than those of mother plants, but the composition of each flavonol glycoside mixture in the callus cultures was different from that of the original plants. The time-course experiments showed that an inverse relationship existed between cell growth and flavonol glycoside production. Effects of hormonal factors on cell growth and flavonol glycoside production indicated that 2,4-dichlorophenoxyacetic acid was needed for the production of flavonol glycosides.     

Differentiation of extracutaneous melanocytes in embryos of the turtle, Trionyx sinensis japonicus.

The present study investigates the mode of differentiation of neural crest-derived melanocytes in the embryos of the soft-shell turtle, Trionyx sinensis japonicus. DOPA reaction-positive melanoblasts were first detected in 10-day-old embryos. Melanocyte differentiation in terms of pigmentation takes place from the day 16 of development. Melanin pigments were found in the dorsal integument as well as in various extracutaneous tissues such as skeletal muscle, dorsal aorta, peritoneum, blood vessels, choroid, lung, bone marrow, fat tissues and in the connective tissue of the nose. These results suggest the presence of a specific environmental regulation of the melanoblast differentiation in the soft-shell turtle.     

Ultrastructure of the micropyle and its relationship to pollen tube growth and synergid degeneration in sunflower

Summary Ultrastructural studies made on the micropyle of sunflower before and after pollination resulted in the following observations. (1) The micropyle is closed instead of a hole or canal. The inner epidermis of the integument on both sides of the micropyle is in close contact at the apex of the ovule. The boundary between the two sides consists of two layers of epidermal cuticle. (2) The micropyle contains a transmitting tissue. The micropyle is composed of an intercellular matrix produced by the epidermal cells of the integument. (3) The micropyle is asymmetrical, and is much wider on the side proximal to the funicle. On the funicle side the cells adjacent to the micropyle are similar to those of the transmitting tissue: they have large amounts of intercellular matrix and contain abundant dictyosomes, rough ER, and starch grains, and provide an appropriate environment for growth of the pollen tubes. The cells distal to the funicle are rich in rough ER and lipid bodies; they lack large intercellular spaces. (4) The micropyle is variable in the axial direction, i.e., it is much larger and more asymmetric at the level distal to the embryo sac than at a level close to the embryo sac. After pollination, one to four pollen tubes are seen in a micropyle. During their passage through the micropyle, most pollen tubes are restricted to the side proximal to the funicle. There is a greater tendency (81%) for the degenerate synergid to be located toward the funicle, i.e., at the same side as the pollen tube pathway. The data indicate a close relationship between micropyle organization, orientation of pollen tube growth, and synergid degeneration.     

进化距离与相对替代率的比较研究

系统树是描述物种、人种甚至基因间亲缘关系和演化的重要工具,必须以进化距离或(相对)替代率作为重要的参数。但以哪一个参数构建的树更能反映真实的系统树呢?事实上迄今并无人对此作过认真的研究。本文以模拟数据并用方差分析法检验两个参数的异同并讨论其包含的生物学意义。研究结果表明,当氨基酸的替代率和核苷酸的替代率分别为0.18和0.13时,它们的进化距离分别为0.199和0.143。经方差分析证实,若检验的氨基酸和核苷酸最大数目均为75只时,不论以替代率或进化距离中那一个作为构树参数,拓扑树事实上几乎只有一个。这就是说,该时拓扑树可靠性很大,而且随着它们替代率的减少,则检验的氨基酸和核苷酸的数目会随之增加。但是一旦氨基酸的替代率和核苷酸的替代率超过上述数字,则两个参数构建的树在拓扑长度上是不等价的。经分析,若进化距离大致上与进化时间成线性关系的话,则应选用进化距离。用进化距离重建的系统树事实上支持中性学说;若进化距离与进化时间显著地不存在线性关系的话,则可选用替代率,该情况表明中性学说不适用,似更倾向于新达尔文主义。     

Role of minor subunits in the structural asymmetry of the Escherichia coli F1-ATPase

The beta subunits of the Escherichia coli F1-ATPase react independently with chemical reagents (Stan-Lotter, H. and Bragg, P.D. (1986) Arch. Biochem. Biophys. 248, 116-120). Thus, one beta subunit is readily crosslinked to the epsilon subunit, another reacts with N-N'-dicyclohexylcarbodiimide (DCCD), and a third one is modified by 4-chloro-7-nitrobenzofurazan (NbfCl). This asymmetric behaviour is not due to the association of the delta and epsilon subunits of the ATPase molecule with specific beta subunits since it is maintained in a delta, epsilon-deficient form of the enzyme.     

Mechanism of adenylate kinase. Structural and functional demonstration of arginine-138 as a key catalytic residue that cannot be replaced by lysine

Replacement of the arginine-138 of adenylate kinase (AK) by lysine or methionine resulted in a decrease in kcat by a factor of 10(4), increases in Km by a factor of 10-20, and relatively little changes in dissociation constants. Proton nuclear magnetic resonance (NMR) studies were then undertaken to obtain structural information for quantitative interpretation of the kinetic data. Since the lysine mutant (R138K) represents a conservative mutation with surprisingly large effects on kinetics, structural studies were focused on the wild type (WT) and R138K. The results and conclusions are summarized as follows: (i) The aromatic spin systems of WT and R138K were assigned from total correlated spectroscopy (TOCSY). Comparison of the chemical shifts of aromatic protons, one-dimensional spectra, TOCSY, and nuclear Overhauser enhanced spectroscopy (NOESY) indicated that the conformation of R138K was almost unperturbed relative to that of WT. Thus Arg-138 is not important for the tertiary structure. (ii) Proton NMR titrations with AMP and MgATP suggested that substrate binding affinities and substrate-induced conformational changes are nearly identical between WT and R138K. Thus arginine-138 should not be involved in stabilizing the first substrate in the binary complex. (iii) Notable differences were observed between the proton NMR spectra of the WT and R138K complexes with the reaction mixture, which agrees with the perturbation in the Km values of R138K. The differences were analyzed in detail by using a "static reaction mixture'--p1, p5-bis(5'-adenosyl)pentaphosphate (MgAP5A). The aromatic spin systems of WT + MgAP5A and R138K + MgAP5A were partially assigned from various two-dimensional spectra.(ABSTRACT TRUNCATED AT 250 WORDS)