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。     

鳗鱼肌肉的氨基酸及营养价值

通过对优质食用鱼类—鳗鱼肌肉的氨基酸进行测定证实,鳗鱼较之其它鱼类是一种营养价值更高、滋味更鲜美的鱼类。并且,根据结果氨基酸组成比例,可为鳗鱼的人工饲养等方面的研究提供理论依据。     

植酸钠对黑曲霉柠檬酸发酵产酸的促进效应

研究了植酸钠对黑曲霉柠檬酸发酵产酸的促进效应。在葡萄糖全合成培养基中添加１％的植酸钠,可使产酸比对照提高２．４倍;在薯粉、玉米粉等天然培养基中添加１％植酸钠,柠檬酸产量分别提高１．７倍和１．３倍。酶活性测定分析表明,植酸钠对柠檬酸代谢途径中的几种关键酶的活性有影响。     

A gene at 59 minutes on the Escherichia coli chromosome encodes a lipoprotein with unusual amino acid repeat sequences.

We report a 1.432-kb DNA sequence at 59 min on the Escherichia coli chromosome that connects the published sequences of the pcm gene for the isoaspartyl protein methyltransferase and that of the katF or rpoS (katF/rpoS) gene for a sigma factor involved in stationary-phase gene expression. Analysis of the DNA sequence reveals an open reading frame potentially encoding a polypeptide of 379 amino acids. The polypeptide sequence includes a consensus bacterial lipidation sequence present at residues 23 to 26 (Leu-Ala-Gly-Cys), four octapeptide proline- and glutamine-rich repeats of consensus sequence QQPQIQPV, and four heptapeptide threonine- and serine-rich repeats of consensus sequence PTA(S,T)TTE. The deduced amino acid sequence, especially in the C-terminal region, is similar to that of the Haemophilus somnus LppB lipoprotein outer membrane antigen (40% overall sequence identity; 77% identity in last 95 residues). The LppB lipoprotein binds Congo red dye and has been proposed to be a virulence determinant in H. somnus. Utilizing a plasmid construct with the E. coli gene under the control of a phage T7 promoter, we demonstrate the lipidation of this gene product by the incorporation of [3H]palmitic acid into a 42-kDa polypeptide. We also show that treatment of E. coli cells with globomycin, an inhibitor of the lipoprotein signal peptidase, results in the accumulation of a 46-kDa precursor. We thus designate the protein NlpD (new lipoprotein D). E. coli cells overexpressing NlpD bind Congo red dye, suggesting a common function with the H. somnus LppB protein. Disruption of the chromosomal E. coli nlpD gene by insertional mutagenesis results in decreased stationary-phase survival after 7 days.     

DcrA, a c-type heme-containing methyl-accepting protein from Desulfovibrio vulgaris Hildenborough, senses the oxygen concentration or redox potential of the environment.

The amino acid sequence of DcrA from Desulfovibrio vulgaris Hildenborough, a strictly anaerobic, sulfate-reducing bacterium, indicated homology with the methyl-accepting chemotaxis proteins from enteric bacteria (A. Dolla, R. Fu, M. J. Brumlik, and G. Voordouw, J. Bacteriol. 174:1726-1733, 1992). The homology is restricted to the cytoplasmic C-terminal signaling domain. The periplasmic N-terminal sensor domain was found to contain a unique sequence, CHHCH, corresponding to a consensus c-type heme binding site. A pretreated, DcrA-specific polyclonal antiserum, generated against DcrA protein overproduced in Escherichia coli, was used for immunoprecipitation of 35S-labeled DcrA from D. vulgaris and Desulfovibrio desulfuricans G200(pJRFR2), a transconjugant that overexpresses functional DcrA. Labeling of the latter with the heme precursor 5-amino-[4-14C]levulinic acid, followed by immunoprecipitation, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and fluorography, confirmed the presence of c-type heme, while labeling with L-[methyl-3H]methionine in the absence of protein synthesis confirmed that DcrA is a methyl-accepting protein. The base liability of the incorporated radioactivity indicated methyl ester formation like that occurring in the methyl-accepting chemotaxis proteins of enteric bacteria. L-[methyl-3H]methionine labeling of D. desulfuricans G200(pJRFR2) under different conditions indicated that methyl labeling of DcrA decreased upon addition of oxygen and increased upon subsequent addition of the reducing agent dithionite. These results indicate that DcrA may serve as a sensor of oxygen concentration and/or redox potential.     

Map locations of mouse hepatitis virus temperature-sensitive mutants: confirmation of variable rates of recombination.

Using standard genetic recombination techniques, studies in our laboratory suggest that recombination rates are very high and vary in different portions of the mouse hepatitis virus (MHV) genome. To determine the actual recombination frequencies in the MHV genome and localize the nucleotide boundaries of individual viral genes, we have sequenced temperature-sensitive and revertant viruses to identify the location of specific mutant alleles. Complementation group F RNA+ ts mutants (LA7, NC6, and NC16) each contained a unique mutation which was tightly linked to the ts phenotype and resulted in a conservative or nonconservative amino acid change in the MHV S glycoprotein gene. In agreement with previous recombination mapping studies, the mutation in LA7 and NC6 mapped within the S1 domain while NC16 mapped within the S2 domain. To determine the map coordinates of the MHV polymerase genes, several RNA- mutants and their revertants belonging to complementation groups C (NC3 and LA9) and E (LA18 and NC4) were also sequenced. Mutations were identified in each virus that were tightly linked to the ts phenotype and resulted in either a conservative or nonconservative amino acid change. The group C allele spanned the ORF 1a/ORF 1b junction, while the group E mutants mapped at the C terminus of ORF 1b about 20 to 22 kb from the 5' end of the genome. Mutation rates, calculated from the reversion frequencies of plaque-purified ts viruses requiring a single nucleotide alteration for reversion, approached 1.32 (+/- 0.89) x 10(-4) substitutions per nucleotide site per round of template copying. Detailed recombination mapping studies across known distances between these different ts alleles has confirmed that homologous recombination rates approached 25% and varied within different portions of the MHV genome.     

银杏授粉研究初报

本文报道银杏授粉的适宜品种,气候条件、不同时期、方法、浓度、雌花不同发育阶段等试验结果．为提高银杏的座果率提供有效的技术措施。     

银杏扦插繁殖试验

本文报道银杏扦插繁殖技术。采用不同插穗、机械处理、不同激素及浓度处理进行扦插繁殖试验．扦插成活率可达９０—１００％。