应用组织培养方法选育耐盐碱水稻新品种

本文报道了应用组织培养方法,选育耐盐碱水稻.作法是将去壳的水稻种子经常规消毒接种在脱分化培养基诱导形成愈伤组织,继代一次,转移到加压培养基(MS+2.4-D2mg/L+NaCl1%+NaHCO_30.5%),处理20天,再转移到分化培养基,分化并培育出组培水稻119份,简称为D水稻.D水稻又经过盐碱地的实际种植,大批D水稻被田间粗筛而淘汰掉,保存下20份从形态表现和耐盐碱性较好的材料.然后对20份D水稻的脯氨酸含量和叶绿素含量进行测定分析并与其耐盐碱性进行比较,把各项指标综合起来鉴定其耐盐碱性,最终筛选出7价为耐盐碱性较强的水稻新品系.其中647—4表现为最耐盐碱、抗病、高产的水稻.     

Characterization of the IS895 family of insertion sequences from the cyanobacterium Anabaena sp. strain PCC 7120.

A family of repetitive elements from the cyanobacterium Anabaena sp. strain PCC 7120 was identified through the proximity of one element to the psbAI gene. Four members of this seven-member family were isolated and shown to have structures characteristic of bacterial insertion sequences. Each element is approximately 1,200 bp in length, is delimited by a 30-bp inverted repeat, and contains two open reading frames in tandem on the same DNA strand. The four copies differ from each other by small insertions or deletions, some of which alter the open reading frames. By using a system designed to trap insertion elements, one of the elements, denoted IS895, was shown to be mobile. The target site was not duplicated upon insertion of the element. Two other filamentous cyanobacterial strains were also found to contain sequences homologous to IS895.     

Chemical synthesis and surface activity of lung surfactant phospholipid analogs. III. Chiral N-substituted ether-amide phosphonolipids

A homologous series of chiral (R) ether-amide phosphonolipid analogs of naturally occurring (R) glycerophospholipids were synthesized and characterized for their interfacial behaviors. The phosphonolipids possess isoteric ether, amide, and phosphonate functions at positions corresponding to the sn-1, sn-2, and sn-3 ester functions, respectively, of naturally occurring glycerophospholipids. All compounds were synthesized with disaturated C16:0 alkyl/acyl moieties to give structural analogy with dipalmitoyl phosphatidylcholine (DPPC), the major glycerophospholipid component of lung surfactant. Further substitutions at the headgroup nitrogen were also used to generate differences in headgroup size and polarity in the synthetic compounds. The surface activity of the ether-amide phospholipids was investigated in terms of adsorption to the air-water interface, together with studies of dynamic respreading after monolayer collapse and surface tension lowering in dynamically compressed spread films and dispersions. Results showed that several ether-amide phosphonolipids had more rapid adsorption and improved dynamic respreading behavior compared to DPPC, plus the ability to lower surface tension into the range of less than 1 to 4 mN/m in spread films and in dispersions under dynamic conditions. In combination with a series of diether phosphonolipids synthetized in a companion study [1], these ether-amide compounds are useful in the development of molecular structure-surface activity correlates for lung surfactant-related materials, and should assist in investigating the specificity of interactions between phospholipids and other pulmonary biological molecules.     

Nucleotide sequence of the Escherichia coli micA gene required for A/G-specific mismatch repair: identity of micA and mutY.

The Escherichia coli methylation-independent repair pathway specific for A/G mismatches has been shown to require the gene product of micA. Extracts prepared from micA mutants do not form an A/G mismatch-specific DNA-protein complex and do not contain an A/G mismatch-specific nicking activity. Moreover, a partially purified protein fraction containing both A/G mismatch-specific nicking and binding activities restores repair activity in micA mutant extracts. The DNA sequence of a 2.3-kb fragment containing the micA gene has been determined. There are two open reading frames (ORF) in this DNA fragment: one ORF encodes a 25.7-kDa protein whose function is still unknown, the other ORF codes for a protein with an Mr of 39,147, but this ORF can be transcribed and the mRNA can be translated to yield a protein with an apparent Mr of 36 kDa on a sodium dodecyl sulfate-polyacrylamide gel. Deletion analysis showed that this 39.1-kDa ORF is the micA gene as judged by the capacity of the encoded protein to restore the A/G mismatch-specific nicking activity of micA mutant extracts. Furthermore, our results suggest that micA is the same gene as the closely mapped mutY, which encodes the A/G mismatch-specific glycosylase.     

Adenine affects the structure and stability of telomeric sequences.

Adenine occurs in the strand containing repeated G clusters in the telomeric DNA of a variety of organisms, including that of humans. The role of adenine has been investigated by constructing two sets of oligonucleotides each with one, two, or four copies of the telomeric sequence dTTTAGGG together with a control sequence in which T replaces the A residue, dTTTTGGG. Comparison of the stability and spectral properties of these two sequences in the presence of Na+ or K+ affords a basis for defining the role of adenine in these structures. In Na+, the A residue stabilizes the structure formed by each oligomer significantly, presumably by a base-pairing interaction with T. In K+, by contrast, there is little difference in stability. In two- and four-copy oligomers, the A sequence has a different structure from its T analog, as detected by CD spectroscopy. In the presence of either Na+ or K+, the tetraplexes of A and T interact with intercalators.     

Mechanism of the irreversible inactivation of mouse ornithine decarboxylase by alpha-difluoromethylornithine. Characterization of sequences at the inhibitor and coenzyme binding sites.

Mouse ornithine decarboxylase (ODC) was expressed in Escherichia coli and the purified recombinant enzyme used for determination of the binding site for pyridoxal 5'-phosphate and of the residues modified in the inactivation of the enzyme by the enzyme-activated irreversible inhibitor, alpha-difluoromethylornithine (DFMO). The pyridoxal 5'-phosphate binding lysine in mouse ODC was identified as lysine 69 of the mouse sequence by reduction of the purified holoenzyme form with NaB[3H]4 followed by digestion of the carboxymethylated protein with endoproteinase Lys-C, radioactive peptide mapping using reversed-phase high pressure liquid chromatography and gas-phase peptide sequencing. This lysine is contained in the sequence PFYAVKC, which is found in all known ODCs from eukaryotes. The preceding amino acids do not conform to the consensus sequence of SXHK, which contains the pyridoxal 5'-phosphate binding lysine in a number of other decarboxylases including ODCs from E. coli. Using a similar procedure to analyze ODC labeled by reaction with [5-14C]DFMO, it was found that lysine 69 and cysteine 360 formed covalent adducts with the inhibitor. Cysteine 360, which was the major adduct accounting for about 90% of the total labeling, is contained within the sequence -WGPTCDGL(I)D-, which is present in all known eukaryote ODCs. These results provide strong evidence that these two peptides form essential parts of the catalytic site of ODC. Analysis by fast atom bombardment-mass spectrometry of tryptic peptides containing the DFMO-cysteine adduct indicated that the adduct formed in the enzyme was probably the cyclic imine S-(2-(1-pyrroline)methyl)cysteine. This is readily oxidized to S-((2-pyrrole)methyl)cysteine or converted to S-((2-pyrrolidine)methyl)cysteine by NaBH4 reduction. This adduct is consistent with spectral evidence showing that inactivation of the enzyme with DFMO does not entail the formation of a stable adduct between the pyridoxal 5'-phosphate, the enzyme, and the inhibitor.     

Characterization of the arginine repressor from Salmonella typhimurium and its interactions with the carAB operator.

Primer extension experiments showed that the argR gene, encoding the arginine repressor in Salmonella typhimurium, is transcribed from a single promoter that is negatively regulated by arginine. A repressor overproducing strain was constructed and the repressor was purified to homogeneity. Gel filtration, sedimentation and cross-linking studies established that the native repressor is a hexamer of identical 17,000 Mr subunits. Gel retardation experiments indicate that the apparent dissociation constant for repressor/carAB operator is 6 x 10(-12) M. These experiments showed that arginine is essential for binding of the repressor to the DNA and that pyrimidine nucleotides have no significant effect on this binding. These results indicate that the effect of pyrimidines on expression of the arginine sensitive "downstream" carAB promoter is not directly mediated by the arginine repressor. These experiments also suggest that a single hexamer binds to the carAB operator, which carries two previously defined "ARG box" sequences that characterize operators for arg genes. Gel retardation experiments with DNA fragments carrying the individual ARG boxes showed that both boxes are required for effective binding of the hexameric repressor to the operator, indicating that the ARG boxes comprise a single binding site for the repressor. Analysis of the potential secondary structure of the arginine repressor does not reveal any of the recognizable structural motifs common to a number of DNA-binding proteins. A combination of DNase I, premethylation interference, depurination and hydroxyl radical footprinting techniques were employed to characterize the interactions of the repressor with the carAB operator, with the results suggesting that the repressor predominantly interacts with A.T residues in this region. Comparative DNA sequence analysis of the known arginine operators of enteric bacteria further indicates that the specificity of interaction may be based more on the precise distance between two defined A.T-rich regions rather than on the specific nucleotide sequence.     

Regulation of Hsp70 function by a eukaryotic DnaJ homolog.

We report that a purified cytoplasmic Hsp70 homolog from Saccharomyces cerevisiae, Hsp70SSA1, exhibits a weak ATPase activity, which is stimulated by a purified eukaryotic dnaJp homolog (YDJ1p). Stable complex formation between Hsp70SSA1 and the permanently unfolded protein carboxymethylated alpha-lactalbumin (CMLA) was assayed by native gel electrophoresis. The affinity of Hsp70SSA1 for CMLA appeared to be regulated by YDJ1p. Significant reduction in both CMLA-Hsp70SSA1 complex formation and the release of CMLA pre-bound to Hsp70SSA1 was observed only in the presence of both YDJ1p and ATP. Thus, Hsp70SSA1 and YDJ1p interact functionally in the execution of Hsp70SSA1 chaperone activities in the eukaryotic cell.