A NEW SPECIES OF GENUS HABROPHLEBIODES ULMER (EPHEMEROPTERA: LEPTOPHLEBIIDAE)

Abstract  The present paper deals with a new species Habrophlebiodes zijinensis sp. nov. collected in Nanjing, Jiangsu Povince, China.     

A gene encoding a truncated large subunit of Rubisco is transcribed and salt-inducible in rice

Using the rice salt-tolerant mutant 20 as material, a cDNA library was constructed and two salt-inducible clones, SIR5.5 and SIR8.1, were isolated by differential screening. Homology analysis revealed that the two clones together constituted a chimeric rbcL which encoded a truncated large subunit of Rubisco with 337 amino-acids, plus 64 amino-acids of unknown origin. The expressions of both the normal and the chimeric locus appeared to be developmentally regulated and salt-inducible in shoots of the salt-tolerant mutant 20 and its original variety 77–170. In roots, their expressions were salt-inducible in the salt-tolerant mutant 20 whereas no, or only premature, forms were present in the salt-treated original variety 77–170. Higher concentrations of salt reduced the expressions of both normal rbcL and the chimeric locus. ABA showed no effect on their expression.     

RFLP tagging of a salt tolerance gene in rice

A salt tolerant rice mutant (M-20) was obtained through selection in vitro. Its tolerance was stably inherited over eight generations and most traints between M-20 and its sensitive original 77–170 (Oryza sativa) were very similar. By deriving an F₂ population of M-20 × 77–170 and splitting every F₂ individual into two parts, with one part planted in normal conditions and another part in saline conditions, the inheritance of salt tolerance in rice was studied. Under normal conditions, there was no apparent segregation among F₂ individuals. Under saline conditions, however, the segregation of traits was obvious. According to our standards, the ratio of salt sensitive:moderately-tolerant:tolerant plants was 25:42:18, in accordance with a 1:2:1 ratio. It suggested that the improvement of salt tolerance in our materials was induced by the mutation of a major tolerant gene which showed incomplete dominance. By use of 130 RFLP probes distributed throughout the rice genome, the gene was tagged by a single copy DNA probe, RG4, which was located on chromosome 7. The genetic distance between the salt tolerant gene and RG4 was 7.0 ± 2.9 cM. Based on the split method, a method which could be currently used to evaluate the damage of salt stress in rice was proposed.     

Cell cycle and cell size dependence of susceptibility to hydrodynamic forces

Exposure of animal cells to intense hydrodynamic forces exerted in turbulent capillary flow, and by controiled agitation and aeration, resulted in preferential destruction of S and G(2) cells and the extent of destruction of these cells was dependent upon the intensity of the action. The loss of these cells was possibly due to their larger size. However, the appearance of large numbers of membrane-bound vesicular structures similar to apoptotic bodies as well as cells with low DNA stainability (in a sub-G(1) peak) suggested that the action of adverse hydrodynamic forces on these large cells may at least in part be to induce an apoptotic response. (c) 1995 John Wiley & Sons, Inc.     

Side-chain accessibilities in the pore of a K+ channel probed by sulfhydryl-specific reagents after cysteine-scanning mutagenesis.

To gain insight into the secondary structure of the ion conduction pathway of a voltage-gated K+ channel, we used sulfhydryl-specific reagents of different diameters to probe amino acid side-chain accessibilities in the pore of the channel after cysteine-substitution mutagenesis. We identified five positions at which modified amino acid side chains are accessible from the aqueous lumen of the external channel vestibule. Covalent coupling of the 2-trimethylammonium-thioethyl group to cysteine thiols leads to position-dependent current reduction, suggesting a gradual narrowing of the pore. The fact that the modified side chains of two adjacent amino acids are reactive is not compatible with the ion conduction pathway forming a regular beta-pleated sheet at these positions. The smaller thiol reagent Cd2+ reacts with modified side chains that are also accessible to the larger (2-trimethylammoniumethyl)methanethiosulfate (MTSET) [corrected]. Our results imply that the outer vestibule of a potassium-selective ion channel narrows over a short distance of three amino acids near a position where a regular beta-structure is unlikely.     

Rapid and Sensitive Detection of Xanthomonas fragariae by Simple Alkaline DNA Extraction and the Polymerase Chain Reaction

Methods for DNA preparation from Xanthomonas fragariae in infected or artificially contaminated strawberry plants were compared in diagnostic assays using the polymerase chain reaction (PCR). The bacterium was detected using PCR with primers specific to a region of its hrp gene. Sensitivity of detection was 1.25 ×l 10³ CFU ml^-1 using DNA from bacterial suspensions prepared by an alkali extraction method. This was 10-fold more sensitive than DNA extraction by boiling, and was equal to that in which DNA was prepared by a more involved cetyltrimethylammonium bromide (CTAB) procedure. Sensitivity of detection from artificially contaminated strawberry tissues was 10-fold less than that from cell suspensions. The results indicated that a rapid and simple method of alkali DNA sample preparation is applicable for the sensitive and reliable detection of X. fragariae and possibly other plant pathogenic bacteria.     

The expression of biologically active human p53 in Leishmania cells: a novel eukaryotic system to produce recombinant proteins.

We have investigated the use of Leishmania cells as a novel eukaryotic expression system for the production of recombinant protein. These cells are easy to maintain, requiring no CO2 incubator or shaker, and can be grown in standard tissue culture media. Leishmania cells can be readily transfected with plasmid DNA by electroporation and transformants selected with antibiotic resistance. Recent studies have shown that it is possible to express foreign genes in Leishmania for the purpose of understanding the biology of this protozoan cell. In the present study we report the use of this system as a means of producing a biologically functional human p53 protein. The conformation of the p53 protein is critical for its ability to bind specific DNA sequences. It is demonstrated that Leishmania-synthesized human p53 is phosphorylated and can bind specifically to its enhancer DNA sequence. These data demonstrate that Leishmania may represent a simple eukaryotic expression system for the production of biologically active recombinant proteins.     

应用植物学的研究动向

在一九八一年八月二十一日至二十九日于澳大利亚悉尼召开的“第十三届国际植物学会议”上,应用植物学作为一个学科组共有下列十三项中心议题:1.植物生产力的改进——生理学界线的探讨;2.植物育种的新领域;3.在植物生物学中的细胞培养和体细胞遗传;4.杂草的性质及其起源;5.有利于人类幸福的民族植物学;6.改善旱地作物的水分利用;7.生态系统中的氮素迁移;8.树木营养;9.人工气候室     

Increased production of alpha-amylase by Bacillus amyloliquefaciens in the presence of glycine

The production of alpha-amylase by Bacillus amyloliquefaciens increased by a factor of 300 when glycine was added to a chemically defined simple medium at the early-logarithmic phase of growth. Glycine was not metabolized to a significant extent under the conditions used, but it considerably prevented the lowering of the pH of the culture.