一株广谱中和抗原性出血热病毒株的发现

一株分离自杭州市褐家鼠的出血热病毒Gou_3株的免疫血清对10株I型病毒的中和滴度除二株为160外均为320,而对4株Ⅱ型病毒的滴度为320—640,说明Gou_3株免疫血清对两型毒株中和效价大多数无差异或只差2倍,是一株中和抗原广谱的毒株。用I型和Ⅱ型毒株免疫血清对Gou_3株进行型别检定结果表明Gou_3株是Ⅱ型病毒。     

Inhibition of Sucrose Enhancer Effect of the Potato Proteinase Inhibitor II Promoter by Salicylic Acid

Effect of salicylic acid (SA) on the expression of the potato proteinase inhibitor (PI) II promoter was studied with transgenic tobacco plants (Nicotiana tabacum) carrying a gene fusion between the PI-II promoter and the chloramphenicol acetyltransferase (cat) reporter. As previously observed, the PI-II promoter was inducible by wounding and the promoter activity was further enhanced by sucrose. Addition of SA did not influence the wound induction of the PI-II promoter but significantly inhibited the sucrose response. The 5′-deletion mutant −573 was unable to respond to wounding but did respond to sucrose and SA. The 3′-deletion analysis indicated the presence of a sucrose-responsive element between −574 and −520. A study of the insertion mutants revealed the function of another sucrose-responsive element between −522 and −500. Enhancer effects of these sucrose-responsive elements were inhibited by SA. These studies suggest that SA inhibits PI-II promoter activity by decreasing the sucrose response. Analysis of SA-related chemicals revealed that only acetyl-SA showed a similar inhibitory effect, and other hydroxybenzoic acids had little or no effect on the sucrose enhancer activity. Therefore, it seems that the interaction between SA and the receptor molecule is specific.     

Diversity and origins of endophytic fungal symbionts of the North American grass Festuca arizonica

Summary Acremonium spp. endophytes are mutualistic fungal symbionts of many C3 grasses. They are anamorphs of Epichloë typhina (Clavicipitaceae) that have become strictly seedborne, heritable components of symbiotic units (symbiota). In order to test the possibility that endophytes may contribute to the genetic diversity of symbiota, a survey was conducted of plants from nine populations of Festuca arizonica in the southern Rocky Mountains. Sequence analysis of rRNA gene segments distinguished three Acremonium endophyte types. Parsimony analysis indicated at least two distinct evolutionary origins of the Acremonium endophytes from E. typhina. Either or both of these evolutionary lineages may have involved cospeciation with the host.     

Isolation and sequence analysis of the genomic DNA fragment encoding an aspartic proteinase inhibitor homologue from potato (Solanum tuberosum L.)

A genomic DNA clone encoding an aspartic proteinase inhibitor of potato was isolated from a lambda EMBL3 phage library using the aspartic proteinase inhibitor cDNA as a hybridization probe. The gene has all characteristic sequences normally found in eucaryotic genes. Typical CAAT and TATA box sequences were found in the 5-upstream region. In this part are also two putative regulatory AGGA box sequences located. In the genomic sequence there are no intron sequences interrupting the coding region. An open reading frame of the gene encodes a precursor protein of 217 amino acids which shows high percent identity with the aspartic proteinase inhibitor cDNA.     

The stability of foreign protein production in genetically modified plant cells

Summary The stability of foreign protein production in genetically engineered plant cells was studied. A cultured tobacco cell line was transformed with a chimeric molecule carrying a bacterial gene, ß-glucuronidase (GUS), under plant regulatory sequences. The specific GUS activity was monitored for 294 days with ten independently transformed cell lines either in the presence or the absence of selectable antibiotics. Specific GUS activity was stably maintained in five lines. About a two-to four-fold increase in the GUS activity was observed from three cell lines. The remaining two cell lines lost the activity within the first 70 to 210 days. The presence of antibiotics did not significantly alter the stability of the foreign protein production in all cell lines examined.     

Cultivation of plant cells in a stirred vessel: effect of impeller design

Suspension cultures of Nicotiana tabacum were grown in a batch fermentor using different agitation systems. The effects of the impeller type, size, and agitation speed on the productivity of cell mass and secondary metabolites (phenolics) have been investigated. The use of a large, flat-bladed impeller (diameter 7.6 cm; width 14.0 cm) improved culture growth significantly over systems using a regular, flat-bladed impeller (diameter 5.6 cm; width 1.5 cm). An impeller of the same dimensions as the 14.0-cm-wide, large, flat-bladed impeller with sail cloth blades yielded a higher maximum growth rate in the exponential phase but resulted in a longer lag phase. Overall (intracellular and extracellular) phenolics concentration showed a direct relationship to culture growth rate whereas extracellular concentrations were a function of agitation conditions. Power consumption and flow pattern studies were also completed to further characterize the different impellers tested.     

Conformation and structure of 2-amino-8-(β-d-ribofuranosyl)imidazo [1,2-a]-s-triazin-4-one (5-aza-7-deaza guanosine), a potent antiviral nucleoside

The crystal and molecular structure of one imidazo[1,2-a]-s-triazine nucleoside and its antiviral activity are described. The crystal structure of 2-amino-8-(β-d-ribofuranosyl)imidazo-[1,2-a]-s-triazin-4-one monohydrate (C₁₀H₁₃N₅O₅·H₂O) was solved by X-ray counter data. The compound crystallizes in the monoclinic space group P2₁ with cell dimensions a = 7.353 (1), b = 6.465 (1), c = 13.701 (1) Å, β = 104.64 (1)°. The structure was solved by direct methods and refined by full matrix least-squares technique to a final value of the conventional R-factor of 0.049 using 1998 observed intensities. The orientation of the base relative to the sugar ring defined in terms of rotation about the C(1′)-N(8) glycosyl bond is anti (47.8°). The ribose moiety exhibits C(2′)-endo, ²E conformation. The conformation around C(4′)-C(5′) is gauche^?. Molecular packing is dominated by hydrogen bonds. Base stacking occurs long the b axis. 5-Aza-7-deazaguanosine has shown a marked antiviral activity in vitro against herpes simplex virus despite the fact that N(3) is effective as the hydrogen acceptor only.     

Sugar and phosphate metabolism and alkaloid production phases in submerged cultures of two Claviceps strains

Summary In submerged cultures of Claviceps sp. CP II, elymoclavine was synthesized only by the growing mycelium (phase P1), whereas cultures of C. purpurea strain 129 produced agroclavine after vegetative growth had also ceased (phase P2). In strain CP II, the peak of activity of malate dehydrogenase, glucose-6-phosphate dehydrogenase and phosphatases was related to the time of maximum growth rate and alkaloid production. Citrate synthase activity paralleled the course of alkaloid synthesis. Strain 129 exhibited a further activity peak of the same magnitude during phase P2. ATP levels in both cultures corresponded to the pattern of change in enzyme activities. Strain CP II contained roughly twice as much orthophosphate and ATP in its cells as strain 129 and exhibited higher average activity of glucose-6-phosphate dehydrogenase. It follows from these results that alkaloid synthesis requires the processes of primary metabolism, even when it occurs after active growth of the culture has ceased. Cultures producing alkaloids oxidized at C-8 exhibit higher glucose-6-phosphate dehydrogenase activity, probably because of a higher NADPH consumption.