绿色杜氏藻转录组分析

为了深入了解绿色杜氏藻(Dunaliella viridis)基因信息及功能、耐盐相关通路(甘油脂代谢)及关键酶,本文首次通过Illumina HiSeq^TM 2000高通量测序技术对绿色杜氏藻转录组进行测序,利用Trinity软件将数据组装形成转录本,对所有转录本进行COG(Clusters of Orthologous Groups)、GO(Gene Ontology)和KEGG(Kyoto Encyclopedia of Genes and Genomes)分类和功能注释、Pathway注释以及蛋白编码区(Opening reading fragment,ORF)的预测,并对甘油脂代谢通路关键酶基因进行了分析。转录组测序共获得81 593个转录本,其中ORF共有77 117条,约占所有转录本的94.50%。COG分类结果表明,16 569条转录本被分为24个类别。GO分类结果表明,76 436条转录本被注释。在所有注释分类中,生物学过程转录本数量最多,为30 678条,占总转录本数的40.14%。KEGG分析结果表明,317个标准途径中包含26 428条转录本,含转录本最多的类别是代谢,为9949条(37.65%)。与代谢有关的途径为131条,占所有注释途径的41.32%。在甘油脂代谢通路中仅发现1条关键酶转录本(二羟丙酮激酶),该酶可能与绿色杜氏藻耐盐胁迫中甘油的合成有较大关系。本研究进一步完善了绿色杜氏藻的基因信息,为绿色杜氏藻代谢途径研究奠定了坚实的基础。     

Silver Plated Ribosomes

WE recently reported that dissociation of free 70S ribosomes from E. coli to 30S and 50S subunits could occur during sedimentation in buffer containing K⁺ as the predominant monovalent cation¹. Spermidine at a physiological concentration (1 mM) specifically prevented the dissociation and we suggested that the dissociation that occurred in its absence was due to loss of the polyamine from the 70S ribosome. We have subsequently found that this hypothesis is wrong and that the dissociation that took place in the original experiments was due not primarily to loss of spermidine, but to a reaction with silver present in very small amounts in the AR KCl used in the buffer.     

Chloroplast and Cytoplasmic Ribosomes of Euglena: Selective Binding of Dihydrostreptomycin to Chloroplast Ribosomes

Dihydrostreptomycin binds preferentially to chloroplast ribosomes of wild-type Euglena gracilis Klebs var. bacillaris Pringsheim. The K(diss) for the wild-type chloroplast ribosome-dihydrostreptomycin complex is 2 x 10(-7) M, a value comparable with that found for the Escherichia coli ribosome-dihydrostreptomycin complex. Chloroplast ribosomes isolated from the streptomycin-resistant mutant Sm(1) (r)BNgL and cytoplasmic ribosomes from wild-type have a much lower affinity for the antibiotic. The K(diss) for the chloroplast ribosome-dihydrostreptomycin complex of Sm(1) (r) is 387 x 10(-7) M, and the value for the cytoplasmic ribosome-dihydrostreptomycin complex of the wild type is 1,400 x 10(-7) M. Streptomycin competes with dihydrostreptomycin for the chloroplast ribosome binding site, and preincubation of streptomycin with hydroxylamine prevents the binding of streptomycin to the chloroplast ribosome. These results indicate that the inhibition of chloroplast development and replication in Euglena by streptomycin and dihydrostreptomycin is related to the specific inhibition of protein synthesis on the chloroplast ribosomes of Euglena.     

Influence of temperature and nitrogen concentration on photosynthesis ofDunaliella viridis Teodoresco

The photosynthetic behaviour ofDunaliella viridis has been studied under a combination of three variables: irradiance (0–900 mol m^–2 s^–1), temperature (15, 23, 31, 38, 42 °C) and nitrogen concentration (0.05, 0.5, 1.5, 5, 10 mM NO ₃ ^- ) at a salinity of 2 M NaCl.The highest rates of photosynthesis have been found at 31 °C and a nitrate concentration of 10 mM. There exists a synergistic effect between temperature and nitrogen availability on the photosynthesis ofD. viridis; under nitrogen deficiency oxygen evolution is low, even null at high temperature. The interaction between these two variables of control occurs in a multiplicative way. There is also a general increase in photosynthetic pigments following the increase in nitrogen concentration in the culture medium. The normalization of net photosynthesis data in relation to chlorophylla shows that nitrogen concentration makes an indirect control of the photosynthetic rate ofD. viridis through the variation of pigment concentration.     

Ribosomes,G-factor and Siomycin

G-factor interacts with the 50S ribo-somal subunit at a site which is distinct from the peptidyl transferase centre and which is inactivated by siomycin.     

Thermal Analysis of Bacterial Ribosomes

Ribosomal particles of E. coli were examined by using a heat leakage scanning calorimeter. Remarkable changes were observed in thermograms of 70S ribosomes and their subunits when the Mg²⁺ concentration was raised from 1 mm to 10 mm. It was suggested that ribosomal subunits exist in more than one conformation, and changes in their conformation might be the primary cause of the association-dissociation process of ribosomes. Comparisons of thermograms of RNase- and chymotrypsin-treated, as well as non-treated SOS and 30S subunits suggest that conformational changes in each subunit may be ascribed to changes in rRNA.     

Mitochondrial Ribosomes in HeLa Cells

HeLa cell mitochondria contain 60S ribosomes which seem to consist of subunits of 45S and 35S particles. The 16S and 12S RNA components are coded by mitochondrial DNA.     

The flagellar apparatus ofDunaliella: Isolation of basal body-flagellar root complex

Summary InDunaliella bioculata, a biflagellate wall-less unicellular alga, the cytoskeleton is organized around the two basal bodies. Each basal body is associated with two dissymetric flagellar roots and numerous micro tubules which constitue a regular frame around the cell. We isolated the basal body-flagellar-root apparatus and studied its ultrastructure after negative staining. The two different flagellar roots are formed of microtubules and bundles of twisted filaments 3,5–4 nm in diameter. The proximal end of each root fans out and envelopes the basal body. We have shown preliminary results on the protein composition of basal body-flagellar roots fraction.