Genetic transformation of apple (Malus pumila Mill.) using a disarmed Ti-binary vector

The disamed Ti-binary vector pBIN 6 in Agrobacterium tumefaciens has been used in leaf disc transfomations to produce transgenic apple (Malus pumila Mill.) plants with a nomal phenotype except for a somewhat reduced capacity to root. The presence of the genes for nopaline synthase and neomycin phosphotrans ferase (conferring kanamycin resistance), inserted into the host genome by the vector, was confirmed by Southern blot analysis, the detection of nopaline synthase activity and rooting in the presence of the antibiotic.The nopaline synthase gene continued to be expressed in glasshouse-grown plants several months after removal from in vitro growth conditions.     

The immunogenicity of VP7, a rotavirus antigen resident in the endoplasmic reticulum, is enhanced by cell surface expression.

The glycoprotein VP7, the major serotype antigen of rotaviruses, is localized to the endoplasmic reticulum (ER) of the cell, where it is retained as a membrane-associated protein before assembly into mature virus particles. Wild-type VP7 expressed by a recombinant vaccinia virus was also located internally and was poorly antigenic. Using recombinant techniques, a correctly processed, secreted form of VP7 (S.C. Stirzaker and G.W. Both, Cell 56:741-747, 1989) was modified by addition to its C terminus of the membrane anchor and cytoplasmic domains from the influenza virus hemagglutinin. The hybrid protein was directed to the surface of cells, where it was anchored in the plasma membrane. When expressed in mice and rabbits by a recombinant vaccinia virus, the surface-anchored antigen stimulated a level of rotavirus-specific antibodies that was greater than 100-fold above the level induced by wild-type VP7. T-cell responses to the novel antigen were also elevated in comparison with the wild-type, intracellular protein. Cell surface anchoring may provide a strategy to increase the immunogenicity of intracellular antigens from other parasites and viruses.     

Human non-lineage antigen,CD46 (HuLy-m5): purification and partial sequencing demonstrates structural homology with complement-regulating glycoproteins

CD46, until recently known as HuLy-m5, is a non-lineage restricted surface antigen ubiquitously expressed by almost all human cells except erythrocytes. The CD46 antigen is identified by the E4.3 monoclonal antibody (mAb) and exists at the surface of human peripheral blood lymphocytes (PBLs) as two acidic, non-disulfide bonded chains, and , ofM _r 66 000 and 56 000. Receptor density analysis showed that CD46 was of moderately low abundance on PBLs with 7.5×10³ molecules present on each cell. The two chains of CD46 were purified (144 000-fold) by immunoaffinity-chromatography with E4.3 mAb from the plasma membranes of a human spleen infiltrated with chronic myelogenous leukemia cells. Amino acid sequence analysis of the NH₂-terminal of both and chains yielded the same sequence; XEEPPQ/TFEAMELIGKPKPYYEIGE. Peptide mapping studies confirmed that both CD46 chains were closely related, except for one peptide fragment. This amino acid sequence is identical to that of the NH₂-terminal of the recently cloned membrane co-factor protein (MCP), a membrane protein that binds the C3b and C4b fragments of complement and acts as a co-factor for I protein-mediated decay of the complement convertases. CD46 shares a cross-reactive epitope with some primate retroviruses, and this may indicate that some retroviruses mimic the mechanisms used by autologous human cells to evade complement-mediated immune clearance. Offprint requests to: I. F. C. McKenzie.     

Photobleaching in the unicellular green alga Dunaliella parva 19/9

The change in the pigment composition of the unicellular alga Dunaliella parva 19/9 during exposure to high light (4000 mol m^-2 s^-1) has been investigated. During photobleaching the carotenoids were lost at a greater rate than the chlorophylls. In these photoinhibitory conditions, -carotene and especially the minor carotenes, - and -carotene, were more susceptible to oxidative destriction than the xanthophylls. Lutein, the major carotenoid present, was the most stable of the carotenoids in these conditions. In addition to the direct photobleaching of carotenoids and chlorophylls, high light treatment induced the de-epoxidation of violaxanthin to antheraxantin and zeaxanthin. Small amounts of zeaxanthin were present in cells prior to illumination but the amount increased 2.4 fold following high light treatment. The effects of extremes of temperature during exposure to high light intensities were also investigated. The destruction of chlorophylls was found to be more temperature sensitive than that of the carotenoids. The general pattern of loss for the individual carotenoids was similar to that found at 25°C, i.e., the carotenes were more readily degraded than the xanthophylls.