High throughput genetic transformation mediated by Agrobacterium tumefaciens in maize

A high throughput genetic transformation system in maize has been developed with Agrobacterium tumefaciens mediated T-DNA delivery. With optimized conditions, stable callus transformation frequencies for Hi-II immature embryos averaged approximately 40%, with results in some experiments as high as 50%. The optimized conditions include N6 medium system for Agrobacterium inoculation, co-cultivation, resting and selection steps; no AgNo₃ in the infection medium and adding AgNo₃ in co-cultivation, resting and selection medium; Agrobacterium concentration at 0.5×10⁹ c.f.u. ml^–1 for bacterium inoculation; 100 mg l^–1 carbenicillin used in the medium to eliminate Agrobacterium after inoculation; and 3 days for co-cultivation and 4 days for resting. A combination of all of these conditions resulted in establishing a high throughput transformation system. Over 500 T₀ plants were regenerated and these plants were assayed by transgene expression and some of them were also analyzed by Southern hybridization. T₁ plants were analyzed and transmission of transgenes to the T₁ generation was verified. This represents a highly reproducible and reliable system for genetic transformation of maize Hi-II.     

Immobilization of the acylase from Escherichia coli on glyoxyl-agarose gives efficient catalyst for the synthesis of cephalosporins

The catalytic properties of penicillin G acylase (PGA) from Escherichia coli, when used in kinetically controlled N-acylation (kcNa) of cephalosporanic nuclei, can be strongly influenced by the moiety in 3-position of the cephem structure. In the synthesis of Cefonicid (1c), the adsorption of the cephalosporanic nucleus (7-SACA) in the PGA active site appeared sensitively increased by a positive ionic interaction between an arginine (ArgA145) in the enzyme active site and the sulphonic group of the β-lactam structure. Interestingly, when PGA was immobilized on solid supports, any effect depending on the substrate structure resulted minimized; the catalytic properties of this enzyme were affected with different outcomes depending on the type of matrix and binding chemistry. The PGA immobilized on glyoxyl-agarose (hydrophilic support activated with aldehyde groups) resulted in a good catalyst when used in kinetically controlled N-acylation of different cephalosporanic nuclei. This derivatives allow much better Vs/Vh(1) (defined as the ratio between the rate of synthesis and the rate of hydrolysis of the acylating agent) than the same enzyme immobilized on Eupergit C, an acrylic hydrophobic supports activated with epoxy groups. The synthetic performances of the Eupergit derivative versus different nuclei were always much poorer if compared with glyoxyl-agarose or the soluble protein. The use of PGA immobilized on glyoxyl-agarose allowed the development of efficient processes for the preparation of Cefazolin in high yield and purity. The results obtained in the optimization of this process are presented.     

Expression of Wiskott-Aldrich syndrome protein in dendritic cells regulates synapse formation and activation of naive CD8+ T cells

The Wiskott-Aldrich syndrome protein (WASp) is a key regulator of actin polimerization in hematopoietic cells. Mutations in WASp cause a severe immunodeficiency characterized by defective initiation of primary immune response and autoimmunity. The contribution of altered dendritic cells (DCs) functions to the disease pathogenesis has not been fully elucidated. In this study, we show that conventional DCs develop normally in WASp-deficient mice. However, Ag targeting to lymphoid organ-resident DCs via anti-DEC205 results in impaired naive CD8(+) T cell activation, especially at low Ag doses. Altered trafficking of Ag-bearing DCs to lymph nodes (LNs) accounts only partially for defective priming because correction of DCs migration does not rescue T cell activation. In vitro and in vivo imaging of DC-T cell interactions in LNs showed that cytoskeletal alterations in WASp null DCs causes a reduction in the ability to form and stabilize conjugates with naive CD8(+) T lymphocytes both in vitro and in vivo. These data indicate that WASp expression in DCs regulates both the ability to traffic to secondary lymphoid organs and to activate naive T cells in LNs.     

Stabilization of heterodimeric enzyme by multipoint covalent immobilization: Penicillin G acylase from Kluyvera citrophila

We have developed a strategy for immobilization-stabilization of penicillin G acylase (PGA) from Kluyvera citrophila by controlled multipoint covalent attachment to agarose-aldehyde gels. This enzyme is composed by two dissimilar subunits noncovalently bound. Thus, in this article we establish clear correlations between enzyme stabilization and the multipoint immobilization and/or between enzyme stabilization and the involvement of the two subunits in the attachment of them to the support. We have demonstrated that important thermal stabilizations of derivatives were only obtained through a very intense enzyme-support multipoint attachment involving the whole enzyme molecule. In this way, we have prepared derivatives preserving more than 90% of catalytic activity and being more than 1000-fold more stable than soluble and one-point attached enzyme. In addition, the involvement of the two subunits in the covalent attachment to the support has proved to be essential to develop interesting strategies for reactivation of inactivated enzyme molecules [e.g., by refolding of immobilized PGA after previous unfolding with urea and sodium dodecyl sulfate (SDS)]. (c) 1993 John Wiley & Sons, Inc.     

Characterization of the regulatory elements of the maize P-rr gene by transient expression assays

The maize P-rr gene conditions floral-specific flavonoid pigmentation, especially in the kernel pericarp and cob. We analyzed the P-rr promoter by transient expression assays, in which segments of the P-rr promoter were fused to the GUS reporter gene and introduced into maize cells by particle bombardment. A basal P-rr promoter fragment (–235 to +326) gave low, but significant, levels of GUS reporter gene expression. Interestingly, two widely spaced segments containing enhancer-like activity were found. When tested individually, both the proximal (–1252 to –236) and distal (–6110 to –4842) segments boosted expression of the basal P-rr promoter::GUS construct about five-fold. A 1.6 kb segment of the P-rr promoter (–1252 to +326) containing the proximal enhancer and the 5-untranslated leader driving the GUS reporter gene showed preferential expression in BMS and embryogenic suspension cell cultures vs. endosperm-derived suspension cell cultures. These results demonstrate the application of transient assay techniques for the identification of regulatory elements responsible for floral-specific regulation of the complex P-rr gene promoter in maize.     

Penicilin acylase mediated synthesis of formyl cefamandole

Summary Penicillin acylase-catalyzed synthesis from D,L-methyl mandelate (1c) and the cefalosporin nucleus (2) at pH 6 gives rise preferentially to the L-diastereoisomer (3a) of cefamandole, whereas D,L-O-formyl methyl mandelate (1f) affords exclusively O-formyl cefamandole (cefamandole nafate) (4), in 30–35% yields.     

pH dependence of the baker's yeast conversion of 4-benzoyloxy-crotonaldehyde into the 1-benzoate of (2R) 1,2,4-butanetriol

In the baker's yeast mediated conversion of 4-benzoyloxycrotonaldeyde (5) ito the 1-benzoate of (2R) 1,2,4-butanetriol (7) there is a market dependence of the ee values from the pH, nearly racemic materials being obtained over pH 4.6.     

Restriction fragment length polymorphism and allozyme linkage map of Cuphea lanceolata

Summary Cuphea lanceolata Ait. has had a significant role in the domestication of Cuphea and is a useful experimental organism for investigating how medium-chain lipids are synthesized in developing seeds. To expand the genetics of this species, a linkage map of the C. lanceolata genome was constructed using five allozyme and 32 restriction-fragment-length-polymorphism (RFLP) marker loci. These loci were assigned to six linkage groups that correspond to the six chromosomes of this species. Map length is 288 cM. Levels of polymorphism were estimated for three inbred lines of C. lanceolata and an inbred line of C. viscosissima using 84 random genomic clones and two restriction enzymes, EcoRI and HindIII. Of the probes 29% detected RFLPs between C. lanceolata and C. viscosissima lines. Crosses between these species can be exploited to expand the map.