Cloning and expression in Escherichia coli of the Azospirillum brasilense Sp7 gene encoding ampicillin resistance

The Azospirillum brasilense ATCC 29145 gene coding for beta-lactamase was cloned in Escherichia coli. The gene was expressed in E. coli from its own promoter as a 30-kilodalton protein, conferring resistance to high levels of beta-lactam antibiotics. The DNA sequence containing the beta-lactamase gene was found to be highly amplified in the Azospirillum genome, scattered in the chromosomal as well as in the plasmidic DNA.

Lectin in Vegetative Tissues of Adult Barley Plants Grown under Field Conditions

A study of the distribution of lectins over different vegetative tissues of barley (Hordeum vulgare L.) plants, which were grown under normal crop conditions, indicated that lectin occurs in roots, leaves, and developing ears. Isolation and characterization of both root and leaf lectins led to the conclusions (a) that they are indistinguishable from the embryo lectin and (b) that the total lectin content of these vegetative organs is many times higher than that of the embryo. Finally, in vivo labeling experiments demonstrated that the lectin is synthesized de novo in roots and leaves.

A new type of cereal lectin from leaves of couch grass (Agropyrum repens)

Extracts from couch grass (Agropyrum repens) leaves contain relatively high lectin concentrations. Preliminary experiments with crude extracts indicated that the leaf lectin differs from the embryo lectin of the same species and other Gramineae embryo lectins with respect to its sugar and blood group specificity, and serological properties. A comparison of the biochemical, physicochemical and biological properties of purified lectins from couch grass leaves and embryos, and wheat germ agglutinin revealed that the leaf lectin has the same molecular structure as the embryo lectins. It is a dimer composed of two identical subunits, which, however, are slightly larger than embryo lectin subunits. Structural differences between both couch grass lectins were further inferred from in vitro subunit exchange experiments and serological analyses. Whereas the embryo lectin readily forms heterodimers with embryo lectins from other cereal species and also is serologically indistinguishable from them, the leaf lectin does not exchange subunits with the same embryo lectins and is serologically different. In addition, couch grass leaf lectin exhibits specificity for N-acetylgalactosamine and agglutinates preferentially blood-group-A erythrocytes whereas the embryo lectin is not inhibited by N-acetylgalactosamine and exhibits no blood-group specificity. It was observed also that the lectin content of couch grass leaves varies enormously during the seasons.