[Transfer of bacterial genes for proline synthesis in plants and their expression by various plant promotors]

Accumulation of free proline (Pro) by bacteria and plants serves as a mechanism protecting these organisms from abiotic stress. We introduced two E. coli genes, proBosm, encoding a mutant variant of the first enzyme of the Pro biosynthetic pathway, gamma-glutamyl kinase, and proA, encoding the second enzyme of the Pro pathway, glutamyl-gamma-semialdehyde dehydrogenase, into tobacco plants. The spontaneous proBosm mutation was selected for Pro overproduction and mapped to the N-terminus of a polypeptide chain; it was found to result from one amino-acid substitution. Two E. coli genes were simultaneously introduced into tobacco plants, each under the control of a strong constitutive CaMV 35S promoter, which contained a duplicated sequence of enhancer, or the root-specific Pmas promoter sequence. Transgenic plants were characterized by Pro overproduction, increased resistance to L-azetidine-2-carboxylic acid (a toxic analog of Pro), and tolerance to salt stress.