New Gene Sources for Development of Agronomic Plants with Tolerances to Drought and Other Abiotic Stresses

This project was an investigation in plant biochemistry/molecular biology/molecular genetics directed toward saving water through the development of water-conserving plants. The central, specific objective was to determine whether the thermophilic eubacterium, Thermus thermophilus HB8, produced one specific enzyme protein responsible for the biosynthesis of a class of compounds newly discovered in higher plants called uncommon polyamines. Uncommon polyamines may be protectants against abiotic stresses such as drought and heat. The rationale of the project was that if the central objective could be achieved, then the gene in T. thermophilus which produced the unique enzyme protein would be a valuable objective for cloning and transfer from the bacterium to plants using recombinant DNA methods. This transfer might confer improved tolerances in plants towards drought and heat stresses. The major conclusions of the project were the following: (i) Numerous criteria based on purification trials of the protein from T.thermophilus indicated that one unique protein is responsible for all uncommon polyamine biosyntheses. (ii) The enzyme protein demonstrated extraordinary catalytic efficiency indicating that it would be an excellent candidate for isolation of its gene and its transfer to plants. (iii) Unexpectedly, plants themselves were discovered to produce this enzyme protein and the uncommon polyamines in preselected drought-tolerant alfalfa and heat-tolerant cotton strains. (iv) Metabolic inhibitors were identified which could be exploited to develop cell selection protocols which may yield crop plants with improved drought tolerances.