Improved Plants
Tobacco - Konstantinova et al 2002
To withstand osmotic stress, which is a common feature of drought, salinity, low and high temperatures, certain plants have evolved high capacity to synthesize and accumulate osmoprotectants or compatible solutes. Being non-toxic, the osmoprotectants are accumulated to osmotically significant levels without disrupting plant metabolism. They fall into several groups- amino acids, quartenary ammonium compounds, polyols and sugars. Their functions range from acting as an energy source to help the cells overcome oxidative stress to acting as an osmoprotectant by stabilising both the quaternary structure of proteins and the highly ordered structure of membranes against the adverse effects of high salinity and extreme temperatures. Various genes, coding for the accumulation of osmoprotectants were introduced into tobacco cultivar in order to improve its abiotic stress tolerance. Tobacco is a model culture for biotechnology studies. It is a relatively drought stress tolerant plant. Konstantinova et al 2002 aimed to use tobacco, which genes were already proven to be involved in improving abiotic stress tolerance, and develop tolerance for low temperatures at early growth stage. This work would be beneficial as most of the crops are planted or sown in the spring and are sensitive to late spring frosts at transplanting stage. The transfer of genes coding for key enzymes of osmolytes biosynthetic pathways appears to be promising for increasing freezing tolerance in tobacco.
Arabidopsis - Yamaguchi-Shinozaki and Shinozaki 2001
This study found that a cis-acting promoter element, the dehydration response element (DRE), plays an important role in regulating gene expression in response to stresses. The transciption factor DREB1A specifically interacts with the DRE and induces expression of stress tolerance genes. Yamaguchi-Shinozaki and Shinozaki showed that overexpression of the cDNA encoding DREB1A in transgenic Arabidopsis plants activated the expression of many of the stress tolerance genes under normal growing conditions and resulted in improved tolerance to drought, salt loading and freezing. However, use of the strong constitutive 35S cauliflower mosaic virus (CaMV) promoter to drive expression of DREB1A also resulted in severe growth retardation under normal growing conditions. In contrast, expression of DREB1A from the stress-inducible rd29A promoter gave rise to minimal effects on plant growth while providing an even greater tolerance to stress conditions than did expression of the gene from the CaMV promoter. As the DRE-related regulatory element is not limited to Arabidopsis the DREB1A cDNA and the rd29A promoter may be useful for improving the stress tolerance of agriculturally important crops by gene transfer.