Improvement of Drought Resistance through Manipulation of the Gibberellic Acid Pathway

Improving plants' ability to survive under drought is of great importance to the horticultural industry. The plant hormone gibberellic acid (GA) mediates diverse aspects of plant growth and development. The Arabidopsis gibberellin acid insensitive mutant gai-1 displays reduced plant height, altered GA response, and enhanced drought resistance. However, over-expression of gai-1 using the constitutive 35S promoter results in dwarf plants with drought resistance. Here, we tested the hypothesis that the temporary inhibition of cell growth caused by inducible expression of the gai-1 gene would lead to better drought resistance and improve crop productivity without an undesirable dwarf phenotype. We generated transgenic plants in which the gai-1 gene was over-expressed in petunia, under a stress-inducible RD29A promoter from Arabidopsis. When these plants were subjected to limited irrigation and drought treatments, transgenic plants showed phenotypes of darker green leaves and compact flowers compared to the wild type plants. Importantly, these transgenic plants recovered sooner than wild type and the empty vector-transformed control plants. This study provides evidence that temporary inhibition of cell growth caused by over-expression of the gai-1 mutant gene with a drought stress-inducible promoter leads to better drought resistance when the plants experience drought conditions.