GAI Functions in the Plant Response to Dehydration Stress in Arabidopsis thaliana

DELLA (GAI/RGA/RGL1/RGL2/RGL3) proteins are key negative regulators in GA (gibberellin) signaling and are involved in regulating plant growth as a response to environmental stresses. It has been shown that the DELLA protein PROCERA (PRO) in tomato promotes drought tolerance, but its molecular mechanism remains unknown. Here, we showed that the <i>gai-1</i> (gibberellin insensitive 1) mutant (generated from the <i>gai</i>-<i>1</i> (L<i>er</i>) allele (with a 17 amino acid deletion within the DELLA domain of GAI) by backcrossing <i>gai</i>-<i>1</i> (L<i>er</i>) with Col-0 three times), the gain-of-function mutant of GAI (GA INSENSITIVE) in <i>Arabidopsis</i>, increases drought tolerance. The stomatal density of the <i>gai-1</i> mutant was increased but its stomatal aperture was decreased under abscisic acid (ABA) treatment conditions, suggesting that the drought tolerance of the <i>gai-1</i> mutant is a complex trait. We further tested the interactions between DELLA proteins and ABF2 (abscisic acid (ABA)-responsive element (ABRE)-binding transcription factors) and found that there was a strong interaction between DELLA proteins and ABF2. Our results provide new insight into DELLA proteins and their role in drought stress tolerance.