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

#### **Zhijuan Wang 1,**†**, Liu Liu 2,3,**†**, Chunhong Cheng 2,3,**†**, Ziyin Ren 1, Shimin Xu 1 and Xia Li 1,\***


Received: 20 December 2019; Accepted: 23 January 2020; Published: 27 January 2020

**Abstract:** 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 *gai-1* (gibberellin insensitive 1) mutant (generated from the *gai*-*1* (L*er*) allele (with a 17 amino acid deletion within the DELLA domain of GAI) by backcrossing *gai*-*1* (L*er*) with Col-0 three times), the gain-of-function mutant of GAI (GA INSENSITIVE) in *Arabidopsis*, increases drought tolerance. The stomatal density of the *gai-1* mutant was increased but its stomatal aperture was decreased under abscisic acid (ABA) treatment conditions, suggesting that the drought tolerance of the *gai-1* 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.

**Keywords:** drought; GA; DELLA; ABF2; protein–protein interaction
