Physiological and transcriptomic evidence revealed the role of exogenous GABA in enhancing salt tolerance in strawberry seedlings

As one of the most salt-sensitive crops, strawberry production is severely limited by salt stress. gamma--aminobutyric acid (GABA) has been reported to play an important role in the immune response of plants. In this study, the physiological and transcriptomic changes in strawberry seedlings treated with GABA under salt stress were investigated to explore the effect of GABA on salt tolerance. The results showed that exogenous GABA maintained high osmolyte levels, increased antioxidant capacity, and decreased the ROS levels in strawberry leaves under salt stress; the MDA was reduced by 3.27-31.46%, with 10 mM being the most significant effect; the total (Spd + Spm)/ Put ratio was upregulated after GABA treatments. More strikingly, the plants treated with 10 mM GABA significantly increased chlorophyll content and net photosynthetic rate in salt-stressed plants, which was explained by the transcriptomic data showing that the expression levels of most of chlorophyll metabolism and photosynthesis-related genes were upregulated. Furthermore, 38 potential TFs belonging to the WRKY, AP2/ERF, and MYB families were identified that may be positively involved in GABA-induced salt tolerance. Co-expressed network analysis revealed that some of these TFs, such as RAP2.7, WRKY46, and MYB306, were significantly positively correlated with chlorophyll metabolism. These findings provide an important basis for the use of GABA in the breeding of strawberry resistant to salt stress.