SOT2/Growth-Regulating Factor 3 Modulates Salt Tolerance by Regulating Gibberellin-DELLA Signalling

Salinity severely limits plant growth by inducing stress responses that often excessively suppress growth and hinder recovery. Optimising the balance between stress defence and growth is therefore critical for improving plant salt tolerance. Here, we identified a highly salt-tolerant Arabidopsis mutant, salt overly tolerant 2 (sot2), through an forward genetic screen combined with next-generation sequencing. Genetic and functional analyses demonstrated that SOT2 encodes AtGRF3, a Growth-Regulating Factor acting as a negative regulator of salt tolerance. Under salt stress, sot2 plants exhibited enhanced growth, reduced Na⁺ accumulation, and improved ionic homoeostasis compared with Col-0. Loss of AtGRF3 attenuated excessive stress responses, where sot2 plants exhibited lower levels of the stress hormone abscisic acid (ABA) under stress. Mechanistically, AtGRF3 directly binds to the promoter of GA2ox gene under salt stress, promoting gibberellin (GA) catabolism and DELLA protein accumulation. In sot2 plants, lower levels of GA2ox transcripts resulted in reduced DELLA accumulation, which in turn alleviated growth inhibition. These findings reveal AtGRF3 as a key regulator of GA-DELLA signalling in salt stress responses and highlight its potential as a target for improving plant performance under saline conditions.