AtGASA1 positively regulates Arabidopsis response to salt stress by suppressing accumulation of reactive oxygen species

AtGASA1 is a member of the gibberellin acid-stimulating protein (GASA) family, characterized by a GASA domain containing 12 conserved cysteine-rich peptides (CRP). Its homologous genes are known to play an essential role in plant responses to both biotic and abiotic stresses; however, the function of AtGASA1 remains unclear. In this study, we found that AtGASA1 is involved in regulating plant growth, leaf expansion and flowering time. Moreover, various results showed that gasa1 mutants exhibited sensitivity to salt stress, while overexpression of AtGASA1 conferred increased resistance to salt stress. To explore the role of conserved cysteine residues within the GASA domain, site-directed mutagenesis was performed to substitute Cys-40 and Cys-44 with alanine. Functional assays in a yeast heterologous expression system showed that yeast expressing AtGASA1C40,44A displayed reduced tolerance to salt stress compared with yeast expressing non-mutated AtGASA1, indicating that these residues are critical for salt stress adaptation. Consistently, transgenic Arabidopsis plants overexpressing AtGASA1C40,44A accumulated higher levels of ROS compared with 35S::GASA1 plants. Collectively, our findings demonstrate that AtGASA1 positively regulates salt stress tolerance in Arabidopsis by reducing ROS accumulation.