Generating drought- and salt-tolerant tomato germplasm through bioengineering of the ethylene response factor SlERF.J2.

Drought and salinity are key abiotic constraints limiting the growth, development, and yield of tomato (Solanum lycopersicum). Ethylene response factors are crucial regulators that govern plants' adaptation to diverse abiotic and biotic stress stimuli. Nevertheless, the exact role of SlERF.J2 in abiotic stress resistance remains unclear. In this study, clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 gene-editing technology was used to generate slerf.j2 knockout tomato lines to clarify the biological function of SlERF.J2 in regulating tomato's responses to drought and salt stress. The results revealed that deletion of SlERF.J2 markedly enhanced tomato seedlings' resistance to polyethylene glycol 6000-induced drought, mannitol, and salt stresses. Compared with the wild-type (WT), the knockout lines exhibited significantly increased peroxidase activity and leaf relative water content, as well as markedly decreased contents of hydrogen peroxide and malondialdehyde. After stress treatment, the expression levels of genes associated with the stress response, flavonoid biosynthesis, chlorophyll biosynthesis, light response, cell division, and hormone biosynthesis in SlERF.J2-edited tomato lines were significantly higher than those in WT plants. A yeast one-hybrid assay confirmed the direct interaction between SlERF.J2 and the SlCPS promoter. Collectively, this study clarifies the important function of SlERF.J2 in regulating drought and salt stress tolerance in tomato, providing genetic resources for tomato breeding.