CRISPR-Cas9 Mediated Knockout of the SlERF8 Transcription Factor Enhances Osmotic Stress Tolerance in Solanum lycopersicum

Drought and soil salinity are major abiotic stresses that limit agricultural productivity globally. Solanum lycopersicum (tomato) is particularly vulnerable to water deficit during vegetative and reproductive stages. In this study, we utilized the CRISPR-Cas9 system to target the SlERF8 gene, a member of the Ethylene Response Factor superfamily, hypothesized to function as a negative regulator of abiotic stress responses. We successfully generated stable homozygous knock-out mutant lines (erf8-1 and erf8-2) exhibiting frameshift mutations at the target locus. Under simulated drought conditions using PEG-6000 and salinity stress (150 mM NaCl), the knock-out lines showed significantly higher relative water content (RWC), reduced electrolyte leakage, and lower malondialdehyde (MDA) accumulation compared to wild-type (WT) plants. Chlorophyll fluorescence analysis (Fv/Fm) indicated preserved photosynthetic efficiency in the mutants under stress conditions. Furthermore, expression analysis of stress-responsive marker genes, including SlCOR47 and SlTAS14, was significantly upregulated in the mutant lines. Our findings demonstrate that CRISPR-Cas9 mediated deletion of SlERF8 enhances osmotic stress resilience by activating downstream osmoprotectant pathways and preserving physiological homeostasis. This study provides a genetic target for breeding drought-resilient tomato cultivars.