Knockout of SlERF.F4 transcription factor enhances drought resilience in tomato

Abstract Since plants are constantly exposed to ever-changing climate conditions, they evolved an intricate system that perceives environmental stresses and integrates them in order to adapt their response. At a molecular level, transcription factors play an important role in regulating the plant’s response by influencing expression of stress responsive genes, and in particular ethylene-responsive factors (ERFs) represent the final components of the transduction pathway of ethylene, a phytohormone involved in many physiological and stress-dependent mechanisms. Among the ERFs that respond to abiotic stresses, we aimed at elucidating the role of SlERF.F4 gene in the response to drought stress in tomato cv. Microtom through a CRISPR/Cas9 mediated knockout. We therefore characterised homozygous Slerf.f4 plants derived from a CRISPR/Cas9-edited line from a physiological, molecular and biochemical point of view during a 7-day water deprivation experiment. A water saving behaviour was observed in T 2 generations evaluated in separate experiments. Compared to the wild-type controls, the analysed Slerf.f4 mutant line displayed reduced stomatal conductance and transpiration rate, leading to higher soil relative water content and indicating a water saving behaviour consistent with a drought avoidance strategy. Moreover, during water stress Slerf.f4 mutants showed a higher leaf concentration of photosynthetic pigments (particularly chlorophyll a , carotenoids and xanthophylls) than wild-type plants, suggesting a better drought stress coping capacity in mutants.