Targeting the tomato fruit epidermis using the nsLTP2 promoter: a molecular tool to study the composition, architecture and properties of the cuticle

Summary Background The cuticle is a hydrophobic polymeric assembly covering the surface of the aerial parts of plants. In the tomato fruit ( Solanum lycopersicum ), the cuticle is involved in many agronomically important traits, such as fruit brightness, resistance to cracking or shelf life. The development of a molecular tool targeting cuticle-associated genes in tomato fruit epidermis could considerably advance our understanding of the relationship between the structure of the cuticle and its functional properties. Results According to its expression profile, the non-specific Lipid Transfer Protein 2 promoter ( pronsLTP ) was selected and its application as a molecular tool for targeting modifications in the epidermis of tomato fruit was validated. Indeed, fluorescence analysis confirmed that pronsLTP activity is associated with the fruit epidermis and coincides with cuticle accumulation. In addition, edition using a CRISPR tissue-specific knockout approach (CRISPR-TSKO) of the carotenoid SlPSY1 gene via pronsLTP showed a high mutation frequency only in the fruit exocarp and mesocarp. Furthermore, overexpression of the flavonoid regulatory gene SlMYB75 under the control of pronsLTP resulted in targeted accumulation of anthocyanins in the exocarp of growing fruit, associated with a change in cuticle composition and permeability. Conclusions Altogether, our results provide a new molecular tool essential for delineating the functional role of cuticle components and opens new perspectives for the targeted engineering of cuticle-related traits to improve fruit quality and agronomical properties.