Identification of the NCED gene family in tomato (Solanum lycopersicum) and functional analysis of SlNCED2 in response to drought stress

When under drought stress, plants experience hindrances in photosynthesis and cell division, which consequently leads to a decrease in their growth rates. Abscisic acid (ABA) regulates the exchange of water and gases between plants and the external environment by controlling stomatal opening and closing. This hormone plays a significant role in enhancing plant resistance to stressful conditions. Pivotal rate-limiting enzymes involved in the biosynthesis of plant ABA are encoded by genes belonging to the NCED (9-cis-epoxy-carotenoid dioxygenase) family. Therefore, the present study investigated the functions and mechanisms of the tomato NCED gene family in drought resistance. Bioinformatic analysis revealed that the promoters of most SlNCED genes harbored cis-acting elements associated with stress responses. The quantitative reverse transcription-polymerase chain reaction (qRT-PCR) results showed that SlNCED2 may be a key gene in drought stress resistance in this family. After drought treatment, the SlNCED2 silenced tomato plants had significantly diminished ABA and Pro-levels compared to the control plants, the stomatal opening proportion was significantly higher, oxidative stress was more intensive, and drought tolerance was significantly diminished. In addition, SlNCED2 interacted with loxC, a key protein in plant resistance to stress responses. Therefore, the SlNCED2 gene serves as a crucial enhancer of drought tolerance in tomatoes. In summary, this study elucidated the evolutionary patterns and functional distinctions within the NCED family of tomato genes, providing a deeper understanding of the regulatory mechanisms governing plant resistance to drought stress.