Dehydration Stress Memory Genes in Tomato (Solanum lycopersicum L.)

Drought is among the most serious abiotic stresses affecting tomato production worldwide, especially under climate change. Plants exposed to repeated drought events may develop stress memory, allowing them to respond more efficiently to subsequent stress exposure. In this study, physiological and transcriptomic tools were combined to investigate dehydration stress memory in tomato (Solanum lycopersicum L.). Tomato plants were subjected to two consecutive drought stresses separated by a recovery stage, where control (C), first stress (S1), rehydration (H), and second stress (S2) stages were analyzed. Physiological measurements showed progressive reductions in relative water content (RWC) and PSII activity under drought stress, while proline accumulation was significantly increased during the second stress stage, indicating memory-associated adaptive responses. RNA sequencing revealed dramatic transcriptome reprogramming with thousands of differentially expressed genes (DEGs) across stress stages. Hierarchical clustering identified 30 distinct expression patterns among revealed DEGs, including clusters associated with transcriptional memory, adaptive responses, metabolic adjustment, and recovery processes. Several memory-associated clusters were enriched with transcription factors, signaling proteins, osmolyte-related genes, and reactive oxygen species detoxification enzymes. Gene Ontology analysis highlighted significant enrichment of pathways related to photosynthesis, response to water deprivation, ABA signaling, oxidative stress, carbohydrate metabolism, and chromatin organization. Recovery-associated expression of histone and chromatin remodeling genes indicates a potential involvement of epigenetic-related regulatory processes in dehydration stress memory in tomato. Tomato plants respond to repeated dehydration stress through coordinated physiological, metabolic, transcriptional, and epigenetic adjustments that improve stress adaptation. The identified candidate memory genes may provide useful targets for future breeding programs aimed at enhancing drought tolerance in tomato.