Cold stress adversely impacts tomato (Solanum lycopersicum) production, particularly in temperate regions, by impairing growth, development, and yield. Abscisic acid (ABA), a key phytohormone, plays a central role in mediating tomato’s response to cold stress through a complex crosstalk network with other hormones and signaling molecules. This review examines ABA’s interactions with hormones such as ethylene, jasmonates, auxin, gibberellins, salicylic acid, brassinosteroids, and strigolactones, as well as signaling molecules like hydrogen peroxide, nitric oxide, hydrogen sulfide, and calcium. These interactions regulate various physiological processes, including osmolyte accumulation, membrane stability, and oxidative stress mitigation, and influence the expression of cold-responsive genes, such as CBFs, COR, and LEA. Critical knowledge gaps remain, particularly in understanding ABA’s context-specific interactions with other hormones and the integration of calcium signaling with ABA pathways under cold stress. By synthesizing current research, this review enhances our understanding of tomato’s cold stress response and provides insights for genetically improving cold tolerance, supporting sustainable tomato production amid climate challenges.

Tomato (Solanum lycopersicum) is highly susceptible to both high and low temperatures, which threaten its growth, yield, and quality. Ascorbate peroxidase (APX) plays a pivotal role in plant responses to abiotic stresses. In this study, we unveil the positive involvement of heat- and cold-induced SlAPX2 in bolstering tomato resilience to temperature extremes. Knockout of SlAPX2 using the CRISPR/Cas9 technique exacerbated oxidative stress under heat and cold conditions, as evidenced by reduced Fv/Fm and increased electrolyte leakage (REL), malondialdehyde (MDA) content, and hydrogen peroxide (H₂O₂) levels. Furthermore, SlAPX2 expression was modulated by abscisic acid (ABA), and the transcription factor ABF4 in the ABA signaling pathway positively regulated SlAPX2 transcription. Using yeast one-hybrid (Y1H) and dual luciferase (LUC) assays, we found that ABF4 directly bound to the SlAPX2 promoter, thereby activating its transcription. Additionally, silencing of SlABF4 compromised tomato’s tolerance to heat or cold. Collectively, these findings reveal a regulatory module, SlABF4–SlAPX2, that enhances tomato tolerance to temperature extremes by detoxifying excessive reactive oxygen species (ROS). This study advances our understanding of ABA-mediated stress responses and highlights the SlABF4–SlAPX2 module as a promising target for breeding temperature-resilient tomato cultivars.

Autophagy, an evolutionarily conserved process for cellular component degradation and recycling, occurs in yeasts, animals, and plants under both stress and normal conditions. However, the functions of autophagy-related genes (ATGs) in watermelon (Citrullus lanatus) remain uncharacterized. In this study, a phylogenetic analysis identified 27 ATGs belonging to 16 subfamilies in the watermelon genome. A promoter analysis revealed that all the ClaATGs contain multiple photo-responsive elements. Tissue-specific expression profiling showed diverse expression patterns of ClaATGs across different tissues, except for the constitutively expressed ClaATG6. Exogenous independent treatments with glucose, naphthalene acetic acid, and 6-benzylaminopurine induced the expression of most ClaATGs, particularly members of the ClaATG8 subfamily, in the graft unions of normal and etiolated seedlings. A sugar application significantly increased autophagosome numbers during the early stages of graft interface healing, accompanied by the upregulation of ClaATG6, ClaATG8b, ClaATG8i, and ClaTOR, as well as the downregulation of ClaSnRK1. These findings elucidate the roles of ATGs in watermelon graft union formation and provide novel insights into the complex functions of autophagy in plant development and stress responses.