The regulation and impact of mRNA m⁶A methylation during the expansion and ripening of tomato fruits under various abiotic stresses

N⁶-methyladenosine (m⁶A), the most prevalent modification observed in eukaryotic messenger RNAs (mRNAs), plays a crucial role in plant development and abiotic stress responses. However, its role in tomato (Solanum lycopersicum) fruit expansion and ripening under abiotic stress remains unexplored. In this study, we comprehensively analyzed the changes in m⁶A levels and the expression patterns of m⁶A-modified genes associated with fruit expansion and ripening processes of tomato plants exposed to drought, salt, heat, or cold stress. During fruit expansion under stress conditions, m⁶A methylation modulated the expression of genes associated with the cell cycle and auxin signaling pathways, leading to reduced fruit size. During fruit ripening under stress conditions, m⁶A methylation modulated the expression of genes associated with transcription factors, ethylene biosynthesis and signaling, and lycopene biosynthesis, accelerating fruit ripening under drought, salt, or heat stress, but delaying it under cold stress. Notably, m⁶A methylation modulated mRNA stability to regulate the transcript levels of key genes involved in tomato fruit expansion and ripening under stress conditions. Collectively, these results deepen our understanding of m⁶A methylation's role in fruit expansion and ripening of tomatoes in response to abiotic stress, providing a firm foundation for further investigation of its critical regulatory functions.