Epitranscriptomic profiling of cytosine N4 acetylation (ac<sup>4</sup>C) in Solanum lycopersicum and dynamic changes under heat stress condition

N4-acetylcytidine (ac⁴C), which is an evolutionarily conserved RNA modification in eukaryotes, functions as a critical epitranscriptomic regulator that enhances mRNA stability and translation efficiency. In Arabidopsis thaliana and Oryza sativa, ac⁴C has been characterized as a modulator of transcriptome homeostasis that functions by regulating translational efficiency and maintaining RNA structure; however, the distribution patterns and biological functions of ac⁴C in other plant species remain largely unexplored. A transcriptome-wide map of the ac⁴C of Solanum lycopersicum revealed conserved features of plant ac⁴C modification, with preferential enrichment in mRNA translation initiation and termination regions as well as high conservation of modification motifs and functional categories of target genes across species. Notably, heat stress triggered global ac⁴C hyperacetylation, and hypermodified genes were enriched in transcripts encoding photosynthesis and thermotolerance-associated regulators. Multiomics integration further revealed that hyperacetylated and upregulated genes were significantly enriched in stress-response pathways, accompanied by elevated transcription levels. Silencing of SLNAT10 resulted in reduced stability of highly acetylated transcripts under heat stress conditions. These findings reveal that RNA acetylation is synchronized with posttranscriptional regulation that promotes transcriptional reprogramming to establish heat tolerance, providing a mechanism for the epitranscriptomic control of environmental adaptation in plants.