GENOME-WIDE ANALYSIS OF HISTONE MODIFICATIONS AND ASSOCIATION WITH RIPENING-RELATED GENES DURING POST-HARVEST IN TOMATO FRUIT

Tomato (Solanum lycopersicum L.) is the model system for investigating the molecular basis of ripening in fleshy fruits. Ripening is orchestrated by a complex regulative network including multiple transcription factors, ethylene signaling pathway, and epigenome changes. It is still unclear whether fruit ripening has to be regarded as a process of senescence or as a distinct process. We investigated the biological relevance of histone modifications (HMs) H3K4me3, H3K9/K14ac, and H3K27me3 in fruit post-harvest using ChIP-Seq. H3K4me3 and H3K9/K14ac are histone marks that positively correlate with gene expression while H3K27me3 plays a repressive role. In this study, HMs were mapped in fruit pericarp of Lucariello, a landrace with long shelf-life belonging to 'Pomodorino del Piennolo del Vesuvio DOP'. Three different time points have been analyzed: red ripe fruit (Breaker+8) coincident with the harvest, 60 and 150 days after harvest. HM profiles allowed the genome to be partitioned into eight chromatin states corresponding to regions marked by one HM, co-occurrence of HMs, and unmarked regions. Based on chromatin state changes between time points, 12% of chromatin was estimated to be dynamic during post-harvest, and one-third was related to gain/loss of H3K27me3-only marked regions. We identified differentially enriched peaks of HMs at +/-2kb from predicted transcription start site regions which were correlated with differentially expressed genes including several ripening-related genes. Data gathering and interpretation are now being carried out to identify the relative contribution of HMs to transcriptional regulation in tomato fruit post-harvest.