Histone H3K27 Demethylase SlJMJ3 Modulates Fruit Ripening in Tomato.

The histone lysine (K) demethylase 4 (KDM4/JHDM3) subfamily of jumonji domain-containing demethylases (JMJs) has been implicated in various aspects of plant development. However, their involvement in regulating the ripening of fleshy fruits remains unclear. Here, we identified SlJMJ3, a member of the KDM4/JHDM3 family, as a H3K27me3 demethylase in tomato (Solanum lycopersicum) that plays an important role in fruit ripening regulation. Overexpression of SlJMJ3 led to accelerated fruit ripening, whereas loss-of-function of SlJMJ3 delayed this process. Furthermore, we determined that SlJMJ3 exerts its regulatory function by modulating the expression of multiple ripening-related genes involved in ethylene biosynthesis and response, carotenoid metabolism, cell wall modification, transcriptional control, and DNA methylation modification. SlJMJ3 bound directly to the promoters of ripening-related genes harboring the CTCTGYTY motif and activates their expression. Additionally, SlJMJ3 reduced the levels of H3K27me3 at its target genes, thereby up-regulating their expression. In summary, our findings highlight the role of SlJMJ3 in the regulation of fruit ripening in tomato. By removing the methyl group from trimethylated histone H3 lysine 27 at ripening-related genes, SlJMJ3 acts as an epigenetic regulator that orchestrates the complex molecular processes underlying fruit ripening.