Histone deacetylase MdHDT3 suppresses ethylene biosynthesis by deacetylating MdACS1 and MdACO1 during apple fruit ripening

Apple (Malus domestica) is a climacteric fruit whose ripening is primarily controlled by ethylene. Histone acetylation functions in ethylene biosynthesis during apple ripening, but its underlying molecular mechanisms in ethylene biosynthesis are unclear. Therefore, this study aims to investigate the effects and potential molecular mechanisms of histone modifications in ethylene synthesis during apple fruit ripening. RNA sequencing was performed on apple fruit treated with histone deacetylase inhibitor sodium butyrate to identify histone deacetylases. Additionally, we examined the effects of a specific histone deacetylase on ethylene production and ethylene-related genes. Among the six histone deacetylases identified in the apple fruit, MdHDT3 had the highest expression level during ripening. Treatment with sodium butyrate significantly inhibited MdHDT3 expression and promoted ethylene biosynthesis in apple fruit. Additionally, MdHDT3 suppressed the expression of key genes involved in ethylene biosynthesis (MdACS1 and MdACO1) via deacetylation, thereby negatively regulating ethylene biosynthesis. Conclusively, this study provides insight into the molecular mechanism by which the histone deacetylase MdHDT3 inhibits ethylene synthesis in apple fruit from an epigenetic perspective.