Histone H3K9 acetylation modulates gene expression of key enzymes in the flavonoid and abscisic acid pathways and enhances drought resistance of sea buckthorn

Abstract The effect of histone H3K9 acetylation modification on gene expression and drought resistance in drought‐resistant tree species is not clear. Using the chromatin immunoprecipitation (ChIP) method, this study obtained nine H3K9 acetylated protein‐interacting DNAs from sea buckthorn seedlings, and the ChIP sequencing result predicted about 56,591, 2217 and 5119 enriched region peaks in the control, drought and rehydration comparative groups, respectively. Gene functional analysis of differential peaks from three comparison groups revealed that 105 pathways were involved in the drought resistance process, and 474 genes were enriched in the plant hormone signaling transduction pathways. Combined ChIP‐seq and transcriptome analysis revealed that six genes related to abscisic acid synthesis and signaling pathways, 17 genes involved in flavonoid biosynthesis, and 15 genes involved in carotenoid biosynthesis were positively regulated by H3K9 acetylation modification under drought stress. Under drought stress conditions, the content of abscisic acid and the expression of related genes were significantly up‐regulated, while the content of flavonoids and the expression of key enzymes involved in their synthesis were largely down‐regulated. Meanwhile, after exposure to histone deacetylase inhibitors (trichostatin A), the change of abscisic acid and flavonoids content and their related gene expression were slowed down under drought stress. This study will provide an important theoretical basis for understanding the regulatory mechanisms of histone acetylation modifications in sea buckthorn drought resistance.