Integrating ATAC-seq and RNA-seq to reveal the dynamics of chromatin accessibility and gene expression in regulating aril coloration of Taxus mairei

Fruit coloration results from a complex process. Maire yew (Taxus mairei) is an evergreen tree with red, purple, and yellow fruits (arils). While significant progress has been made in understanding pigment biosynthesis in arils, the role of chromatin accessibility in color development remains less well understood. To gain deeper insights into the genetic and epigenetic factors involved, we employed RNA sequencing (RNA-seq) and assay for transposase-accessible chromatin sequencing (ATAC-seq). By integrating the results, we identified 723 differentially expressed genes (DEGs) with chromatin changes in P vs. R, including 312 up- and 411 down-regulated genes. In Y vs. R, we found 159 DEGs, with 97 up- and 62 down-regulated. KEGG enrichment analysis highlighted the flavonoid and carotenoid pathways as major contributors to color variation. When the arils turned purple, the expression levels of C4H, CHS, C3'H, F3'H, F3H, DFR, PSY, PDS, β-OHase, CYP97A3, and LUT1 were significantly up-regulated, while ZDS was down-regulated. The transition to yellow arils was characterized by the up-regulation of F3H, DFR, ZDS, CYP97A3, β-OHase, and LUT1, accompanied by the down-regulation of C4H, CHS, PSY, and PDS. Additionally, 27 transcription factors (TFs) were identified, including MYB, bHLH, and bZIP. These TFs may potentially influence variation in aril color by regulating downstream genes. In total, eight genes were selected for qRT-PCR validation, indicating the reliability of the transcriptome sequencing data. Our results provide in-depth information regarding the coloration of the arils in Maire yew. The study could provide insights for further genetic improvement in Taxus.