Epigenetic changes in the regulation of carotenoid metabolism during honeysuckle flower development

Flower development is one of the most vital pathways in plant development, during which the epigenetic regulation of gene expression is essential. DNA methylation, the most conserved epigenetic modification, participates in gene expression regulation and transposable element silencing. Honeysuckle (Lonicera japonica) is an important medicinal plant renowned for its colorful and fragrant flowers. Honeysuckle flowers change color from white to gold as a result of carotenoid accumulation during development. However, the role of DNA methylation in flower color changes is not well understood in L. japonica. Here, we performed whole-genome bisulfite sequencing and transcriptome sequencing during flowering development in honeysuckle. The results showed that a decrease in the levels of genome-wide average DNA methylation during flower development and changes in DNA methylation were associated with the expression of demethylase genes. Moreover, many genes involved in carotenoid biosynthesis and degradation, such as LjPSY1, LjPDS1, LjLCYE, and LjCCD4, have altered expression levels because of hypomethylation, indicating that DNA methylation plays an important role in flower color changes in honeysuckle. Taken together, our data provide epigenetic insights into flower development and color change in honeysuckles.