Epigenomic mechanism regulating the quality and ripeness of apple fruit with differing harvest maturity

Abstract

Harvest maturity significantly affects the quality of apple fruit in post‐harvest storage process. Although the regulatory mechanisms underlying fruit ripening have been studied, the associated epigenetic modifications remain unclear. Thus, we compared the DNA methylation changes and the transcriptional responses of mature fruit (MF) and immature fruit (NF). There were significant correlations between DNA methylation and gene expression. Moreover, the sugar contents (sucrose, glucose, and fructose) were higher in MF than in NF, whereas the opposite pattern was detected for the starch content. The expression‐level differences were due to DNA methylations and ultimately resulted in diverse fruit textures and ripeness. Furthermore, the higher ethylene, auxin, and abscisic acid levels in MF than in NF, which influenced the fruit texture and ripening, were associated with multiple differentially expressed genes in hormone synthesis, signaling, and response pathways (ACS, ACO, ZEP, NCED, and ABA2) that were regulated by DNA methylations. Multiple transcription factor genes involved in regulating fruit ripening and quality via changes in DNA methylation were identified, including MIKCC‐type MADS‐box genes and fruit ripening‐related genes (NAP, SPL, WRKY, and NAC genes). These findings reflect the diversity in the epigenetic regulation of gene expression and may be relevant for elucidating the epigenetic regulatory mechanism underlying the ripening and quality of apple fruit with differing harvest maturity.

Comparison of Fruit Texture and Storage Quality of Four Apple Varieties

“…Starch, found in fruit cells, is crucial for maintaining cell turgor and fruit firmness. In apples, the starch content is a key indicator of harvest maturity [30]. During post-harvest storage, starch is converted into sugar by amylase, which is a vital respiratory substrate in fruits.…”