Influence of Developmental Stage and Shading on Apple (Malus domestica) Flesh Polyphenols via Ecophysiological and Epigenetic Mechanisms

Polyphenols are important
components of cultivated apple (Malus domestica). Their contents in the flesh undergo
deep changes during fruit development and ripening. The controls of
these changes are not fully understood and involve many molecular
players. In this work, we investigated the link between polyphenol
profiles (targeted analysis through UPLC-DAD-ESI-TQ), gene expression
patterns, and variations in flesh methylome during development and
ripening while applying shading at specific developmental stages.
Polyphenol changes occurred early during the cell division period
(−74% from unripe to ripe). Gene expression analysis showed
an enrichment of the flavonoid pathway during development and ripening,
which was associated with increased cytosine methylation in the promoter
regions of polyphenol biosynthetic genes. Fruit shading treatments
modified flesh composition only if applied early during the cell division
period. This effect was not entirely maintained at maturity. The multiomics
analysis in dynamics allows us to discuss the underlying mechanisms
controlling fruit metabolism.