Epigenetic Regulations of Fleshy Fruit Development and Ripening and Their Potential Applications to Breeding Strategies

Fleshy fruits, which are only found in Angiosperms, are of high economic importance as they represent an essential component of the human daily diet. True fruits derive from carpels, a leaf-like organ, and their development requires major reprogrammings of gene expression patterns of which we are just starting to grasp the importance of epigenetic regulations. Starting at fruit set, fruit development can be subdivided in two main steps, cell division and cell enlargement, that are followed by ripening in the case of fleshy fruits, whereas dry fruits enter a lignification phase before dehiscence occurs. Here, we summarize the state of the art in epigenetic regulation of fruit initiation, development and ripening with a focus on fleshy fruits. We present evidence that stable epigenetic variations, also called epimutations can affect fruit phenotype and discuss the role of DNA methylation and specific histone post translational modifications at the different fruit developmental phases. Indeed most works so far have been performed on tomato, the model for fleshy fruit studies, but recent works also indicate that epigenetic regulations might be of primary importance in other fruits, although the precise mechanisms might differ. Future research directions required to answer key remaining questions are discussed with the idea to develop breeding strategies that will integrate the epigenetic dimension.