Epigenetic regulation during fleshy fruit development and ripening

The development of fleshy fruits is characterized by cell division and expansion events that occur following fertilization. In contrast to dry fruits there is no lignification phase, but fleshy fruits undergo a complex ripening process. Tomato has long been the model for fleshy fruit development and ripening, relying on the establishment and maintenance of differential transcription patterns. A full understanding of fruit development and ripening will not be achieved when it is based only on genetic models. Epigenetic regulations are likely to be essential as well, as recently suggested by the discovery that the tomato Cnr (Colour non-ripening) mutation (characterized by abolishment of fruit ripening) was caused by the hypermethylation of part of the promoter region. Histone marks collaborate with DNA methylation to shape chromatin and suggest a complex interplay between gene transcription and epigenome landscapes. At present, our current understanding of the function of epigenetic marks has been mainly obtained with the model plants Arabidopsis, rice and maize and is by far less advanced in most crop plants. However there is increasing evidence that epigenetic regulations are essential actors that also control traits of agronomical relevance, such as plant adaptation to environmental constraints, and heterosis, a phenomenon extensively used to increase agronomical production, flowering time or fruit quality.