Transcription Factor RIPENING INHIBITOR and Its Homologs in Regulation of Fleshy Fruit Ripening of Various Plant Species

MADS-domain transcription factor RIPENING INHIBITOR (RIN) is the global regulator of tomato Solanum lycopersicum L. fruit ripening. RIN controls the cascade of fleshy fruit ripening reactions on several levels: it activates the expression of genes encoding other regulation proteins and genes of ethylene biosynthesis (initiation of ethylene-dependent signaling pathways); it directly activates transcription of genes of carotenoid biosynthesis, aroma compounds, carbohydrate metabolism and cell wall-modifying enzymes (by ethylene independent regulation); RIN also involved in epigenetic control of fleshy fruit ripening. Originally discovered in tomato, RIN homologs have now been described for many fleshy fruit crops. The review considers the molecular features of the RIN and homologues MADS-domain transcription factors in different plant species that have similar function of fleshy fruit ripening control and sharing the same evolutionary history. The structure, spatial-temporal expression, and target genes of these regulators are characterized. Using the example of monocotyledonous and dicotyledonous plants that form fleshy fruits, such as tomato, banana, pepper, grape, and strawberry, it has been shown that MADS proteins of the SEPALLATA subfamily play a central role in the complex transcriptional regulation of the ripening cascade of both climacteric and non-climacteric fruits.