Fruit development and ripening is regulated by genetic and environmental factors and is of critical importance for seed dispersal, reproduction, and fruit quality. Tomato () () mutant fruit have a classic ripening-inhibited phenotype, which is attributed to a genomic DNA deletion resulting in the fusion of two truncated transcription factors, and In wild-type fruit, RIN, a MADS-box transcription factor, is a key regulator of the ripening gene expression network, with hundreds of gene targets controlling changes in color, flavor, texture, and taste during tomato fruit ripening; , on the other hand, has low expression in fruit, and the potential functions of the fusion gene in ripening remain unclear. Here, overexpression of in transgenic wild-type cv Ailsa Craig tomato fruits impaired several ripening processes, and down-regulating expression in the mutant was found to stimulate the normal yellow mutant fruit to produce a weak red color, suggesting a distinct negative role for in tomato fruit ripening. By comparative transcriptome analysis of and:: RNA interference fruits, a total of 1,168 and 1,234 genes were identified as potential targets of RIN-MC activation and inhibition. Furthermore, the fusion gene was shown to be translated into a chimeric transcription factor that was localized to the nucleus and was capable of protein interactions with other MADS-box factors. These results indicated that tomato RIN-MC fusion plays a negative role in ripening and encodes a chimeric transcription factor that modulates the expression of many ripening genes, thereby contributing to the mutant phenotype.

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