Abstract
Fruit ripening is a complex developmental process responsible for the transformation of the seed-containing organ into a tissue attractive to seed dispersers and agricultural consumers. The coordinated regulation of the different biochemical pathways necessary to achieve this change receives considerable research attention. The MADS-box transcription factor RIPENING INHIBITOR (RIN) is an essential regulator of tomato (Solanum lycopersicum) fruit ripening but the exact mechanism by which it influences the expression of ripening-related genes remains unclear. Using a chromatin immunoprecipitation approach, we provide evidence that RIN interacts with the promoters of genes involved in the major pathways associated with observed and well-studied ripening phenotypes and phenomena, including the transcriptional control network involved in overall ripening regulation, ethylene biosynthesis, ethylene perception, downstream ethylene response, cell wall metabolism, and carotenoid biosynthesis. Furthermore, in the cases of ethylene and carotenoid biosynthesis, RIN interacts with the promoters of genes encoding rate-limiting activities. We also show that RIN recruitment to target loci is dependent on a normally functioning allele at the ripening-specific transcription factor COLORLESS NONRIPENING gene locus, further clarifying the relationship between these two ripening regulators.
Highlights
Fruit ripening is a complex developmental process responsible for the transformation of the seed-containing organ into a tissue attractive to seed dispersers and agricultural consumers
RIPENING INHIBITOR (RIN) antibodies recognize a 28-kD band in the wild-type (Ac) fruit extract but not in the rin mutant extract. This size corresponds to the expected Mr of the RIN protein. The fact that this band is not detected in rin mutant protein extract but is present in the isogenic rin 35S:: RIN line confirms that it corresponds to the RIN protein
As described previously (Vrebalov et al, 2002), the rin mutation is caused by a genomic deletion removing the 3#-untranslated region encoding exon of the RIN gene creating a translational fusion with the adjacent MACROCALYX (MC) MADS-box gene
Summary
Fruit ripening is a complex developmental process responsible for the transformation of the seed-containing organ into a tissue attractive to seed dispersers and agricultural consumers. The MADS-box transcription factor RIPENING INHIBITOR (RIN) is an essential regulator of tomato (Solanum lycopersicum) fruit ripening but the exact mechanism by which it influences the expression of ripening-related genes remains unclear. Using a chromatin immunoprecipitation approach, we provide evidence that RIN interacts with the promoters of genes involved in the major pathways associated with observed and well-studied ripening phenotypes and phenomena, including the transcriptional control network involved in overall ripening regulation, ethylene biosynthesis, ethylene perception, downstream ethylene response, cell wall metabolism, and carotenoid biosynthesis. The exact physiological and chemical changes associated with fruit ripening differ among species, some general changes are characteristic of many These include modification of tissue firmness and cell wall structure, changes in sugar/starch metabolism, alteration of composition and levels of secondary metabolites such as pigments, and increased susceptibility to pathogens (Seymour, 1993). The exact mechanism by which RIN regulates the expression of genes involved in the different aspects of fruit ripening has only begun to be addressed. Ito et al (2008) have shown that RIN can bind to CArG box primers in vitro and Fujisawa et al (2011) confirmed RIN’s binding to ethylene synthesis and cell wall metabolism genes, the promoters of which contain CArG box sequences
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