Submitted to: Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/2/2002
Publication Date: 4/1/2002
Citation: VREBALOV, J., RUEZINSKY, D., PADMANABHAN, V., WHITE, R.A., MEDRANO, D., DRAKE, R., SCHUCH, W., GIOVANNONI, J.J. A MADS-BOX GENE NECESSARY FOR FRUIT RIPENING AT THE RIPENING-INHIBITOR (RIN) LOCUS. SCIENCE. 2002. V. 296. P. 343-346. Interpretive Summary: The rin mutant exhibits general ethylene sensitivity including the seedling triple response, floral abscission and petal and leaf senescence. Nevertheless, rin fruit do not ripen in response to exogenously supplied ethylene but do display up-regulation of at least some ethylene-inducible genes, indicating they retain ethylene sensitivity. We and others have interpreted these results to mean that the RIN gene encodes a genetic regulatory component necessary to trigger climacteric respiration and ripening-related ethylene biosynthesis, in addition to requisite factors whose regulation is outside the sphere of ethylene's influence. As such, the RIN gene product acts upstream of both ethylene and non-ethylene mediated ripening control, and thus may also represent a regulatory mechanism shared among climacteric and non-climacteric species. We previously reported mapping of the rin locus at high resolution to tomato chromosome 5. Here we report positional cloning and functional characterization of two MADS-box genes at the rin locus. MADS-box genes encode transcription factors that in plants are primarily involved in floral development but have never before been demonstrated to regulate fruit ripening.
Technical Abstract: Tomato plants harboring the ripening-inhibitor (rin) mutation yield fruits that fail to ripen. Additionally, rin plants display enlarged sepals and loss of inflorescence determinacy. Positional cloning of the rin locus revealed two tandem MADS-box genes (LeMADS-RIN, LeMADS-MC) whose expression patterns suggested roles in fruit ripening and sepal development, respectively. The rin mutation alters expression of both genes. Gene repression and mutant complementation demonstrate that LeMADS-RIN regulates ripening while LeMADS-MC impacts sepal development and inflorescence determinacy. LeMADS-RIN demonstrates a novel and agriculturally important function of plants MADS-box genes and additionally provides the first molecular insight into non-hormonal (developmental) regulation of ripening.