Submitted to: The Plant Cell
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/9/2004
Publication Date: 6/8/2004
Citation: Giovannoni, J.J. 2004. Genetic regulation of fruit development and ripening. The Plant Cell. 16:S170-180. Interpretive Summary: Fruit development and ripening is unique to plants and represents an important component of human and animal diets. Recent discoveries have shed light on the molecular basis of ripening control, suggest common regulators of ripening physiology at the DNA level among fruits from diverse species and have additionally defined new genes that regulate ripening. Specifically, analysis of fruit ripening mutants and ripening-related gene expression in tomato suggests the presence of "master-regulator" genes that control all aspects of ripening and downstream "specific- regulators" that control subsets of the ripening process (such as color development and production of flavor and aroma compounds). The role of light in fruit carotenoid accumulation is being examined and may represent a target for practical manipulation of fruit pigmentation and associated nutrient content. Continuing development of genomics tools for important fruit crops should foster accelerated discovery in fruit development and ripening research and a number of these resources are summarized with emphasis on tomato.
Technical Abstract: The LeMADS-RIN gene itself is induced at the onset of ripening without substantial influence by ethylene thus indicating higher order regulatory control. Comparative gene expression analysis in rin and nor fruit suggests an interesting sub-class of ethylene responsive genes, including E8, which respond to developmental signals and ethylene in rin but not nor fruit. E8 expression is induced to approximately 30% of maximal ripening levels in mature green rin fruit at a time consistent with the onset of ripening and attains normal expression in response to exogenous ethylene. The bi-modal regulation of E8 expression in rin and the absence of expression in nor, combined with the inability to induce ripening in either mutant via ethylene, defines a minimal regulatory network during ripening. In this network, ethylene regulates a subset of ripening genes either directly or in concert with developmental signals influenced by LeMADS-RIN and/or the nor gene product. E8 represents a regulatory motif in which nor but not LeMADS-RIN provides developmental control. In this instance, LeMADS-RIN impacts E8 gene expression mainly via activation of autocatalytic ethylene synthesis. Future characterization of ripening gene expression in nor will facilitate further definition of developmental regulation during ripening which is clearly impacted by both mutations in ways that do not overlap. The nor locus has been cloned and encodes a putative transcription factor with no relationship to MADS-box genes. The availability of this sequence should promote refinement of the developmental regulatory network governing fruit ripening.