Location: Plant, Soil and Nutrition ResearchTitle: A tomato (Solanum lycopersicum) APETALA2/ERF gene, SlAP2a, is a negative regulator of fruit ripening Author
Submitted to: Plant Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/3/2010
Publication Date: 10/18/2010
Citation: Chung, M., Vrebalov, J., Alba, R., Lee, J., Mcquinn, R., Klein, P., Giovannoni, J.J. 2010. A tomato (Solanum lycopersicum) APETALA2/ERF gene, SlAP2a, is a negative regulator of fruit ripening. Plant Journal. 64:936-947. Interpretive Summary: Fruit ripening is a developmental and biochemical process that involves numerous different metabolic changes and has evolved as a mechanism of seed dispersal. In the case of fleshy fruits the changes in color, texture, flavor, aroma and nutritional characteristics not only make fruit attractive for seed dispersal organisms, but also provides essential vitamins, minerals, phytonutrients, fiber and additional beneficial compounds for human diets and animal feed. From the nutritional perspective, tomato serves as a model for fruit ripening and more specifically for regulation of pathways impacting important nutritive compounds such as carotenoids (e.gs. lycopene, ß-carotene) and vitamins (e.gs. ascorbate, folate, tocopherols) which play important roles in the prevention of diseases and promotion of health. Here we report functional characterization of a tomato AP2 gene originally defined through our transcriptional profiling studies as being associated with fruit development. We demonstrate that this gene plays a critical role in fruit ripening, but not in other aspects of floral development.
Technical Abstract: The transition of fleshy fruit maturation to ripening is regulated by exogenous and endogenous signals which coordinate the transition of the fruit to a final state of attractiveness to seed dispersing organisms. Tomato is a model for biology and genetics regulating specific ripening pathways including ethylene, carotenoids and cell wall metabolism in addition to upstream signaling and transcriptional regulators. Ripening associated transcription factors described to date including the RIN-MADS, CLEAR NON-RIPENING, TAGL1 and LeHB-1 genes all encode positive regulators of ripening phenomena. Here we describe an APETALA2 transcription factor (SlAP2a) identified through transcriptional profiling of fruit maturation that is induced during and which negatively regulates tomato fruit ripening. RNAi repression of SlAP2a results in fruits which over-produce ethylene, ripen early and modify carotenoid accumulation profiles by altering carotenoid pathway flux. These results suggest that SlAP2a functions during normal tomato fruit ripening as a modulator of ripening activity that acts to balance the activities of positive ripening regulation and shifts fruit carotenoid pigmentation in the direction of predominant lycopene (red) from beta-carotene (orange) accumulation.