Submitted to: Journal of Experimental Botany
Publication Type: Peer reviewed journal
Publication Acceptance Date: 6/7/2010
Publication Date: 9/15/2010
Citation: Elitzur, T., Vrebalov, J., Giovannoni, J.J., Ocampo, E., Goldschmidt, E., Friedman, H. 2010. The regulation of MADS-box gene expression during ripening of banana and their regulatory interation with ethylene. Journal of Experimental Botany. 61:1523-1535. Interpretive Summary: Fruit ripening is a genetically controlled program that requires the coordination of fruit softening, color change, aroma development, sugar accumulation and reduction in acid levels. This program requires the control of developmental components, and in climacteric fruit also components of the ethylene synthesis and ethylene response pathways. Recently, facilitated by the cloning of the genes mutated in several spontaneous tomato mutations inhibited in ripening, several components of the singling mechanisms of the developmental pathway have been discovered. A cascade of transcription regulators acting upstream of the ethylene pathway has been revealed, and MADS-box genes play a major role in the molecular circuit of developmental regulation. Banana like tomato is a climacteric fruit, which is characterized by an increase in respiration and a burst in ethylene production occurring at the onset of ripening. However, in light of the fact that banana is a monocot, it is still not clear if this fruit uses similar component to those of the tomato eudicot for controlling ripening. In this study we have cloned a full length of six MADS-box genes from banana (Grand Nain), examined the ability of two of these genes to complement rin mutation in tomato and study their expression patterns in the various banana organs and during ripening in peel and pulp. Our data suggest that some of these MADS-box genes are candidates for regulators of banana ripening.
Technical Abstract: MADS-box genes (MaMADS1-6), potential components of the developmental control of ripening have been cloned from Grand Nain banana cultivar. Similarity of these genes to tomato LeRIN is very low and neither MaMADS2 nor MaMADS1 complement the tomato rin mutation. Nevertheless, the expression patterns specifically in fruit and the induction during ripening and in response to ethylene and 1-MCP, suggest that some of these genes serve as regulators of ripening. MaMADS1, 2 and 3 are highly expressed specifically in fruit, while the others are expressed in fruit as well as in other organs. Moreover, the pulp and peel differ in the suit of MaMADS-box genes expressed during ripening. In the pulp, the increase in MaMADS2, 4, 5 expression and to a lesser degree also MaMADS3, preceded increase in ethylene production, but coincides with CO2 peak. In the peel, however, the increase in expression of MaMADS1, 3 and to a lesser degree also of MaMADS4 coincided with increase in ethylene production. Except MaMADS3, which was induced by ethylene in pulp and peel, only MaMADS4, 5 in pulp and MaMADS1 in peel were induced by ethylene. Only MaMADS2 is neither induced by ethylene nor by 1-MCP, and it is expressed mainly in pulp. Our results suggest that two independent ripening programs are employed in pulp and peel which involved the activation of mainly MaMADS2, 4 and 5 in pulp and mainly MaMADS1, and 3 in peel.