A novel tomato F‐box protein, SlEBF3, is involved in tuning ethylene signaling during plant development and climacteric fruit ripening

Summary Ethylene is instrumental to climacteric fruit ripening and EIN 3 BINDING F‐ BOX ( EBF ) proteins have been assigned a central role in mediating ethylene responses by regulating EIN 3/ EIL degradation in Arabidopsis. However, the role and mode of action of tomato EBF s in ethylene‐dependent processes like fruit ripening remains unclear. Two novel EBF genes, Sl EBF 3 and Sl EBF 4 , were identified in the tomato genome, and Sl EBF 3 displayed a ripening‐associated expression pattern suggesting its potential involvement in controlling ethylene response during fruit ripening. Sl EBF 3 downregulated tomato lines failed to show obvious ripening‐related phenotypes likely due to functional redundancy among Sl EBF family members. By contrast, SlEBF3 overexpression lines exhibited pleiotropic ethylene‐related alterations, including inhibition of fruit ripening, attenuated triple‐response and delayed petal abscission. Yeast‐two‐hybrid system and bimolecular fluorescence complementation approaches indicated that Sl EBF 3 interacts with all known tomato Sl EIL proteins and, consistently, total Sl EIL protein levels were decreased in Sl EBF 3 overexpression fruits, supporting the idea that the reduced ethylene sensitivity and defects in fruit ripening are due to the Sl EBF 3‐mediated degradation of EIL proteins. Moreover, Sl EBF 3 expression is regulated by EIL 1 via a feedback loop, which supposes its role in tuning ethylene signaling and responses. Overall, the study reveals the role of a novel EBF tomato gene in climacteric ripening, thus providing a new target for modulating fleshy fruit ripening.