Overexpression of the Watermelon Ethylene Response Factor ClERF069 in Transgenic Tomato Resulted in Delayed Fruit Ripening

ABSTRACT Watermelon fruit undergoes distinct development stages with dramatic changes during fruit ripening. To date, the molecular mechanics of watermelon ripening remain unclear. Genetic and transcriptome evidences suggested that the ethylene response factor (ERF) gene ClERF069 may be an important candidate factor affecting watermelon fruit ripening. To dissect the roles of ClERF069 in fruit ripening, structure and phylogenetic analysis were performed using the amplified full-length sequence. Normal-ripening watermelon 97103, non-ripening watermelon PI296341-FR and the RIL population were used to analyze ClERF069 expression dynamics and the correlation with fruit ripening indexs. The results indicated that ClERF069 belongs to ERF family group VI and show high homology (83% identity) to melon ERF069-like protein. ClERF069 expression in watermelon flesh was negatively correlated with fruit lycopene content and sugar content during fruit ripening progress. Further transgenic evidences indicated that overexpression of 35S:ClERF069 in tomato noticeably delayed the ripening process up to 5.2 days. Lycopene, β-carotenoid accumulation patterns were altered and ethylene production patterns in transgenic fruits was significantly delayed during fruit ripening. Taken together, watermelon ethylene response factor ClERF069 was concluded to be a negative regulator of fruit ripening.