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.

西瓜果实经历了不同的发育阶段，在果实成熟期间发生了巨大变化。迄今为止，西瓜成熟的分子机理尚不清楚。遗传和转录组证据表明，乙烯反应因子（ERF）基因ClERF069可能是影响西瓜果实成熟的重要候选因子。为了分析ClERF069在果实成熟中的作用，使用扩增的全长序列进行了结构和系统发育分析。以正常熟西瓜97103，未熟西瓜PI296341-FR和RIL群体为材料，分析ClERF069的表达动态及其与果实成熟指数的相关性。结果表明ClERF069属于ERF族VI，与瓜类ERF069样蛋白显示出高度同源性（83％一致性）。西瓜果肉中ClERF069的表达与果实成熟过程中番茄红素含量和糖含量呈负相关。进一步的转基因证据表明，番茄中35S：ClERF069的过度表达将成熟过程明显延迟了5.2天。番茄红素，β-类胡萝卜素的积累方式发生了改变，并且在果实成熟期间，转基因果实中的乙烯产生方式明显延迟。两者合计，西瓜乙烯反应因子ClERF069被认为是果实成熟的负调节剂。