Identification of key genes promoting stamen formation induced by silver nitrate in gynoecious melon

The gynoecious melon shows a high degree of hybrid seed production advantage, and exploitation of this property could improve both seed production and breeding, as well as reduce labor costs in melon production. The mechanism responsible the formation of hermaphroditic flowers by exogenous AgNO 3 spraying is unclear. In the present study, the gynoecious inbred melon line WI998 was treated with AgNO 3 solution to produce hermaphrodite flowers. Seedlings were investigated at the two, three, four, and five true‐leaf stages, and the AgNO 3 concentrations were 150, 300, 450, and 600 mg/L. We found that the optimum spray concentration of AgNO 3 was 450 mg/L with an optimum application time at the four true leave‐leaf stage. Transcriptome sequencing was performed on four‐true‐leaf stage samples sprayed with 450 mg/L AgNO 3 and water control to identify differentially expressed genes (DEGs). Twenty‐seven DEGs were identified and one, Cucumis melo epidermal pattern factor‐like protein 4 ( CmEPFL4 ), was involved in stamen development gene. Phenotypic analysis showed that CmEPFL4 played a key role in stamen induction, and heterologous expression of CmEPFL4 was found to interfere with stamen development and reduce the amount of pollen produced. Overall, the results demonstrated the importance of CmEPFL4 in AgNO 3 ‐induced hermaphroditic flower production and provide insight into AgNO 3 induction of stamen formation in the melon. A 450 mg/L silver nitrate was the optimal concentration for stamen induction of melon. Transcriptome sequencing identified a major differentially expressed gene Cucumis melo epidermal pattern factor‐like protein 4 ( CmEPFL4 ). The heterologous expression of CmEPFL4 in tomato lead to reduced pollen viability. The results was useful for revealing the mechanism of stamen induction in melon.