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

AbstractThe 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 AgNO3 spraying is unclear. In the present study, the gynoecious inbred melon line WI998 was treated with AgNO3 solution to produce hermaphrodite flowers. Seedlings were investigated at the two, three, four, and five true‐leaf stages, and the AgNO3 concentrations were 150, 300, 450, and 600 mg/L. We found that the optimum spray concentration of AgNO3 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 AgNO3 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 AgNO3‐induced hermaphroditic flower production and provide insight into AgNO3 induction of stamen formation in the melon.