A positive feedback loop mediated by CsERF31 initiates female cucumber flower development

Area of Science:

• Plant developmental biology
• Molecular genetics
• Ethylene signaling pathways

Background:

• Sex determination in plants like cucumber (Cucumis sativus L.) is crucial for adaptation and involves 1-aminocyclopropane-1-carboxylic acid synthases (CsACSs).
• The precise regulatory mechanisms governing CsACSs and their role in flower sex determination remain largely unknown.

Purpose of the Study:

• To elucidate the function of the gynoecium-specific gene ETHYLENE RESPONSE FACTOR31 (CsERF31) in cucumber female flower differentiation.
• To understand the molecular link between ethylene signaling and flower sex determination in cucumber.

Main Methods:

• Gene expression analysis
• Protein-DNA interaction assays
• RNA interference (RNAi) for gene knockdown
• Ectopic gene expression in transgenic plants

Main Results:

• Ethylene signaling activates CsERF31 via CsEIN3, which then stimulates CsACS2, creating a positive feedback loop for female flower development.
• Knockdown of CsERF31 resulted in the development of bisexual flowers instead of female flowers.
• Ectopic CsERF31 expression suppressed stamen development and promoted pistil development in male flowers, identifying CsERF31 as a sex switch.
• A similar regulatory mechanism was observed in melon (Cucumis melo L.).

Conclusions:

• CsERF31 acts as a molecular link between female-male and female-bisexual determination in cucumber.
• Ethylene signaling promotes female flower development by activating CsERF31, providing mechanistic insight into cucumber sex determination.