An ACC Oxidase Gene Essential for Cucumber Carpel Development

Area of Science:

• Plant biology
• Genetics
• Biochemistry

Background:

• Plant sex determination is crucial for genetic diversity, with ethylene regulating flower development in cucumber and melon.
• Key genes identified include ACC synthases and the CmWIP1 transcription factor, a negative regulator of femaleness.

Purpose of the Study:

• To identify the critical ACC oxidase (ACO) gene in cucumber sex determination.
• To elucidate the mechanism by which CmWIP1 represses female flower development.

Main Methods:

• Investigated the role of CsACO2 in cucumber androecy through mutation analysis.
• Analyzed CsACO2 expression patterns in relation to female flower development and ethylene biosynthesis.
• Examined the interaction between CsWIP1 and the CsACO2 promoter.

Main Results:

• A mutation in CsACO2 resulted in male-only flowers (androecy) due to disrupted enzymatic activity and reduced ethylene emission.
• CsACO2 expression in carpel primordia overlapped with CsACS11, suggesting a role in providing ethylene for female flower development.
• The orthologous CmACO3 in melon showed a similar expression pattern, indicating conserved function.
• CsWIP1 directly repressed CsACO2 expression, identifying a regulatory interaction.

Conclusions:

• A conserved regulatory module involving WIP1 transcription factors and ACO enzymes controls unisexual flower development in cucumber and melon.
• CsACO2 is a critical gene for female flower development in cucumber.
• WIP1 acts as a negative regulator of femaleness by repressing ACO gene expression.