Gibberellins regulate masculinization through the SpGAI-SpSTM module in dioecious spinach

Area of Science:

• Plant biology
• Molecular genetics
• Reproductive biology

Background:

• Dioecious plant sex is primarily genetic but can be altered by environmental factors like phytohormones.
• Gibberellins (GAs) are known to influence flowering and sexual development, but their role in sex conversion in spinach is unclear.

Purpose of the Study:

• To elucidate the molecular pathway of gibberellin-induced sex conversion in dioecious spinach (Spinacia oleracea L.).
• To investigate the role of SpGAI and SpSTM in GA-mediated sex determination.

Main Methods:

• Application of GA3 to female spinach plants and assessment of sex conversion using molecular markers (T11A, SSR19).
• Gene silencing of SpGAI and SpSTM to observe effects on sex determination.
• Analysis of physical interactions between SpGAI and SpSTM.
• Investigation of SpSTM binding to the SpPI intron and its effect on SpPI expression.

Main Results:

• Exogenous GA3 application successfully induced complete masculinization in female spinach plants, resulting in functional stamens.
• Silencing of SpGAI, a DELLA repressor, mimicked the masculinization effect of GA.
• SpGAI physically interacts with the KNOX transcription factor SpSTM.
• Silencing SpSTM also led to female flower masculinization.
• SpSTM directly represses SpPI expression by binding to its intron.

Conclusions:

• GA induces female-to-male sex conversion in spinach via the SpGAI-SpSTM-SpPI regulatory module.
• This pathway clarifies the molecular mechanisms of sex determination and unisexual flower development in dioecious plants.