AcWRKY70-AcAMR1 modulates ascorbic acid accumulation in kiwifruit

Area of Science:

• Plant Molecular Biology
• Fruit Biochemistry
• Agricultural Science

Background:

• Kiwifruit (Actinidia species) are a significant source of ascorbic acid (AsA), but AsA content varies greatly among cultivars.
• The genetic regulation of these variations in AsA accumulation in kiwifruit remains poorly understood.
• Identifying key regulatory genes is crucial for improving fruit nutritional quality.

Purpose of the Study:

• To investigate the molecular mechanisms controlling ascorbic acid (AsA) biosynthesis and accumulation in kiwifruit.
• To identify and characterize novel genes involved in regulating AsA levels in kiwifruit cultivars.
• To explore the regulatory network governing AsA content for potential breeding applications.

Main Methods:

• Cloning of AsA negative regulators (AeAMR1 and AcAMR1) from Actinidia eriantha and Actinidia chinensis.
• Gene expression analysis, gene overexpression, and gene silencing to assess the impact on AsA content.
• Promoter analysis, Yeast one-hybrid (Y1H) screening, Electrophoretic Mobility Shift Assay (EMSA), GUS, and dual-luciferase assays to elucidate regulatory interactions.

Main Results:

• AcAMR1 negatively regulates AsA content in kiwifruit, with higher expression in 'Hongyang' correlating to lower AsA levels.
• Significant differences in promoter regions of AeAMR1 and AcAMR1 were observed, indicating distinct regulatory elements.
• AcWRKY70 was identified as a direct upstream regulator that binds to the AcAMR1 promoter and represses its activity, thereby positively influencing AsA levels.

Conclusions:

• A novel AcWRKY70-AcAMR1 regulatory module controlling AsA biosynthesis in kiwifruit has been defined.
• This pathway provides critical insights into the genetic basis of AsA variation in kiwifruit.
• The identified genes and regulatory interactions serve as valuable genetic targets for breeding AsA-enriched kiwifruit cultivars.