SlMYB99-mediated auxin and abscisic acid antagonistically regulate ascorbic acids biosynthesis in tomato

Area of Science:

• Plant Biology
• Biochemistry
• Molecular Genetics

Background:

• Ascorbic acid (AsA) is a vital water-soluble antioxidant in plants and humans.
• Understanding AsA biosynthesis regulation is key for developing crops with enhanced nutritional value.
• Phytohormones play critical roles in plant development and stress responses.

Purpose of the Study:

• To elucidate the regulatory mechanism of ascorbic acid (AsA) biosynthesis in tomato.
• To identify key genes and protein interactions involved in AsA accumulation.
• To understand the role of phytohormones, specifically auxin and abscisic acid, in modulating AsA levels.

Main Methods:

• Investigated transcriptional regulation by SlARF4 and SlMYB99.
• Analyzed the role of SlMAPK8 in phosphorylating and activating SlMYB99.
• Examined protein-protein interactions between SlMYB99 and SlMYB11.
• Studied the impact of auxin and abscisic acid on AsA biosynthesis genes (GPP, GLDH, DHAR).

Main Results:

• SlARF4 transcriptionally inhibits SlMYB99, which activates AsA biosynthesis genes.
• SlMAPK8 phosphorylates and enhances SlMYB99 activity.
• SlMYB99 and SlMYB11 interact to synergistically upregulate AsA synthesis genes.
• Auxin and abscisic acid antagonistically regulate AsA biosynthesis via the SlMAPK8-SlARF4-SlMYB99/11 pathway.

Conclusions:

• A novel auxin/abscisic acid-dependent regulatory module (SlMAPK8-SlARF4-SlMYB99/11) controls AsA biosynthesis in tomato.
• This pathway is crucial for AsA accumulation during plant development and drought tolerance.
• Findings provide insights for breeding tomatoes with higher AsA content.