Ethylene response factors ERF.B2 and ERF.B5 synergically regulate ascorbic acid biosynthesis at multiple sites in...

Area of Science:

• Plant Molecular Biology
• Plant Physiology
• Biochemistry

Background:

• Ascorbic acid (AsA) is vital for plant growth and acts as an antioxidant.
• While the AsA synthesis pathway is known, its regulation is not fully understood.
• AsA content is a key quality trait in tomatoes (Solanum lycopersicum).

Purpose of the Study:

• To identify and characterize novel regulators of AsA biosynthesis in tomato.
• To elucidate the molecular mechanisms controlling AsA production.
• To explore the potential of these regulators in enhancing plant stress tolerance.

Main Methods:

• Co-expression analysis to identify candidate regulators.
• Biochemical assays to confirm transcription factor binding to promoter regions.
• Gene overexpression and knockout studies to assess AsA levels.
• DNA affinity purification sequencing (DAP-seq) to identify target genes.
• Stress tolerance assays.

Main Results:

• SlERF.B2 and SlERF.B5 were identified as regulators co-expressed with SlGGP1, a key AsA biosynthesis gene.
• These ERFs bind to the SlGGP1 promoter and function as dimers to regulate its expression.
• Overexpression of SlERF.B2/SlERF.B5 significantly increased AsA levels (up to 149%), while knockout decreased them (up to 27%).
• SlERF.B2 was found to target promoters of SlGPI and SlDHAR1, indicating broader regulation of AsA biosynthesis.
• Overexpression enhanced reactive oxygen species scavenging and tolerance to oxidative and salt stress.

Conclusions:

• SlERF.B2 and SlERF.B5 are novel transcriptional regulators of AsA biosynthesis in tomato.
• A molecular network involving these ERFs controls AsA levels and impacts plant stress tolerance.
• This study provides a foundation for improving AsA content and stress resilience in crops.