Mango Fructokinases Inhibit Sugar Accumulation and Enhance Energy Metabolism in Transgenic Tomato

Area of Science:

• Plant Biochemistry
• Fruit Quality Research
• Metabolic Engineering

Background:

• Mango fruit quality is significantly influenced by sugar content, which varies widely across cultivars.
• Preliminary evidence suggests that fructokinases (MiFRKs), specifically MiFRK1 and MiFRK2, play a role in regulating these intervarietal sugar differences.

Purpose of the Study:

• To characterize the function of MiFRK1 and MiFRK2 in mango sugar metabolism.
• To investigate the molecular mechanisms by which MiFRKs influence sugar accumulation and fruit quality.

Main Methods:

• Heterologous expression of MiFRK1 and MiFRK2 in tomato plants.
• Biochemical assays to determine fructose phosphorylation activity of MiFRK isoforms.
• Transcriptomic and metabolic analyses to assess the impact of MiFRK overexpression on gene expression and metabolite profiles.

Main Results:

• Both MiFRK1 and MiFRK2 phosphorylate fructose, promoting its catabolism. MiFRK2 from the low-sugar 'Renong No. 1' variety showed higher activity than that from the high-sugar 'Tainong No. 1' variety and MiFRK1.
• Overexpression of MiFRKs in tomato altered the expression of key genes involved in sucrose degradation (invertases), starch breakdown (β-amylases), and glycolysis (enolases), leading to reduced sugar accumulation.
• MiFRK1 and MiFRK2 demonstrated distinct regulatory effects on these metabolic pathways, indicating functional specialization.

Conclusions:

• MiFRKs are key regulators of sugar metabolism in mango, influencing sugar accumulation through modulation of central metabolic pathways.
• The differential activity and regulatory roles of MiFRK1 and MiFRK2 highlight their specialized functions in controlling sugar levels.
• MiFRKs represent promising targets for metabolic engineering strategies aimed at enhancing mango fruit quality by manipulating sugar content.