The effect of low ascorbic acid content on tomato fruit ripening

Area of Science:

• Plant Physiology
• Biochemistry
• Fruit Development

Background:

• Tomato fruit ripening involves significant cellular changes, including loss of firmness and pigment transformation.
• Oxidative stress metabolism, particularly the roles of ascorbic acid and hydrogen peroxide (H₂O₂), is crucial but not fully understood in fruit maturation.

Purpose of the Study:

• To investigate the specific roles of ascorbic acid and H₂O₂ in Solanum lycopersicum L. cv Micro-Tom fruit ripening.
• To analyze the impact of altered ascorbic acid levels on H₂O₂ production and ripening progression.

Main Methods:

• Utilized two GDP-L-galactose phosphorylase (GGP) mutants of Solanum lycopersicum L. cv Micro-Tom with reduced ascorbic acid content.
• Applied ascorbic acid and H₂O₂ treatments to wild-type and mutant plants.
• Analyzed fruit maturation phenotypes and quantified H₂O₂ levels.
• Localized reactive oxygen species (ROS) production using confocal microscopy.

Main Results:

• GGP mutants exhibited delayed ripening and lacked the typical H₂O₂ peak observed during maturation.
• Ascorbic acid supplementation accelerated ripening in mutants, restoring it to wild-type levels.
• Ascorbic acid treatment paradoxically increased H₂O₂ synthesis in mutants.
• Exogenous H₂O₂ delayed ripening in low-ascorbic acid mutants, indicating feedback regulation.
• ROS production was localized to chloroplasts across all genotypes.

Conclusions:

• The balance between ascorbic acid and H₂O₂ is a key regulator of tomato fruit ripening.
• Ascorbic acid influences H₂O₂ production, and both are essential for normal maturation.
• Chloroplasts are identified as a primary site of ROS generation during fruit ripening.