Expressing CaCCS encoding capsanthin/capsorubin synthase in tomato increases fruit provitamin A content and yield

Area of Science:

• Plant Biotechnology
• Metabolic Engineering
• Nutritional Science

Background:

• Carotenoids, including beta-carotene (provitamin A), are vital plant pigments with health benefits.
• Biofortification strategies aim to enhance the nutritional content of staple crops.
• Pepper-specific ketocarotenoids, capsanthin and capsorubin, are potent antioxidants.

Purpose of the Study:

• To investigate the role of Capsanthin/capsorubin synthase (CaCCS) in carotenoid biosynthesis.
• To engineer tomato (Solanum lycopersicum) for enhanced accumulation of beta-carotene and ketocarotenoids.
• To assess the potential of CaCCS for improving tomato nutritional profiles and yield.

Main Methods:

• Virus-induced gene silencing of CaCCS in pepper (Capsicum annuum).
• Bacterial carotenogenic system to compare CaCCS and tomato lycopene beta-cyclase (LCYB) activity.
• Constitutive expression of CaCCS in wild-type and mutant tomato lines ('Micro-Tom' WT and pyp1-1).
• Controlled crosses to introduce CaCCS into selected tomato inbreds for hybrid development.

Main Results:

• CaCCS silencing in pepper reduced beta-carotene synthesis and altered carotenoid profiles.
• CaCCS demonstrated superior lycopene cyclization and unique capsanthin synthesis in bacteria.
• CaCCS-overexpressing tomatoes showed increased capsanthin, capsorubin, beta-carotene, and xanthophyll esters.
• CaCCS expression boosted fruit yield, volatiles, amino acids, phenolics, and ascorbic acid, while reducing sugars.
• CaCCS-derived tomato hybrids met provitamin A dietary recommendations with moderate consumption.

Conclusions:

• CaCCS is a key enzyme for both lycopene cyclization and ketocarotenoid biosynthesis.
• CaCCS overexpression is a potent strategy for biofortifying tomatoes with provitamin A and other beneficial compounds.
• Xanthophyll esterification appears to facilitate overall carotenoid accumulation in tomato fruits.
• Engineered tomatoes offer a viable approach to combat provitamin A deficiency and enhance dietary phytochemical intake.