Researchers generate tomatoes with enhanced antioxidant properties by genetic engineering

The School of Biological Sciences, Faculty of Science, the University of Hong Kong (HKU), in collaboration with the Institut de Biologie Moléculaire des Plantes (CNRS, Strasbourg, France), has identified a new strategy to simultaneously enhance health-promoting vitamin E by ~6-fold and double both provitamin A and lycopene contents in tomatoes, to significantly boost antioxidant properties.

The research group manipulated the plant isoprenoid pathway through the utilization of a variant of 3-hydroxy-3-methylglutaryl-coenzyme A synthase (HMGS). The overexpression of HMGS in tomatoes increased not only phytosterols, squalene, provitamin A and lycopene, but also vitamin E (α-tocopherol) by 494%.

The HMGS DNA used in these experiments originated from a food crop, Brassica juncea (Indian mustard). Earlier, this research group reported that the recombinant HMGS variant S359A (in which amino acid residue “serine” at position 359 was switched to “alanine”) exhibits 10-fold higher enzyme activity. The introduction of S359A in the model plant Arabidopsis increased phytosterol (phytosteroids, similar to cholesterol) content. Dietary phytosterols are important because they can lower blood cholesterol levels.

Now, the research group has introduced the S359A into tomatoes, a crop plant. Although there were no differences in the appearance and size of the transformed tomato fruits, total carotenoids including provitamin A and lycopene increased drastically by 169% and 111%, respectively.

Carotenoid extracts from S359A tomato fruits (right) with a deeper color contain more carotenoids (provitamin A and lycopene) than the control (left). S359A-1 and S359A-2 are two independent S359A tomato lines. © 2017 The Authors. Plant Biotechnology Journal published by Society for Exp. Biology and The Association of Applied Biologists and John Wiley & Sons Ltd.

Furthermore, these carotenoid extracts exhibited 89.5-96.5% higher antioxidant activity than the control. Besides carotenoids, the transformed tomatoes displayed elevations in vitamin E (α-tocopherol, 494%), squalene (210%), and phytosterols (94%). These observations were attributed to the increased expression of genes in the isoprenoid pathway.

Pan Liao et al. Improved fruit α-tocopherol, carotenoid, squalene and phytosterol contents through manipulation of Brassica juncea 3-HYDROXY-3-METHYLGLUTARYL-COA SYNTHASE1 in transgenic tomato, Plant Biotechnology Journal (2017). DOI: 10.1111/pbi.12828

Source: Phys.org

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