Abstract
Carotenoid content is a primary determinant of wheat nutritional value and affects its end-use quality. Wheat grains contain very low carotenoid levels and trace amounts of provitamin A content. In order to enrich the carotenoid content in wheat grains, the bacterial phytoene synthase gene (CrtB) and carotene desaturase gene (CrtI) were transformed into the common wheat cultivar Bobwhite. Expression of CrtB or CrtI alone slightly increased the carotenoid content in the grains of transgenic wheat, while co-expression of both genes resulted in a darker red/yellow grain phenotype, accompanied by a total carotenoid content increase of approximately 8-fold achieving 4.76 μg g(-1) of seed dry weight, a β-carotene increase of 65-fold to 3.21 μg g(-1) of seed dry weight, and a provitamin A content (sum of α-carotene, β-carotene, and β-cryptoxanthin) increase of 76-fold to 3.82 μg g(-1) of seed dry weight. The high provitamin A content in the transgenic wheat was stably inherited over four generations. Quantitative PCR analysis revealed that enhancement of provitamin A content in transgenic wheat was also a result of the highly coordinated regulation of endogenous carotenoid biosynthetic genes, suggesting a metabolic feedback regulation in the wheat carotenoid biosynthetic pathway. These transgenic wheat lines are not only valuable for breeding wheat varieties with nutritional benefits for human health but also for understanding the mechanism regulating carotenoid biosynthesis in wheat endosperm.
Highlights
Carotenoids are one of the most diverse classes of natural pigments produced by plants, algae, fungi, and bacteria, and have multiple functions because of their colour characteristics and antioxidant activities
Expression of CrtB or CrtI alone slightly increased the carotenoid content in the grains of transgenic wheat, while co-expression of both genes resulted in a darker red/yellow grain phenotype, accompanied by a total carotenoid content increase of approximately 8-fold achieving 4.76 μg g–1 of seed dry weight, a β-carotene increase of 65-fold to 3.21 μg g–1 of seed dry weight, and a provitamin A content increase of 76-fold to 3.82 μg g–1 of seed dry weight
The wheat cultivar Bobwhite was transformed with two carotenoid biosynthetic genes from bacteria, CrtB and CrtI, and the transgenic wheat showed significantly elevated provitamin A content
Summary
Carotenoids are one of the most diverse classes of natural pigments produced by plants, algae, fungi, and bacteria, and have multiple functions because of their colour characteristics and antioxidant activities. In plants, they guarantee the photosynthesis process by correcting assembly of the photosystems and scavenging reactive oxygen species derived from excess light energy. They guarantee the photosynthesis process by correcting assembly of the photosystems and scavenging reactive oxygen species derived from excess light energy They confer their colour in plant organs to attract pollinators and seed dispersers for plant reproduction. Consumption of carotenoids in the human diet is beneficial to health. Carotenoids are utilized as a healthcare food, food additives, and cosmetic colorants for their huge commercial value (Sandmann, 2001)
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