Metabolic Engineering of Wheat Provitamin A by Simultaneously Overexpressing <i>CrtB</i> and Silencing Carotenoid Hydroxylase (<i>TaHYD</i>)

Increasing the provitamin A content in staple crops via carotenoid metabolic engineering is one way to address vitamin A deficiency. In this work a combination of methods was applied to specifically increase β-carotene content in wheat by metabolic engineering. Endosperm-specific silencing of the carotenoid hydroxylase gene (<i>TaHYD</i>) increased β-carotene content 10.5-fold to 1.76 μg g^–1 in wheat endosperm. Overexpression of <i>CrtB</i> introduced an additional flux into wheat, accompanied by a β-carotene increase of 14.6-fold to 2.45 μg g^–1. When the “push strategy” (overexpressing <i>CrtB</i>) and “block strategy” (silencing <i>TaHYD</i>) were combined in wheat metabolic engineering, significant levels of β-carotene accumulation were obtained, corresponding to an increase of up to 31-fold to 5.06 μg g^–1. This is the first example of successful metabolic engineering to specifically improve β-carotene content in wheat endosperm through a combination of methods and demonstrates the potential of genetic engineering for specific nutritional enhancement of wheat