Seed specific overexpression of a modified wheat Or gene leads to enhanced β-carotene in rice and wheat grains

Abstract

Vitamin A deficiency is a major public health problem affecting up to 50% of the worlds population, as either wheat or rice, which are poor in many essential micronutrients such as vitamin A, are major staple food crops. Biofortification of cereal crops with {beta}-carotene (provitamin A) through genetic engineering is a potential solution to overcome vitamin A deficiency. The Orange (Or) protein is involved in the regulation of carotenoid accumulation and previous studies demonstrated high carotenoid accumulation due to a single-nucleotide polymorphism (SNP) in the CDS leading to substitution of Arg to His in the OR protein results in carotenoid accumulation. In the present study, we showed that this substitution of a single amino acid at position 110 (Arg to His) of wild-type wheat TaOr (referred to as TaOrHis110) increased {beta}-carotene accumulation in transgenic wheat and rice plants overexpressing TaOrHis110 under the control of the seed-specific promoter Glu-1D1. HPLC analysis revealed increase in {beta}-carotene content in rice grain up to 8-fold in case of TP309 (japonica) cultivar, 13-fold in case of IET10364 (indica) cultivar and 7-fold in wheat cv. CPAN1676. Additionally, most of the carotenoid biosynthetic pathway genes were found to be upregulated in TaOrHis110 overexpressing seeds of TP309 and IET10364, which positively correlated with maximum increase in {beta}-carotene content.