A novel approach to carotenoid accumulation in rice callus by mimicking the cauliflower Orange mutation via genome editing

<jats:title>Abstract</jats:title> <jats:sec> <jats:title>Background</jats:title> <jats:p>β-carotene (provitamin A) is an important target for biofortification of crops as a potential solution to the problem of vitamin A deficiency that is prevalent in developing countries. A previous report showed that dominant expression of splicing variants in the <jats:italic>Orange</jats:italic> (<jats:italic>Or</jats:italic>) gene causes β-carotene accumulation in cauliflower curd. In this study, we focused on a putative orthologue of the cauliflower <jats:italic>or</jats:italic> gene in rice, <jats:italic>Osor</jats:italic>, and attempt to accumulate β-carotene in rice callus by modification of the <jats:italic>Osor</jats:italic> gene via genome editing using CRISPR/Cas9.</jats:p> </jats:sec> <jats:sec> <jats:title>Findings</jats:title> <jats:p>CRISPR/Cas9 vectors for the <jats:italic>Osor</jats:italic> gene were constructed and transformed into rice calli. Some transformed calli showed orange color due to β-carotene hyper-accumulation. Molecular analyses suggest that orange-colored calli are due to an abundance of in-frame aberrant <jats:italic>Osor</jats:italic> transcripts, whereas out-of-frame mutations were not associated with orange color.</jats:p> </jats:sec> <jats:sec> <jats:title>Conclusions</jats:title> <jats:p>We demonstrate that directed gene modification of the <jats:italic>Osor</jats:italic> gene via CRISPR/Cas9-mediated genome editing results in β-carotene fortification in rice calli. To date, golden rice, which accumulates β-carotene in rice endosperm, has been developed by conventional transgenic approaches. Our results suggest an alternative approach to enhancing β-carotene accumulation in crops.</jats:p> </jats:sec>