Genome editing could be an alternative approach to improve the vitamin A content of crops, according to a study by Akira Endo and colleagues at the National Agriculture and Food Research Organization and Ishikawa Prefectural University in Japan. The results of the study are published in Rice.

Beta-carotene, a precursor of vitamin A, is a vital target for biofortification of crops to aiming to address the problem of vitamin A deficiency prevalent in developing countries. In a previous study, it was reported that dominant expression of splicing variants in the Orange (Or) gene causes beta-carotene accumulation in cauliflower curd. In Endo and team's study, they focused on rice's Orange gene (Osor) and tested if they could increase the beta-carotene content of rice callus using CRISPR-Cas9. The transformed calli turned orange, indicating hyper-accumulation of beta-carotene. Molecular analyses indicated that orange-colored calli are caused by an abundance of in-frame aberrant Osor transcripts, while out-of-frame mutation was not associated with orange color.

Based on the findings, the researchers concluded that directed gene modification of Osor gene using CRISPR-Cas9-mediated genome editing leads to beta-carotene fortification in rice calli. This presents an alternative approach to improving beta-carotene accumulation in crops.

Read the research article in Rice.

Figure: Reproduction of carotenoid-accumulating phenotype of cauliflower Or mutation in rice callus.Target sequence in the Osor gene of each sgRNA for mimicking aberrant or transcripts expressed in the cauliflower Or mutation. Black and white boxes indicate exons and untranslated regions of the Osor gene, respectively. Sequences of exons are highlighted in gray; 20-nt target sequences are bold and underlined; 3-nt sequence indicating the protospacer adjacent motif (PAM) are boxed in red.