CRISPR-Cas9 is the most precise and efficient gene editing system that exists. Now, researchers working with golden rice are focused on developing a Cas9 system that can insert a desired gene, rather than simply delete or mutate an existing one. 

As part of their study, published in Nature Communications, they successfully inserted a carotenoid-production gene into the plant. Carotenoids are the orange pigments found in carrots, bell peppers, and other similarly colored plants. They also give golden rice its color.

The researchers first needed to find locations in the golden rice genome where an insertion does not change the plant’s growth and development. They looked for plants that had extra piece of DNA but a normal phenotype relative to a normal golden rice plant. They found a few good candidates and used one of them to create a guide RNA, which tells the Cas9 enzyme where to cut the plant's DNA and insert the desired gene.

The researchers confirmed that the desired carotene gene had indeed been inserted by sequencing the plant's genome and comparing it to to the unaltered golden rice genome. They found one line of plants that had the gene and produced more carotene than its wild type counterpart.

If used to insert other types of genes into food crops, this approach could go a long way toward producing drought-tolerant, pest-resistant, and eco-friendly plants.