In a world-first, Japanese scientists have used the CRISPR gene-editing tool to change the colour of ornamental morning glory flowers from violet to white by tweaking a single gene.
Japanese morning glory, or Asagao, was chosen for this study as it is one of two traditional horticultural model plants in the National BioResource Project in Japan (NBRP).
Extensive genetic studies of this plant have already been performed, its genome sequenced and DNA transfer methods established.
As public concern with genetic technologies such as CRISPR/Cas9 is currently a social issue in Japan, studies using this popular and widely-grown plant may help to educate the public on this topic, researchers said.
Researchers from the University of Tsukuba, the National Agriculture and Food Research Organization (NARO) and Yokohama City University in Japan targeted a single gene DFR-B, encoding an enzyme responsible for the colour of the plant's stems, leaves and flowers.
Two other very closely related genes (DFR-A and DRF-C) sit side-by-side, next to DFR-B. Therefore, the challenge was to specifically and accurately target the DFR-B gene without altering the other genes. The CRISPR/Cas9 system was used as it is currently the most precise method of gene editing.
The CRISPR/Cas9 system is based on a bacterial defense mechanism.
It is composed of two molecules that alter the DNA sequence. Cas9, an enzyme, cuts the two strands of DNA in a precise location so that DNA can be added or removed.
Cas9 is guided to the correct location by gRNA, or guide RNA, a small piece of RNA that has been designed to be complementary to the target DNA sequence.
Cas9 cuts the two strands of DNA at the target location, allowing DNA to be removed and/or added.
This technology is also extremely useful in confirming the function of genes.
The CRISPR/Cas9 system can be used to find out what an organism looks like after a known gene is disrupted, and confirms that the DFR-B gene is the main gene responsible for colour in Japanese morning glory plants.
Currently, CRISPR/Cas9 technology is not 100 per cent efficient, that is, not all targeted plants will be transgenic.
The mutation rate in the current study was 75 per cent, which is relatively high.
This is one of the reasons this research will greatly facilitate those interested in the modification of flower colours and shapes using the CRISPR/Cas9 system in ornamental flowers or vegetables.
The story of the Japanese morning glory started in the 8th century AD, with the introduction of wild blue-flowered plants into Japan from China.
In 1631, the first white-flowered Japanese morning glory was painted in Japan. What took nature nearly 850 years to achieve has taken less than one using the CRISPR/Cas9 system, indicating both its power and its potential.