Spring in Japan is pink as cherry blossoms, but summer turns violet as the flowers of a climbing plant frequently grown in the gardens of the Rising Sun. It is a kind of morning glory, of the Ipomoea nil species, locally known as Asagao. This plant had its genome sequenced in 2016 and is now inaugurating the CRISPR era in floriculture.
At first sight, the experiment described in Scientific Reports seems simple enough. Kenta Watanabe from the University of Tsukuba and his colleagues used the plant bacterium Rhizobium as a vector to deliver the molecular scissors for genome editing into plant cells. They targeted a gene that is responsible for the flowers pigmentation (DFR-B), aiming to disrupt anthocyanin biosynthesis and change the color. The task was made harder by the risk of unwanted mutations, because of the near presence of two genes very closely related to the target (DFR-A and DFR-C). However the biotech tool did its job well, with high specificity, and as a result, 75% of the first generation of plants produced white rather than violet flowers. Quite a good percentage that envisages a bright future for CRISPR in the field of ornamental plants, for both basic and applied research.
The second generation inherited the induced mutation and also produced snow white flowers, even if some of them showed no sign of the introduced DNA. In short, the change introduced in the lab became indistinguishable from a natural mutation, and the edited plants cannot be considered transgenic, based on the product’s final characteristics. Therefore these whitened flowers could represent a litmus test for public perception of the most advanced biotech frontier and for the debate on how to regulate the commercialization of edited plants. Blue carnations modified by inserting foreign DNA through classic genetic engineering are already sold in Japan as fresh cut flowers. But morning glory is a plant holding a special place in the culture and iconography of the country, as well as in its scientific tradition. Japanese children learn to grow it at school, and the country geneticists have chosen it as a model plant for the study of flowering, collecting thousands of cultivars of different shapes and shades in the last century. The first blue specimens were imported from China in the eighth century AD, while the first artistic image representing spontaneous mutants characterized by white flowers dates back to 1631. The result is the same but nature took nearly 850 years to achieve what “has taken less than one using CRISPR”, according to a press release issued by researchers. They hope that the experiment will help the public to grasp the differences between spontaneous and induced mutations, and between old and new biotechnologies.
Photo credits: University of Tsukuba; Kyushu University; The National Diet Library Digital Collections.