Plant transformation is a scientific approach whereby DNA from any organism is inserted into the genome of a species of interest. The inserted DNA is called a “transgene”, and the resulting plant is said to be “transgenic”.
Transgenic plants are vital for both research and agriculture. They help the plant research community test hypotheses, greatly expanding our understanding of plant biology. Transgenic technology may also improve key characteristics of economically important crops, thereby helping both growers and consumers. These traits include yield, disease resistance, abiotic stress tolerance, and nutrient abundance among others. When a transgene safely improves one of these traits in an economically important crop and is approved for use by the United States Department of Agriculture (USDA), the U.S. Food and Drug Administration (FDA), and the Environmental Protection Agency (EPA), the plants may then move from the lab to farmers’ fields and the tables of consumers.
In the past, plant researchers, other than those working with the moss Physcomitrella patens, have been disadvantaged by the near inability to perform targeted gene modifications. Recent advances, however, have led to three gene editing technologies that can be applied to plants: zinc finger nucleases (ZFNs), transcription activator-like effector nucleases (TALENs), and clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9), also known as the CRISPR/Cas9 system. These technologies now enable plant scientists to make targeted deletions, point mutations, and so on.
Of the three new gene-editing technologies, the CRISPR/Cas9 system is the most easily adapted to new targets and new mutations, and it can be applied in three different ways. In the first, the components of the CRISPR/Cas9 system are transformed into plants, plants with the desired mutations are selected, and the transgene(s) is outcrossed so that the final mutated line has the desired mutation but not the transgene(s). The other two methods do not include a transgenic intermediate and utilize plant protoplasts. In the second method, purified Cas9 protein and the required targeting RNAs are transfected into protoplasts, and then whole plants are grown from the gene-edited cells. In the third approach, the components of the CRISPR/Cas9 system are transiently expressed in the cells, and then whole plants are grown from the gene-edited cells.