Scientists have developed a single-step gene editing process that can increase corn yields. The new technique uses pollen to transfer the components of CRISPR-Cas9 into another plant allowing them to produce gene edited corn, a process previously hindered by the thick cell walls of many plants, such as corn and wheat. Results of the first set of experiments appeared on 4 March in Nature Biotechnology (1).
Gene editing is an important tool used by researchers in many areas of biology. However, several crop varieties, including staple crops like wheat and corn, are resistant to gene editing. While CRISPR–Cas9 works efficiently in plant cells, unlike animals and other plant species, these crops have a much thicker cell wall making it incredibly difficult to actually use the technique.
So, the researchers had to get creative with their approach. The team of scientists, led by Dr Timothy Kelliher and Dr Qiudeng Que from Syngenta, a global agriculture company, overcame this problem by combining two technologies: haploid induction and genome editing.
Haploid induction is a phenomenon that occurs when pollen triggers the development of a gamete into a plant without fertilisation. The newly produced plant only contains one set of chromosomes and is therefore haploid instead of diploid. Corn or maize is normally diploid, but plants with a mutation in the MATRILINEAL gene produce the so-called inducer pollen that can trigger the haploid induction process.
The technique has become an important tool in maize breeding over the past 10 years ― even without gene editing, haploid induction enables more efficient crop production and therefore higher yields. But in this case, the effects can be enhanced even further by using pollen to carry the CRISPR toolkit from one genetically modified plant into the cells of another plant, thus realising “one-step genome editing”.
Initial experiments successfully produced corn varieties with larger kernels, and thus, higher yields. Although, thus far, the process has only been demonstrated in the laboratory.
While the researchers focused on developing plants with higher yields, gene editing has the potential to generate other desirable traits, such as pest resistance, thereby reducing the need for pesticides and other chemicals that are harmful to both the environment and human health. Moreover, drought-resistant crops could be more robust in the face of the growing threat posed by climate change.
Technologies like this are becoming increasingly important, particularly, as the global trend toward a few high-value crop varieties continues to threaten sustainable agriculture ― increasing the need for more robust crop species. The researchers are hoping to expand this technology to other crops like wheat, cabbage, broccoli, kale, and cauliflower.
Based on this new technique, genetically modified plants could potentially be used to spread desirable traits to the other plants via pollination without permanently editing them since only the pollinated plant is affected but not its offspring. Since the CRISPR genes are not permanently put into the DNA of the resulting crops, the resulting plants are unlikely to be classified as genetically modified.
(1) Kelliher, T. et al. One-step genome editing of elite crop germplasm during haploid induction. Nature Biotechnology (2019). DOI: 10.1038/s41587-019-0038-x