RALEIGH, N.C. – Over the last 10 years, gene editing has emerged as a useful tool in plant breeding and crop development. There are several different methods of gene editing, all with the same goal, to find and develop specific traits within the plant’s genome.
“In recent years, CRISPR/Cas9 technology has really brought genome editing to the fore, not only in plants sciences, but all aspects of biology,” said Ian Jepson, head of trait research and developmental biology at Syngenta’s Research Triangle Park, during a recent phone interview. “The technique, basically it is the ability to precisely modify parts of the genome.”
Genome editing is not the same as genetic modification. It works differently and only with genetic traits that are already present and possible within the plant’s DNA.
“If you introduce a CRISPR molecule in a cell, think about it as a targeted pair of scissors,” said Jepson. “It will go along the genome and it will cut that sequence in a very precise fashion.”
Cuts to the genome happen all the time naturally and randomly. There are mechanisms built into a cell’s nucleus to repair those cuts, the thing is that these mechanisms do not always put the DNA back together exactly as it was, mistakes get made.
“That could lead to two outputs, one is you can have an inactivation of a gene,” he said. “So, if you have a bad gene, you can essentially knock that out very precisely using this technique.”
The CRISPR molecule will cut the genome just ahead of the base pairs that code for the undesirable trait. When the cell puts the DNA back together, it can change those base pairs and that trait is no longer expressed.
Alternatively, when the DNA is repaired, desired traits that were not present or active before, could now be part of the genome.
It is important to note, gene edits are happening on at the embryonic stage, when the plant is still just one cell.
“The real step change with the CRISPR technique is efficiency,” he said. “Cost efficiency and precision is really quite dramatic and that really makes it a big advantage to plant breeding.”
Prior to gene editing, the process for developing a specific trait in a plant variety was through standard breeding methods. Crosses were made, seeds were planted, the resulting plants would be screened to find the desired trait.
This involved growing and screening hundreds of thousands of plants, looking for the few where the desired mutation and trait expression happened randomly.
“Today, we would probably only make 10 or 20 plants and we would have the beneficial mutation,” said Jepson. “Imagine the cost benefit of gene editing, you do not have to screen tens of thousands of plants in breeding programs to find the beneficial mutation.”
The plants grown would have all had the same CRISPR/Cas9 molecule introduced at the embryonic stage and all their DNA would have been cut in the same locations, significantly increasing the likely hood they express the desired trait or traits.
Multiple cuts or edits can be made through this technology at the same time, allowing for the development of multiple traits within the same plant. As opposed to multiple breeding programs, each cut is focused on a specific trait. Then the breeder crosses those programs to get the different traits in a single plant.
Gene editing is adding tremendous speed to the development of traits growers are looking for in their crops. These traits include drought tolerance, resistance to diseases and fungal infections, changing the fat content of soybean oil, and more.
Still, gene editing is not a replacement for genetic modification technology. It cannot create a genetic trait within a plant that is not already there to begin with.
Insect resistance is one example. There are no naturally occurring traits like the Bt corn trait that CRISPR technology could find and express.
These two technologies are not competing technologies. Quality seed varieties are being developed by using the two technologies, editing and modification, together, giving the grower a stronger crop.