Can you modify a plant’s genetics without creating a GMO? A new research paper published in Nature Biotechnology claims new CRISPR-Cas9 technology can genetically alter a plant without creating a GMO – in our current understanding of what that is.
Scientists at South Korea’s Institute for Basic Science (IBS) Center for Genome Engineering say that their new technique, explained in the published paper ‘DNA-free genome editing in plants with preassembled CRISPR-Cas9 ribonucleoproteins‘ doesn’t introduce any foreign DNA, so that the plants that are created aren’t caught up in what most people fear and oppose about GMOs.
But is it really different enough? What’s this CRISPR-Cas9 technique and how is it different?
Let’s dig a little deeper to understand what’s going on here. Fortunately GardenDrum can more simply explain the science gobbledy-gook by calling on Alison Stewart, GardenDrum author and freelance science journalist specialising in genetics!
There’s one bit of basic biology you need to understand it all, and that is that “DNA makes RNA makes protein”. In cells, the information encoded by a DNA sequence is used firstly to direct the production of a corresponding sequence of RNA. Most RNAs in turn direct the production of specific proteins but some RNAs have their own functions in the cell.
CRISPR-Cas9 is a way of introducing a targeted change/mutation into a specific DNA sequence. It is based on a strategy used by some bacteria to identify and disable invading viruses. The “CRISPR” bit is a piece of RNA that has two sections: one section has a sequence that allows it to identify and bind to the target DNA that you want to edit, and the other section forms a structure that allows a specific protein, the Cas9 protein, to recognise the RNA-DNA complex, unwind the DNA at the target site and then cut both of its strands. There are various different ways that the cell will then try to repair the broken DNA and you can set things up so that the repair will happen in a specific way so that you end up with an “edited” piece of DNA that has a directed change in its sequence.
Normally, the first step in the CRISPR-Cas9 system is to make a piece of DNA that codes for both the specific version of CRISPR RNA that you need (ie one which will recognise the target DNA sequence that you want to edit) and the Cas9 protein. You get this DNA into the nucleus of the target cells (I’m glossing over some technical stuff about how you get it in there!) and then the cells’ own machinery for making RNAs and proteins uses the information in the introduced DNA to synthesise both the CRISPR RNA and the Cas9 protein. They then get to work and do the editing job.
What the Korean group have done is to work out a way to use the CRISPR-Cas9 system that doesn’t involve introducing “foreign” DNA into the plant cells. Instead of putting a piece of DNA that codes for CRISPR and Cas9 into the plant cells, and letting the cells make the CRISPR RNA and Cas9, they have short-circuited things by making the CRISPR RNA and the Cas9 protein in the test tube and introducing them into the cells as an RNA-protein complex, also called a ribonucleoprotein.
They say that if the definition of a GMO is an organism that has been engineered by the introduction of foreign DNA, then plants modified by their method are not “GMOs”. Whether this distinction would satisfy opponents of GMOs remains to be seen. I rather doubt it.
The rest of their paper is about showing that their process is efficient, that you don’t get lots of unwanted changes in the DNA, and that the targeted change is stable, so that you can grow up whole plants whose cells all carry the same directed DNA sequence change. Apparently the CRISPR-Cas9 system is also cheap, which would obviously make it attractive to agribusiness.
The first step is introducing a DNA that codes for both the CRISPR RNA and the Cas9 protein. That’s the bit you need in order to understand how the Korean method differs.
[More at Asian Scientist]