Does This Change Everything? – A New “Toolkit” For Precise Gene Editing In Plants

Public Domain

Public Domain

Double helix in the sky tonight
Throw out the hardware
Let’s do it right
” – Steely Dan

Here A CRISPR, There A CRISPR, Everywhere A CRISPR, CRISPR….

Yikes! You can hardly go through a week these days without reading some headline with “CRISPR” in the title. (Even in Time magazine!)

Yes, “CRISPR” currently is (and has been for about the past year or so) a pretty big deal in the popular press. (In mainstream scientific journals, such as Nature and Science, it’s been a big deal since about 2013.)

Why?

Well, because CRISPR, or more precisely the CRISPR/Cas9 system, is a powerful new way to edit DNA.

If you’re unfamiliar with CRISPR, here’s a nice YouTube video (from my old home town, btw) that I think does a pretty good job explaining it.

Nota bene: This is an excellent example of how a basic research project can lead to a major technological advance and of why it’s so critically important to support basic research (a.k.a., fundamental or pure research), in addition to “applied” research.

OK, so molecular biologists now have a new “toolkit” for tinkering with the genomes of biological organisms.

But why do many plant scientists say that CRISPR may “change everything” when it comes to the realm of plant genetic engineering and, ultimately, the fundamental nature of plant “GMO’s”?

Please allow me to explain….

Using a “Scalpel” Instead of a “Shotgun”

Up until recently, most plant GMOs have pretty much been the result of a “shotgun” approach to plant genetic engineering.

That is, using Agrobacterium or a “gene gun” to deliver foreign genes into plant cells, these genes were randomly inserted into the plant genome, sometimes multiple times, in several different locations within the genome.

“In addition, and due to the random transfer process, insertion may disrupt a resident gene and, accordingly, bring on unwanted phenotypic side-effects.”

“From 2006 to 2012, a few crop plants were successfully and precisely modified using zinc-finger nucleases. A third wave of improvement in genome editing, which led to a dramatic decrease in off-target events, was achieved in 2009-2011 with the TALEN technology.”

“…zinc-finger and TALEN nucleases, were based on specific polypeptide-to-DNA binding which is tedious to optimize; CRISPR-Cas9 is based on DNA-RNA hybridization which is well mastered. CRISPR-Cas9 nowadays appears as the most efficient system to achieve site-specific genome editing–easiest, more reliable and cheapest as well.” (From: Quetier below)

With CRISPR/Cas9, plant genetic engineers now have the ability to relatively easily and precisely “edit” the plant genome, that is, with a molecular “scalpel” instead of a “shotgun”.

Are CRISPR-modified plants GMOs?

What’s especially important to the whole anti-GMO debate is that researchers have recently devised a way to use CRISPR to precisely modify a plant’s genome without introducing any foreign DNA. (See Cyranoski below)

This whole issue has been nicely summarized by Dr. Johannes Fütterer, a Senior researcher at the Institute of Agricultural Sciences, ETH Zurich, in an article entitled The future of plant breeding”:
“The special feature of CRISPR/Cas is that the modifications produced in the genome do not differ from naturally occurring mutations in plants and animals caused by environmental influences on the genome, such as natural radioactive radiation, reactive metabolites or even by defects in DNA replication and inheritance. Random mutagenesis by chemical treatment or irradiation has been used in mutation breeding for many years and contributed to major yield gains in our crops in the 20th century. Worldwide this type of mutation breeding led to currently more than 3088 varieties from 190 species.
As plants modified with CRISPR/Cas cannot be distinguished from those modified with conventional breeding techniques, the question arises: if a new breeding method triggers a targeted modification in the genome of the given species that can also be achieved through conventional breeding – admittedly with significantly greater effort – or accidental mutation, should the resulting product be regarded as a GMO (genetically modified organism) or not? The current debate focuses accordingly on whether a regulation should be process- or product-related.

And what’s amazing is that some have suggested that this new “toolkit” for precise gene editing in plants is compatible with organic farming, since it will facilitate the “rewilding” of crop plants. (See Andersen et al below)

I’m skeptical that organic farmers would accept crop plants genetically modified using these “new breeding techniques”. But these are early days for CRISPR/Cas 9, and it’s possible that this new technology may eventually overcome zealotry.

Online Resources

  • On the usefulness of CRISPR for exploring how genomes work: CRISPR: gene editing is just the beginning
  • Are CRISPR-modified plants GMOs? :

    “GREEN LIGHT IN THE TUNNEL”! SWEDISH BOARD OF AGRICULTURE: A CRISPR-CAS9-MUTANT BUT NOT A GMO (13 May 2016)

    Are plants engineered with CRISPR technology genetically modified organisms? (14 June 2016)

    Brave New Crops: Gene Editing Comes to Agriculture (17 June 2016)

    Recent CRISPR News: 9/22/2016 – Titanic Clash Over CRISPR Patents Turns Ugly

    References

    Andersen, M. M., et al. (2015) “Feasibility of new breeding techniques for organic farming.” Trends in Plant Science, Vol. 20, pp. 426–434. DOI: 10.1016/j.tplants.2015.04.011 (Abstract)

    Belhaj, K., A. Chaparro-Garcia, S. Kamoun and V. Nekrasov (2013) “Plant genome editing made easy: targeted mutagenesis in model and crop plants using the CRISPR/Cas system.” Plant Methods, 20139:39, DOI: 10.1186/1746-4811-9-39. (Full Text)

    Cyranoski, D. (2015) “CRISPR tweak may help gene-edited crops bypass biosafety regulation.” Nature, DOI:10.1038/nature.2015.18590. (Full text)

    Khatodia, S., et al. (2016) “The CRISPR/Cas Genome-Editing Tool: Application in Improvement of Crops.” Frontiers in Plant Science, Vol 7, pp. 506. DOI: 10.3389/fpls.2016.00506 (Full Text)

    Quetier, F. (2016) “The CRISPR-Cas9 technology: Closer to the ultimate toolkit for targeted genome editing.” Plant Science, Vol. 242, pp. 65–76. DOI: 10.1016/j.plantsci.2015.09.003 (Abstract)

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