GMO Tools of the Trade: The Gene Gun

I think I have pretty cool job.  I work in a lab with other amazing scientists making transgenic plants.  I hope the time and effort that goes into finding the right genes, making the plants, growing the plants, and getting seed into the farmers' hands are going to enable them to do their jobs more efficiently.  We all know that life throws challenges at us on a daily basis.  Farmers are no exception.  Some of their biggest challenges include weeds, pests, and diseases.  I, and all of us, do our job because we want to equip farmers with tools to overcome those challenges and continue to increase yields.

Lots of people I talk to want to know how we make transgenic plants.  There are many protocols that we use that vary from crop to crop and from company to company.   However all of these protocols are going to have a step that involves gene delivery.   In order to make a transgenic plant, we need to insert a gene of interest, say resistance to a particular insect, into the target's genome.

"Genegun". Licensed under Public Domain via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Genegun.jpg#/media/File:Genegun.jpg

Different types of delivery methods exist; there are two methods I have used in my career.  The one I want to go over in this post is the biolistic method that uses a "gene gun".  The gene gun is a very interesting invention.  What if you could propel DNA into a cell at such a high speed it would incorporate into the target cell's chromosome so that the transformed cells will express that new gene?  Some minds at Cornell University and DuPont did just that with a "gene gun."  There prototype involved using a modified Crossman air pistol to fire small tungstun particles that were coated with a lots and lots of copies of a gene.  The idea worked and the gene was expressed when propelled into onion cells.

The technology continued to advance and the gene gun was manufactured in some limited quantities.  One model involved using a modified 22 cal nail gun cartridge to propel the DNA.  As you can imagine, finding a safer alternative to explosive propellants was probably a good idea.  The gene gun I am most familiar with is the one pictured below manufactured by BioRad under contract from DuPont.   The propellant was indeed replaced with Helium.  The gene of interest is coated in gold or tungstun particles and loaded on a rupture disc.  The rupture disc is attached at the top of the chamber.  The plant material is placed under the disc in the bottom of the the chamber.  Close the door, build the pressure up, and Fire!  The pressure ruptures the disc and the DNA-coated particles are blasted down into the plant material.  From that point, the DNA will be incorporated into the genome of your target plant cells.  It is not the most efficient system.  Only some cells will be transformed and there are other downfalls.  However, I am always amazed at this piece of technology and the progression from prototype to the model that can still be found in some labs today.




Great youtube video showing how the gene gun is prepped:

Short youtube video showing the gene gun being fired.