Plant Genetic engineering: Current gene insertion technologies

The long-awaited part duex:

 

The technology of gene insertion in plants is around 30 years old now, the product of a wave of research in the 1980s. Eventually, two main technologies came to dominate the field: Biolistic and agrobacterium-based insertion. They are, with a few tweaks and upgrades, the same technologies we use today.

Biolistics, as the name implies, use ballistic particles (usually microscopic grains of tungsten or gold) to punch through the tough cell walls of plants and deposit DNA (which is carried as an outer coating) into the nucleus. This process is fairly inefficient, with only a small fraction of cells being hit in the right manner to transfer a functional copy of the construct into the genome. Even in these few cases, the insertion is often fragmented, or else contains multiple copies of the construct. This inefficiency, in addition to the rather limited types of plant matter that can be used (almost always embryogenic cultures of cells rather than intact plants or whole tissues) means that biolistic insertion has slowly lost ground to its long-time rival: agrobacterium. Its great advantage, however: the fact that the process is not limited in terms of what species it can transform, will keep it on the front lines as a niche system for the foreseeable future.

 

Agrobacterium-based methods make use of an engineered version of the gall-forming bacterium: Agrobacterium tumafaciens. This clever little bug is able to use a special DNA carrier (the T-plasmid) to introduce DNA into its host. Normally, this DNA would contain genes to make the plant cells form galls and produce food for the bugs, but engineered versions have had this cut out and replaced with cloning sites to insert other genes. The result is a simple system that produces transformed plants with high efficiency. Unfortunately, the little guys are sort of finicky when it comes to what species of plants they will play with. This has been especially problematic for the cereals (wheat, rice, barley and the like), which are all grasses that Agrobacterium is normally not interested in. Recent advances have thankfully overcome this somewhat, so the future of this little bug is bright.

 

Of course, the field of gene insertion is not static. Both systems, good though they may be, have significant limitations in terms of their ability to target genes to specific places on the genome and also have trouble when being used to insert multiple genes. As these abilities are both going to be very important for the next wave of plant genetic engineering, a lot of research has been done to find something better. I’ll cover these future gene insertion techs in the next segment.

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: