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.

Nothing ever changes

Except the buzz-words

Love from the Escapist

Moviebob gives us some love.

Note: It took 26 posts before some moron wandered in and pulled out the old ‘monsanto’s making farmers buy terminator crops’ lie, which is probably a new best time for rational responses.

Biotech basics 1: Introduction

The first genetic engineers were neolithic hunter-gatherers, who began selecting useful mutations in wild plants (by the simple expedient of saving and replanting their seed) to improve them for human use. This resulted, starting from around 10 000 years ago, in the invention of agriculture in the fertile crescent. This invention, independently made in a number of places since then, revolutionised the lifestyles of the people in the region, transforming them into the citizens of the first great civilisations.

There is a good case to be made, in fact, for farming being the driving force behind civilization itself: growing crops forced people to stay at a single place and led to the construction of towns and cities. The surplus of food produced be farming allowed the development of non-productive castes: kings, priests, soldiers, scribes and taxmen. Farmers, in essence, became the lowest rung of an entire chain of services (including extortion) that make up the basic elements of what we recognise as civilization.

For the longest time the slow, careful method of storing and replanting favoured individuals was the only means of improving crops. The discovery of the principles we now know as population genetics, however, allowed this process to be refined: Breeders could, by taking careful note of individual and population traits (along with their heritability, or ability to be passed on to descendents), determine the most useful crosses to use when selecting individuals. This, along with techniques to allow breeding even between distantly-related plants, made up the bulk of crop development in this century.

More recently still (starting in latter half of the 20th century), the application of emerging technologies allowed the creation of high-yielding crop lines. This was done using a number of approaches: dwarf phenotypes in wheat (caused by a defective gene for a specific plant hormone) and hybrid lines in maize (made by crossing two distantly-related maize varieties to take advantage of so-called hybrid vigour) for instance. The result, however, was phenomenal.

These advances (specifically those in wheat breeding, along with a number of new approaches in farm practices, pesticides and fertilizers) later became known as the green revolution. This revolution singlehandedly raised the farming productivity of the planet, almost doubling the amount of food that the world produced. Ironically, the new crops were not very popular with the nascent green movement. This is, it seems, a cyclical problem with new crop technologies: bitter resistance followed by placid acceptance a generation or so later. Which, of course, happens at the same time as bitter resistance against the new technology.

Most recently of all (from the mid 80s onwards), crop scientists began using new technologies developed to identify, isolate and characterise DNA to alter crops at a molecular level. These technologies, lumped together under the banner of ‘genetic modification’ are seen by crop scientists as the starting point for a new green revolution: one which could potentially have even more widespread and positive effects than the last one. As for the opponents of this new wave of biotechnology: see above.

For the really keen: a wikipedia run-down of the green revolution and an interview with one of my personal heroes (and a leading figure in the green revolution): Norman Borlaug

The technology of plant genetic engineering will be explained in part two.

Yet more debate

It looks like Pharyngula really went to town on the whole GMO debate recently.

Anyway, between the hand-wringing about Monsanto and the evils of industrialised agriculture, there seems to be a need to explain exactly what genetic modification is. I’ll be doing my best to do so for the next while, so hopefully the next time we have this debate we can get beyond the whole ‘they’re going to kill us all with super-weeds/terminator seeds/poison death-plants’ phase and move on to debating the more important stuff.

Wish me luck.

I’m back again… sort of.

Got some popular-blog/biotech love!

See, even pharyngula gives us crop biotech people some sugar every now and then…

 

PS: I promise to try and update more often in future. Don’t expect miracles, though

 

Cutessss

On a slightly lighter note, Ruth and I were having an argument over cute animals. I find puff adders, for instance, adorable. I would be cuddling one right now were it not for the fact that they are a) hard to housetrain and b) deadly venomous.

Anyway, I love the fat little guys. Also cute:

Leopard geckos

Giant salamanders

Regular salamanders

Namib geckos

Sungazers

Any other suggestions?

The failed horseman dies.

This man’s death is already becoming a political football and possibly marks the start of yet another round of white racist paranoia. Considering what he personally did (and incited others to do), I can’t say that I’m exactly devastated that he’s gone.

But I do wonder why it is that the most horrible people always get to be lauded and applauded when they go. It ruins my faith in humanity a bit.

Meta-Burton

I went and saw Alice in Wonderland today. My main thought (besides silently bemoaning the fact that I paid, again!, to have my childhood ruined) was that old Tim sure doesn’t do a lot of original stuff these days(Matt Bors agrees with me).

A bad time…

Speaking of which, again, I found this gem from 1960 as well. This would be pertinent to my previous post except gay people are still not accepted as fully human yet, making the whole ‘wait a few years before declaring that they’re now infringing on our rights’  thing rather a moot point.