In the United States, the Animal and Plant Health Inspection Service (APHIS) regulates genetically modified (GM, genetically engineered, GE) crops and livestock. Heidi Ledford at Nature tells us about loopholes which some researchers now use to avoid the long, costly process of obtaining approval from APHIS.
I’ll focus here mainly on plants. APHIS enforces law based on technology which was the way to do GM in the 1980s but which isn’t the only method now. Here’s a summary of how GM can be done. To ‘transform’ cells (that is, to add new genetic material) you can use a bacterium, a gene gun or a protoplast.
The bacterium used for GM is called Agrobacterium tumefaciens. It’s a pathogen which inserts DNA into its host (victim) where the DNA stays even when Agrobacterium has gone. Dengephil at Plantwise explains how Agrobacterium works. Its ability to transform plant cells is useful for the bacterium and it’s proved useful for plant breeders too.
The gene gun (gene cannon) was invented by John Sanford and colleagues. Here’s the science. Here’s a film about how a gene gun works. A gene gun gets past any preference that Agrobacterium has about which plants it can transform but the gun acts at random.
Jared Keefer at Washington University compares Agrobacterium with gene guns. He says that Agrobacterium prefers to invade the cells of dicots (dicotyledonous plants, many of whose fruits and tubers we eat.) It’s not so keen on the cells of monocots (monocotyledonous plants, whose grains we eat and whose leaves are food to grazing livestock.) But this can be overcome in the lab. Dr Keefer says, ‘Transformation via Agrobacterium has been successfully practiced in dicots… Recently it has been adapted to and effective in monocots.’ Still he likes bacterial transformation because you can place what you want, where you want it. ‘In general, the Agrobacterium method is considered preferable to the gene gun, because of a greater frequency of single-site insertions of the foreign DNA.’
The protoplasts used for GM are plant cells with their cell walls stripped off. They’ll fuse with one another quite easily. This is useful to the plant breeder because it lets you hybridise species that wouldn’t breed naturally with one another. Here’s some science about protoplast fusion as agricultural biotech. Back in 1983, David Evans wrote there that ‘The unique gene combinations made possible by protoplast fusion ensure that new plant varieties will soon be derived from somatic hybridization.’
So biotech still uses the bacterial method to transform cells, sometimes, but it can use gene guns or protoplast fusion instead. Or as well. When you think of this from a commercial perspective there’s more to it than the excitment of making better crops in the lab. If you want to sell GM plants in the States, if you use a gene gun or protoplast fusion you might get past APHIS. Heidi Ledford at Nature shows us a list of GM plants which APHIS wouldn’t regulate because a plant pest (that is, Agrobacterium) wasn’t used to make them. That attitude isn’t very scientific, but to sell what you make, you have to obey the law.
A few months ago I asked whether GM crops are out of date. Biotech has other tools including Marker Assisted Selection (MAS, Marker Assisted Breeding, MAB) with or without mutagenesis (mutation breeding, MB). But GM is here to stay, in several forms. I think APHIS needs to catch up with developments in GM technology.