James and the Giant Corn Rotating Header Image

November 11th, 2009:

bt: The Bacteria and the Protein

I figured if I am going to do a review of genetically engineered crops, I needed to address the other major traits besides resistance to herbicides presently on the market. This one addresses a family of proteins found in the bacteria Bacillus thuringiensis that can kill insects.

Anyone who reads about the public policy debates swirreling around genetically engineered crops will be familar with the two letter abbreviation ‘bt’ as in bt corn, bt cotton, bt ginseng (the last is fictional). What always surprises me is that some people STOP reading before they come across an explanation of what bt stands for. Just typing bt into google won’t bring up a relevant result until the 30th hit (two letters just isn’t very unique). I have talked with people who are convinced bt stands for everything from biologically treated to BioToxin. It doesn’t.

Golden Eyed Lacewing Adult. It's not much use, but the larva vicious predators of certain plant pests. (Photo public domain courtesy of USDA. You guys are awesome!)

Golden Eyed Lacewing Adult. It's not much use, but the larva vicious predators of certain plant pests. (Photo public domain courtesy of USDA. You guys are awesome!)

The name actually comes from a species of bacteria called Bacillus thuringiensis. Different substrains of the species carry different members of a family of genes that code for Cry proteins (and separately can also carry genes that code for Cyt proteins*), which can kill insects. Finding chemical or biological means to kill insects isn’t that hard. What makes the Cry proteins noteworthy is how selective they are in their killing. A given Cry protein is dangerous to only a small subset of insect species. And that’s important, because, for every** western corn rootworm, european corn borer, or earworm there are also benign or even beneficial insects in and around fields like lacewings, trichogramma wasps, or those rootworm eating nematodes I talked about a couple of days ago, which aren’t insects, but also harmed by insecticides. (Agro-ecology is beyond my field of expertise, had to call up my tipster from the previous post to get this list) When a crop is genetically engineered to produce one of the dozens of Cry proteins discovered in Bacillus thuringiensis, it replaces or reduces the spraying of insecticides to control insect pests, with positive effects on insect biodiversity. (more…)

Spam Wave

I’m getting hit by completely nonsensical spam comments (nothing that looks like words in any language, no working links) at a rate of close to one per minute. As a result I’ve had to reactivate my spam filter, the same one that was misbehaving earlier. If you’re comments aren’t showing up, drop an e-mail to jcs##@jamesandthegiantcorn.com (replacing the ## with the sum of 23 and 75).

Please let me know if you have any idea what might be causing this upswing.

Genetically Engineered Crop: Blue Carnations

Florigene's Moondust carnations, one of several violet and blue varieties they've created with genetic engineering. Photo by Pagemoral and licensed under the creative commons. Click to see the photo in its original context with license information

Florigene's Moondust carnations, one of several violet and blue varieties they've created with genetic engineering. Photo by Pagemoral and licensed under the creative commons. Click to see the photo in its original context with license information

Scientific Name: Dianthus caryophyllus

Genetically Engineered Trait: Anthocyanin biosynthesis (blue and violet plant pigments)

Details of Genetic Engineering:

The market in flowers with genetically engineered colors is (to my knowledge) occupied by a single Australian company called Florigene. They study anthocyanins, the class of plant pigments responsible for, among other things, the coloration of purple potatoes, purple carrots, black rice, purple corn, and many blue and purple berries. Anthocyanins are one of the key classes of plant pigments, found to greater or lesser extent in most flowering plants.* Florigene has been producing purple and sometimes blue carnations since the 1990s by adding key enzymes in the anthocyanin pathway from other plant species. While purple carnations are cool, the real goal of Florigene’s work has been blue (and purple, and violet) roses, something rose breeders have been trying and failing to create for centuries.

Florigene was granted a license to grow their first breed of genetically engineered blue rose this summer, (although as far as I can tell the roses aren’t yet for sale, so they don’t get their own post). For more on plant pigments, Florigene, and why the development of blue roses as foiled breeders for so long, check out this fascinating post by MAT Kinase.

Purple potatoes with orange carrots (and did you know most carrots where white when they were first domesticated?)

Purple potatoes with orange carrots (and did you know most carrots were white when they were first domesticated?)

About Carnations:

Carnations belong to the caryophyllales, an extended family of plants that include cacti (cool), rhubarb (tasty), and carnivorous plants like sundews and venus fly traps(awesome!). Beyond that, I’ll admit I don’t know much about their biology.

If you know someone who is into flower meanings (I used to date a girl who was), you’ll notice there is no definition on record for blue carnations. It makes them the perfect gift to say, “I like you, so I bought you flowers” without having to worry about any unintentional subtext beside: “I’m also a huge plant/genetics geek, and if you don’t ask me soon how they make the flowers blue I’m going to burst!”

*The extent of anthocyanin biosynthesis in flowering plants is a good indicator that the ancestor of all the flowering plants alive today (which lived sometime between 250 and 100 million years ago) already contained the genes needed to produce anthocyanins, and flowering plants which are unable to produce them today, like roses, cannot because their ancestors lost the ability.