Enter the Hornworms

So far, we’ve been focused on introducing a specific genetic trait into our target tobacco plants. In our last report, we found that our target trait was successfully expressed in the plants.

But separately, away from the gene gun and carefully tended tobacco plantlets, our project researchers have also been nurturing a batch of tobacco hornworms.

The tobacco hornworm larva is a caterpillar about 70 millimeters long. It’s named for the obvious horn or spike that grows on its abdomen. At this stage of its lifecycle, there’s nothing it likes more than feasting on tobacco leaves. Just one or two larvae can defoliate an entire tobacco plant; they are capable of vast destruction.

Once the larvae complete development, they begin “wandering” or looking for a place to burrow. Underground, they move into the pupal stage of life. When they emerge, the adult form of the tobacco hornworm is known as a Carolina Sphinx moth or hawk moth.

Our batch of hornworm caterpillars will be introduced to our transformed tobacco plants, under controlled circumstances. We’ll watch as the hornworms munch away on the transformed tobacco plants.

“In these feeding trial, we’ll be looking to see if the RNAi expressed in transgenic tobacco chloroplasts is effective as an insecticide,” said Jeffrey Staub, Ph.D., a TechAccel science advancement program manager, who is working with partners on this “Biosprey” project at the Danforth Center for Plant Science.

If the project is successful, the tobacco hornworms won’t survive the feeding. The RNAi expressed in these transgenic tobacco plants will have disrupted the immune system in the hornworm gut, leading to the death of the worms.

The project is nearly done. We’re confident that we’ve identified the genetic material that can effectively disrupt the tobacco hornworm lifestyle. The next phase will work on turning that genetic material into a sprayable substance that can be topically applied to plants as a biopesticide – lethal only to the tobacco hornworm.

Another next step will entail repeating this entire process on another target pest and crop.

Watch out, Diamondback moth – we’re coming for you next.

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