Researchers using genetic modification to try to revive American chestnut trees

Researchers in the American Chestnut Research & Restoration Project at State University of New York-Syracuse who have created genetically modified chestnut trees are hoping to help revive the tree that has been mostly wiped out by a fungus, Jill Neimark reports for NPR. "Researchers have bequeathed the chestnut a highly protective gene that bananas, cocoa, wheat and barley have already evolved on their own. So far the transgenic seedlings are proving to be at least as resistant to blight as the hybrid or Chinese chestnuts currently under cultivation in the U.S." (SUNY photo: Linda McGuigan examines a batch of transgenic American chestnut plantlets in a high-light chamber)

Other groups who have worked to revive the tree have been slowed "by the fact that a panoply of seven genes protects the Asian tree, and all must transfer," Neimark writes. "Some chestnuts also only tend to succumb to blight after five or ten years, so the foundation must grow the latest generation of trees—which are only 1/16th Chinese—for at least a decade before they can feel confident enough to release seeds to the public."

At SUNY, "scientists transplanted a gene that wheat, barley, cocoa and some fruits already use to protect themselves against fungus," Neimark writes. "The gene makes an enzyme to degrade an acid produced by the fungus, rendering the fungus harmless. Using special laboratory techniques, the scientists transplanted this gene into chestnut embryos, harvested the few cells that took up the gene and used those cells to grow a new embryo, nourishing it with all the nutrients it needs to become a 'plantlet' or seedling."

"The first generations of plantlets proved hardy but not fully immune, so the scientists replaced a genetic 'dimmer' switch inside the gene to turn it up so it would produce more enzyme," Neimark writes. "The latest generation of plantlets have proved more resistant than American chestnut seedlings and hybrid seedlings, according to SUNY forest biotechnologist Andy Newhouse. And, he says, the newer transgenic trees have a similar level of blight resistance as Chinese chestnuts."

Newhouse said they have about 1,000 plants, some two to three years old and as tall as six feet, Neimark writes. "The ultimate plan is to plant about 10,000 transgenic seedlings and grow them big enough to produce enough pollen to pollinate other 'wild' and vulnerable American chestnuts." (Read more)