A fungus plague has been attacking the American Chestnut tree population for over 100 years now. Scientists have been trying everything to save the tree from extinction.
I wrote about one approach back in 2009:
Really innovative idea– Infect fungal infected trees with fungus… infected with a virus. The virus infects the infecting fungus, and weakens it so the trees immune system can kill it. Very cool, but complicated.
The other idea I mentioned in that post was to cross-breed the American tree (susceptible to the fungus) with its Chinese cousin (not as susceptible to the fungus). This approach has been difficult to perfect– scientists want to get the bare minimum number of genes required from the Chinese genome, while maintaing the resistance. So, if you cross the trees once, approximately half of the offsprings genome will be Chinese chestnut, and half will be American chestnut. If you are lucky, the Chinese half will contain all the genes necessary for resistance. Then, you have to cross that offspring with another American. Approximately one quarter of the offsprings genome will be Chinese, and three-quarters American, and if you are lucky, the Chinese quarter will contain all the genes necessary for resistance. This keeps going on and on and on, until you get a tree that is 99.99999 American Chestnut, and only the fungus resistance genes from the Chinese chestnut.
This process requires a lot of time. Chestnut trees arent fruit flies. It also takes a lot of luck. Luck isnt something you want to have as a factor in your experiments, and its not something you want to rely on to keep a species alive.
Why dont we save a lot of time and take ‘luck’ out of the equation by generating a genetically modified American Chestnut tree? Just put The Right Genes into the genome of the American Chestnut?
Heres a problem: The Chinese Chestnut tree is resistant to the pathogenic fungus thanks to numerous genes working together.
Thats not fun from a GMO perspective.
You have to get more genes in, expressed at the right levels in the right tissues, and then when that GMO tree crosses with another tree, the offspring might lose one/two/all the necessary genes. Thats not ideal.
So, these researchers took *one* gene, from wheat, that could do the same job as the seven genes from the Chinese Chestnut!
Oxalate oxidase wipes out the oxalic acid the pathogenic fungus needs to cause trouble. When oxalate oxidase was expressed in GMO chestnut leaves, it could kinda protect the leaves. Kinda. I mean it did compared to ‘wild’ American chestnut, but not nearly as well as the network of genes that protect the Chinese chestnut.
So this is not a perfect solution. Yet.
But ‘kinda’ is an extremely positive starting point. Its a position that can be improved upon in the future. This paper suggested that increasing the expression levels of oxalate oxidase might be enough to not only protect the American chestnut just as well as the natural network in Chinese chestnut, but actually push resistance beyond what is found in the Chinese Chestnut!
GMO American chestnut, like GMO papaya, might just save a species from going extinct.