Did you ever realize the food you are eating might have been genetically engineered centuries ago?
Studies indicate that the ancient practice of grafting may have allowed even distantly related plants to swap all three kinds of genomes they possess.
Grafting refers to the transplantation of one plant into another so they can fuse and continue to grow.
Farmers have been grafting plants for thousands of years to combine, for example, a tree that bears delicious fruit with one that has disease-resistant roots. Grafting can also occur naturally when the branches press together.
One study has shown that cells on either side of a graft may have exchanged the chloroplasts. Whereas in another, it was found that the entire nucleus of a cell containing the main genome, could be transferred across grafts. The transferred nucleus can be added to an existing cell nucleus.
A research team led by Pal Maliga of Rutgers University in New Jersey has shown that cells also swap mitochondria – energy-generating organelles with a small genome of their own.
And once entire mitochondria from one plant get into the cells of another, they mix their DNA with that of the existing mitochondria.
This means all three kinds of plant genome can be swapped via grafts.
There are pieces of evidence that plants sometimes exchange mitochondria, but this study is the first to show it happening.
Since grafting has been widely used for millennia, it is highly likely that some of the plants we eat were created by unintentional genetic engineering by farmers.
Many crop plants have more than two sets of the chromosome. Also known as polyploidy, those plants usually attributed to genome duplication, but some cases could be evidence of genome exchange in grafted plants.
Nature blurring the lines
Some people may not support the idea of unintentional/accidental modifications of plants as they believe that grafting is not a genetic modification technique. This blurs the boundaries between man-made and natural genetic engineering.
While it is possible to modify chloroplasts and the nucleus genetically, there has been no way of altering mitochondria in plants so far.
Grafting is increasingly used for vegetable production, for instance, to boost yields by using plant varieties with more vigorous roots. Some more unusual combinations are also becoming available, for example as tomatoes are grafted into a potato root to create a crop that produces both.
Source: New Scientist