The researchers have developed a technique to genetically modify Agaricus bisporus - the button variety of mushroom, which is the predominant edible species worldwide. Transgenic mushrooms can be used as factories for producing therapeutic proteins, such as vaccines, monoclonal antibodies, and hormones like insulin, or commercial enzymes, such as cellulase for biofuels.
To create transgenic mushrooms, researchers attached a gene that confers resistance to hygromycin, an antibiotic, to circular pieces of bacterial DNA called plasmids, which have the ability to multiply within a bacterium known as Agrobacterium. The hygromycin resistance gene is a marker gene to help sort out the transgenic mushroom cells from the non-transgenic cells, explained Charles Peter Romaine, who holds the John B. Swayne Chair in spawn science and professor of plant pathology at Penn State.
"What we are doing is taking a gene, as for example a drug gene, that is not part of the mushroom, and camouflaging it with regulatory elements from a mushroom gene. We then patch these genetic elements in the plasmid and insert it back into the bacterium," he added.
The researchers then snipped small pieces off the mushroom's gill tissue and added it to a flask containing the altered bacterium. Over the course of several days, as the bacterium goes through its lifecycle, it transfers a portion of its plasmid out of its cell right into the mushroom cell, and integrates the introduced gene into the chromosome of the mushroom.
Next, the researchers exposed the mushroom cells to hygromycin. The antibiotic kills all the normal cells, separating out those that have been genetically altered for resistance. The test demonstrates that if a second gene, insulin for example, were to be patched in the plasmid, that gene would be expressed as well.
MEDICA.de; Source: Penn State