Modifying tobacco to create enzymes

US researchers have genetically engineered tobacco plants that can produce medical and industrial proteins in the field.

This successful move outdoors from a laboratory setting could provide the opportunity to grow in bulk, thus making the whole concept economically feasible.

Industrial enzymes and other proteins are currently made in large fermenting reactors. Making them in plants could reduce production costs by three times, suggest the researchers from Cornell University and the University of Illinois. 

They say the market for biologically derived proteins is forecast to reach US$300 billion in the near future.

Conventional wisdom suggests the burden of asking plants to turn 20% of the proteins they have in their cells into something they can’t use would greatly stunt growth. That didn’t prove to be the case, however. {%recommended 7112%}

“When you put plants in the field, they have to face large transitions, in terms of drought or temperature or light, and they’re going to need all the protein that they have,” says Cornell’s Beth Ahner. 

“But we show that the plant still is able to function perfectly normally in the field [while producing non-native proteins]. That was really the breakthrough.”

It’s still early days, but Ahner and colleagues are encouraged by their findings, which are reported in the journal Nature Plants.

In their study, they modified the tobacco plants to produce the cellulase protein Cel6A, which belongs to a large group of related enzymes used in such things as manufacturing laundry detergents and processing of food and animal feed. 

The genetic engineering was achieved by delivering DNA with instructions for making a desired protein into the chloroplasts of plants cells. The plants containing chloroplasts that adopt this DNA are then cultivated. 

Chloroplasts are the photosynthesizing organelles in plants and contain their own DNA. Plant cells cannot make their own chloroplasts but inherit them from each daughter cell during cell division.

This design, the researchers say, helps prevent plants with designer proteins grown in the field from contaminating other tobacco plants and relatives through the spread of pollen, which is contained in the stamen, the male portion of the plant.

“One of the advantages of the technology that we’re using is that the chloroplasts in most crop plants are inherited through the maternal line, so the genes are not in the pollen,” Ahner says. “The pollen is one of the main concerns for dispersal to other transgenic crops.”

In future work, the team will investigate how to get plants to consistently produce different types of proteins. 

“We’re trying to understand the basic biological mechanism that allows any protein to be accumulated” in a genetically modified plant, Ahner says.