Vaccine-producing ‘plant-factories’

Amongst other applications, these can be used to produce oral vaccines which, upon being ingested, will be able to immunise against diseases. Moreover, this discovery opens the door to the design of protein-manufacturing plants of great interest therapeutically and in the development of vaccine antigens.

This discovery, published in the latest issue of The Plant Cell, contributes, moreover, to refuting one of the current scientific dogmas regarding the mechanisms of protein transportation in plant cells.

The research was carried out by a team from the Institute of Agrobiotechnology and Natural Resources (a centre jointly run by the CSIC, the Public University of Navarre and the Government of Navarre), made up of Javier Pozueta, Francisco José Muñoz and Edurne Baroja. These scientists have been aided by a research team from Niigata University (Japan).

Specifically, the study describes a new route for the traffic of proteins from the reticular/Golgi system where there are glycosylates, towards the chloroplasts of the plant cell. Some of these glycosylated recombinant proteins have significant antigenic power of great pharmaceutical interest.

Conventional biotechnological methods enable the cells to accumulate very limited quantities of glycosylate recombinant proteins. The chloroplast is a cell organ with great capacity for storing proteins. However, it is incapable of producing glycosylate proteins.

The newly discovered route connects the cell organ where the proteins are glycosylated, the reticulum, with the chloroplasts. This discovery signifies the first step in the development of plants and algae that accumulate in their chloroplasts large amounts of glycosylate recombinant proteins with significant antigenic power.

By chance

The new route discovered by the CSIC team refutes one of the dogmas regarding this type of protein. Nevertheless, Pozueta reveals that the starting point for this research was a chance discovery. The team had been investigating the metabolism of starch, a substance that is generated in the chloroplast, when they came across an unexpected type of protein for this type of cell organ.

They found that these proteins resisted high temperatures and withstood extreme conditions, characteristics of glycosylate proteins. The discovery was unexpected because the literature written to date does not contemplate the presence of this type of protein in the chloroplast.

Once the presence of this type of protein in the chloroplast was ascertained, the scientists asked themselves if it were the cell organ itself that was glycosylating. This focus gave rise to finding a new route of traffic between the reticulum and the chloroplast. Up to now it has been argued that the endoplasmic reticulum was connected to other parts of the cell such as the Golgi apparatus and the plasmatic membrane, etcetera, but not to the chloroplast.