New study shows that promoter used in GM crops works in salmon over time


Salmon swimmingA new study in salmon has confirmed for the first time in a vertebrate that the S35 CaMV promoter, such as is used in most GM crops, is able to drive expression of a transgene, and that the duration of transgene production is at least 1.5 years in the salmon.  

In this study Tore Seternes and Roy A. Dalmo (UiT the Arctic University of Norway), Tom Christian Tonheim (Marine Harvest) and Anne I. Myhr (GenØk) found that the plant virus promoter CaMV can also drive expression of a transgene (reporter gene: luciferase) in Atlantic salmon. The promoter is derived from “Cauliflower mosaic virus” (CaMV) and is often used in genetically modified plants. Not only did the promoter give expression of the fluorescent protein (luciferase) shortly after injection of the DNA construct, but production lasted over one and a half years. This is as long as the life cycle of the farmed fish. They found that the DNA construct was intact at the injection site throughout the research period.

This is the first study that has shown that a plant virus promoter is also active in animals in vivo, and this promoter can therefore be an alternative to some of the other promotors used in DNA vaccines. Canada has approved a DNA vaccine that can be used to protect salmon against IHN virus and the European Medicines Agency just granted marketing authorization for a DNA vaccine that can protect salmon against pancreas disease (PD). There are many advantages of DNA vaccines; they are easy to produce, and a DNA vaccine can be used as a starting point by replacing a gene with a new gene from the virus or bacterium (possibly infectious agent) one wishes to prevent disease from. Until now, virus promoters that infect animals are frequently used in experimental DNA vaccines for fish. One example is the cytomegalovirus (family: Herpesviridae) promoter (CMV promoter), which is a strong promoter that can drive the expression of a desired disease protective antigen. The CMV promoter is, however, not desirable to use in DNA vaccines, as it is known that e.g. human cytomegalovirus may produce undesirable effects.  Consequences of the long survival of the plant DNA may be that one achieves a much more prolonged protection by using DNA vaccines than anticipated. Secondly, that one should have good knowledge of proteins and products produced by the genes in the DNA vaccine, and which effect they have on salmon.

Seternes, T., Tonheim, T.C., Myhr, A.I. & Dalmo, R.A. (2016). “A plant 35S CaMV promoter induces long-term expression of luciferase in Atlantic salmon”, Scientific Reports 6, Article number: 25096. doi:10.1038/srep25096

Foto: Arrlxx/Adobestock