Epigenetics – beyond genes

Box 2 | RNA interference and plant technology

Hairpin RNA interference (RNAi) is a gene silencing technology developed by CSIRO that is used to develop new plant traits. It makes use of the ability of RNA to fold back on itself to form a ‘hairpin’ shaped piece of double stranded RNA. The hairpin RNAi triggers the cell’s RNA interference mechanisms to degrade messenger RNA from the target gene, reducing or completely silencing its expression.

Hairpin RNAi has been used to create plants such as the blue rose, virus-resistant wheat and barley, and cottonseed that makes healthy food oils.

Hey true blue

While roses have long been available in a wide range of colours, the holy grail of rose breeders, the blue rose, has proved impossible to achieve using standard plant breeding methods. Victoria-based company Florigene Pty Ltd have used hairpin RNAi to create the world’s first true blue rose. These roses have their natural pigment removed by hairpin RNAi, and genes from the pansy and the iris added to allow them to make a blue pigment instead.

Virus resistant wheat and barley

Hairpin RNAi has been used to develop varieties of wheat and barley that are immune to yellow dwarf virus. By targeting segments of viral genes with RNAi, the transgenic cereal plants are made immune to this costly disease.

Healthier cottonseed oil

Cottonseed oil is used to make cooking oils and margarines, but the process used to treat the oil to prolong shelf life and make it suitable for cooking creates unhealthy trans fats, which raise blood cholesterol levels. Using harpin RNAi, CSIRO has developed a cottonseed oil that is high in oleic acid, which makes it suitable for cooking purposes without the need for treatment.

Genetic research

RNA interference is providing scientists with new tools to study the function of genes. By observing the effect of ‘knocking down’ (reducing) or ‘knocking out’ (eliminating) the amount of a protein, researchers can deduce its normal function in the cell. RNA interference offers advantages over the traditional method of inducing mutations to silence genes, because it can be used to reduce, rather than completely eliminate, gene function. This allows researchers to study the function of gene products whose complete absence results in the death or severe malfunction of the cell.

Boxes
Box 1. RNA interference and epigenetics
Box 3. The Human Epigenome Project

Related sites
About CSIRO’s hairpin RNAi (CSIRO, Australia)
Healthier cottonseed oil (CSIRO, Australia)
Wheat with immunity to Barley Yellow Dwarf Virus (CSIRO, Australia)
World’s first blue rose (CSIRO, Australia)
Omega-3 oils in grains (CSIRO, Australia)

External sites are not endorsed by the Australian Academy of Science.
Posted September 2006.