In order for a gene to create a protein, the gene's DNA must first be converted into what's known as messenger RNA. These RNA molecules are the instruction manuals that show the ribosomes the cell's protein factories how to build a protein. A few years ago, scientists studying bacterial cells discovered sections in certain messenger RNAs that metabolic products (metabolites) can bind to. In doing so, they induce the RNA molecule to change its spatial structure and make it possible to switch protein production on or off. For the bacteria, these sections the riboswitches provide a fast and efficient way of controlling protein synthesis. Unsurprisingly, it had previously been impossible to demonstrate the presence of such riboswitches in the chloroplasts of plant cells.
Max Planck scientists based in Golm near Potsdam were recently the first to modify and insert riboswitches into the genetic material of the chloroplast in order to control the formation of certain chloroplast proteins. The scientists smuggled a gene into the chloroplast DNA and equipped it with a riboswitch. Theophylline, a substance found in the tea plant, was used as the "switch": it has the capacity to bind to the riboswitch on the messenger RNA, thereby enabling the chloroplast ribosomes to read the RNA. "When we spray the tobacco plants with theophylline, we find that the chloroplasts form the corresponding protein. In the absence of theophylline, no protein is produced. So the theophylline riboswitch allows us to switch a gene on or off at will and see what effects result," explains Ralph Bock from the Max Planck Institute of Molecular Plant Physiology. This had previously been a difficult thing to achieve, given that the chloroplast genome contains numerous genes which are essential for survival. Switching one of these genes off permanently would result in the death of the cell, rendering it useless for further investigation.
However, studying the way chloroplasts work
|Contact: Ralph Bock|