Research paper p 1303-1306


A gene amplifier for plants


A small piece of DNA from tobacco plants could turn out to be a big boon to plant researchers. The task of introducing foreign genes into plants and getting them to express sufficient amounts of the protein of interest is often very hit and miss. Sometimes insufficient copies of a foreign gene insert into plant chromosomes; other times, a foreign gene does not produce detectable protein due to a process called gene silencing. Now Ilya Raskin and his colleagues have identified an amplification promoting sequence (aps) from tobacco that increases the number of copies of a foreign gene and stimulates expression of the protein it encodes. The DNA sequence shows great potential as a tool for enhancing gene expression in GM plants created for agricultural uses and molecular farming.


To date, several types of gene amplification sequences have been identified in mice and mammalian cells, but none had been found in plants. Raskin and his team set about finding a plant aps by searching unstable regions of the tobacco plant genome for sequences that looked similar to the gene amplification elements found in other organisms. They identified a sequence (aps) that contained AT-rich sequences typical of a mouse DNA amplification element and a short sequence similar to a DNA amplification element from yeast. When they joined this aps to a   herbicide resistance gene (acetolactate synthase) or to another gene encoding jellyfish green fluorescent protein, the number of genes inserted in plant chromosomes increased, often leading to a concomitant increase in protein expression. In the case of herbicide-resistance the genes, Raskin's team showed that the effects were stably inherited in seeds, and that plants germinating from the seeds containing the aps also were herbicide resistant. The aps sequence therefore shows great promise for circumventing some of the problems of gene silencing, which results in many GM plants produced by traditional genetic engineering techniques losing expression of the gene of interest.