Molecular research ensures breath of fresh air
By means of genetic modification, it is possible for plants to make highly specific aromatic substances (terpenoids). This is the conclusion of the thesis by Plant Research International employee Mazen K. El Tamer, for which he obtained his doctorate from Wageningen University on 27 November 2002.
Combining molecular biological research with cell biology, biochemistry and sensory research, El Tamer demonstrated the possibility to make tobacco leaves smell differently via genetic modification. El Tamer identified a number of enzymes which are responsible for the production of monoterpenes, and then the part of these enzymes responsible for the specific biochemical reaction that they perform. This information offers the potential to improve crops that produce specific terpenes, whereby they will smell and/or taste better, or be resistant to diseases or pests.
Citrus varieties are important crops economically. Their notably pleasant taste and smell is partially caused by the presence of terpenoids. These terpenoids may also play a role in the resistance to threats such as insects and fungi. The enzymes called terpene synthases are responsible for making terpenoids. From lemon, El Tamer isolated DNA that codes for a number of these enzymes. He then tested tobacco plants genetically modified with this DNA. With the help of a human panel, El Tamer proved that the smell of the genetically modified tobacco leaves had indeed changed compared to the wild variety.
As a part of his research, El Tamer isolated, characterised and described four new monoterpene synthases. Each is responsible for the production of one specific monoterpene. Using domain swapping experiments, it was possible to ascertain the basis for the specific differences between the monoterpene synthases. Domain swapping experiments involve the exchange of fragments from two DNA's. Repeated checks are made as to whether the DNA still codes for an enzyme that is capable of making the specific monoterpene. Via these experiments, El Tamer ascertained a domain of 200 amino acids on the enzyme upon which the product specification is based. He then suggested that just 2 amino acids differentially positioned on the enzymes are important for that specific role.
El Tamer's work has considerably enhanced our understanding of the process of molecular regulation of monoterpene biosynthesis in plants. Further research into the effects of monoterpene synthesis may have major economic implications. The aromatic substances could entail an important change to the plants if, due to these terpenoids, they would become more resistant to diseases and pests. Moreover, the aromatic and flavouring industry is likely to have an interest in increasing the production of certain terpenoids.
List of press releases for 2002