Some compounds that determine plant species' characteristics such as the taste of tomatoes can be engineered to produce larger quantities in plants that have few or none of them, researchers at Purdue University have found.

Tomatoes available in the Northern states typically are grown in warmer climates, such as in Florida, California and Mexico, and harvested immature and still green so that they can ripen during or after shipment. But picking them before they are ripe affects their flavor, which has led to complaints from consumers.

"The research ultimately could lead to a variety of uses, such as in improving the taste of fruits including fresh-market tomatoes, in increasing the resistance of plants against pests or diseases, or in producing certain flavors, fragrances and pharmaceuticals," said Natalia Dudareva, distinguished professor of biochemistry.

The research involving metabolic engineering also was conducted by Purdue postdoctoral research associate Michael Gutensohn, with collaborators at the University of Michigan and in Israel. It was published in the August edition of The Plant Journal as the cover story.

Terpenes, a class of volatile compounds, are important because they often determine how fruits taste; how the flowers of a plant smell, thus attracting pollinators; and what characteristics plants might have to repel or defend themselves against pests.

The goal in the research was to determine how metabolic engineering can be used to produce large quantities of monoterpenes, a particular group of terpenes, to improve taste and aromatic qualities of fruits.

The researchers at Purdue used tomato fruits for their metabolic engineering studies to increase production of monoterpenes. Tomatoes are an ideal system for this research because during ripening they accumulate large amounts of carotenoids, the red pigment giving these fruits their characteristic color.

Carotenoids and terpenes are made from the same molecular building blocks, which allowed the researchers to tap into the pool of building blocks naturally available in tomato fruits and then engineer the production of monoterpenes.

The researchers learned that the largest quantities of monoterpenes were obtained through the combination of two enzymatic steps. In the first step, two of the available molecular building blocks are fused together to build an intermediate product. In the second step, the chemical structure of this intermediate is further modified, leading to the formation of monoterpenes.

The research was funded by grants from the Agricultural and Food Research Initiative of the US Department of Agriculture and the United States-Israel Binational Agricultural Research and Development Fund.

Source: Purdue University news release