What the Nose Knows - Avery Gilbert [110]
If there is anything more dispiriting than a flavorless tomato, it is a scentless rose. Along with chrysanthemums, tulips, lilies, and carnations, roses are the top sellers in the cut-flower market, with worldwide sales estimated at $40 billion a year. Where has all the fragrance gone? There are more than a hundred species of roses, yet most of those in commercial production result from crosses between only eight species. Like tomatoes, these varieties were not selected for fragrance, but for traits that the cut-flower industry prizes: flower color and shape, yield, vase life, and resistance to insects and disease.
Perfume chemists analyze floral scents down to the last molecule, but it’s not their job to find out how plants make the scent in the first place. Nor were academic researchers interested: in 1994, not a single floral scent enzyme had been identified. Then the biologist Eran Pichersky began to study a native California wildflower known as Brewer’s Clarkia. This unusual species—a night-blooming, moth-pollinated evening primrose—grows in only the San Francisco Bay Area. Pichersky’s team chemically characterized its scent and found that one ingredient—linalool—is produced by an enzyme called linalool synthase. When they successfully identified the gene that produced the enzyme, they opened up a whole new scientific field: floral scent biochemistry.
Since then, Pichersky and others have looked for the scent-producing enzymes in the Fragrant Cloud rose, and the genes that code for them. They hope to transfer those genes into a scentless rose like the Golden Gate cultivar.
Biotechnologists may ride to the rescue of rose scent. They have a toolbox full of techniques to transfer genes into plants. They can literally shoot new genes into plant cells using microscopic DNA-coated particles of gold or tungsten. Or they can use the microorganism Agrobacterium to install the genes for them. Not only can genetic engineers restore a plant’s original scent, they can give it the scent of another species. It’s a dizzying thought: roses that smell like violets, asters that smell like lilacs. The creation of transgenically fragrant flowers will be a victory for biotechnology and may ease public acceptance of biotech crops.
This would all seem like a perfect opportunity for the cut-flower industry. Yet Eran Pichersky tells me that producers are reluctant to make the effort. According to their market research, consumers claim that scent matters, but sales figures don’t reflect it. Consumer choice is driven by color and visual appeal. In any case, most flowers are bought as gifts, which means the purchaser doesn’t live with the scent, or lack thereof. Perhaps it is true, as Shakespeare said, that “to throw a perfume on the violet…Is wasteful and ridiculous excess.”
The Genes of Perception
Imagine a DNA test in which a marketer predicts your fragrance preferences in ten minutes using a drop of your saliva. Rapid, saliva-based clinical diagnostics like home pregnancy tests are already in use. Why shouldn’t there be point-of-sale diagnostics? Wouldn’t you trade a little spit to find your perfect fragrance?
The person-to-person variability in odor perception is enormous. To get an idea of the scale, compare it to color vision. Imagine that instead of three kinds of color blindness there were dozens, and that each type affected up to 75 percent of the population instead of only 6 percent. Smell scientists struggle to explain this variability; it remains one of the biggest mysteries