When wine lovers swirl a glass of pinot noir, they toss out words like "prune," "smoke," and "leather"--hardly scientific. Now, researchers are a step closer to understanding the genetic basis for such fruity terms. A consortium of French and Italian researchers has sequenced the genome of the pinot noir grapevine. The results also provide clues to the evolution of flowering plants.
Wine is a complex beverage, and not just for the palate. Researchers want to sort out the molecular components because they not only contribute to taste and aroma but also improve health. Several groups are trying to sequence varietals such as Syrah and Cabernet Sauvignon. But the two copies of chromosomes in grape plants are generally quite different from each other, making sequencing difficult--it's like decoding two genomes instead of just one.
To get around this obstacle, a group led by Patrick Wincker of the Université d'Evry in France used a variety of pinot noir that had been bred so that the chromosomes share 93% of their sequence. The team deciphered approximately 61% of the genome of this variety, called PN40024.
The genome reveals part of the basis for wine's complexity, the scientists report online today in Nature. Genes for polyphenols, which are typically involved in flavor, color, and aroma, belonged to families much larger than those in nongrapevine species. For example, the vine's turpene synthase family, which contributes to wine's bouquet, includes almost 90 genes, nearly triple the number found in the mustard Arabidopsis. The PN40024 plants also carried 43 genes related to resveratrol, which not only adds bitterness and astringency but also prolongs the life of mice and other lab animals (ScienceNOW, 14 July 2004).
In addition, the team lined up similar groups of genes within the chromosomes and found what appeared to be three complete genomes, suggesting a triplication event in the distant past. Wincker says this "paleohexaploidization" predates the time when other flowering plants such as Arabidopsis and poplar split from the grapevine.
"The work provides us with a foundation for doing studies that will tell us more about ripening, fruit composition, and wine quality," says plant physiologist Gregory Gambetta of the University of California, Davis. UC Davis enologist Susan Ebeler adds that the results will help researchers understand how the environment can be used to influence wine composition.
But not everyone is convinced the sequence accurately captures the luscious varietal's essence. Geneticist Riccardo Velasco of the Istituto Agrario di San Michele all'Adige in Italy, who heads a second group that is sequencing the pinot noir genome, argues that because of its hybrid origin, PN40024 is only 50% pinot noir. "Its purity doesn't resemble the pinot noir genome," Velasco says. "The cultivar has never produced wine."
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