Unexpected enzyme may resurrect roses' fading scents

These ornamental plants, which provide essential oils for perfumes and cosmetics, have been bred mostly for their visual traits, and their once-strong scents have faded over the generations. Restoring their fragrant odors will require a better understanding of the rose scent biosynthesis pathway.

Until now, most studies of rose fragrance have focused on a biosynthetic pathway that generates pleasant-smelling alcohols, known as monoterpenes, using specific enzymes called terpene synthases. Some scientists have argued that terpene synthases are the sole route to the production of fragrant monoterpenes in plants.

However, by investigating the genes of two rose cultivars selected for certain desirable characteristics, Jean-Louis Magnard and colleagues discovered that the flowers' fragrances were facilitated by a completely unexpected family of enzymes.

Specifically, the researchers compared the transcriptomes of the Papa Meilland cultivar, which smells very strongly, and the Rogue Meilland cultivar, which produces very little scent, to flesh out their genetic differences. They found that the RhNUDX1 enzyme, which acts in the cytoplasm of cells located in the flowers' petals, generates the fragrant and well-known monoterpene geraniol, the primary part of rose oil.

In the future, botanists might be able to exploit the RhNUDX1 gene in order to breed appealing scents back into these iconic flowers, they say. A Perspective by Dorothea Tholl and Jonathan Gershenzon explains the study in greater detail.