Enzyme behind sweet scent of roses found

Researchers have identified an enzyme which plays a key role in producing the sweet fragrances in roses, a finding that can help restore a pleasing scent to rose varieties that have lost it.
Roses, 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, researchers said.
Restoring their fragrant odours will require a better understanding of the rose scent biosynthesis pathway, they said.
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 from The University of Lyon Saint-Etienne, France, 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, researchers said.