Roses’ Sweet Fragrance Traced to Molecular Pathway by Researchers

An international team of botanists, plant biologists and biochemists has found a crucial pathway that roses use to produce their familiar sweet scent. In their study, it was reported in Proceedings of the National Academy of Sciencesthe group traced the pathway that allows binding molecules to produce the chemicals needed to create the scent associated with roses.

Roses have been a favorite flower for many years, and horticulturists have worked to improve aspects that are preferred by consumers, creating varieties of roses that last longer in a vase, for example, or that have unnatural colors. An unfortunate side effect of flowering roses is the gradual loss of their unique aromatic fragrance. In this new effort, the research team sought to learn more about the process involved in producing and possibly restoring the sweet scent of roses in a hybrid flowering.

Previous research has shown that a chemical called geraniol makes roses smell the way they do. Rose plants make the chemical using a reaction that involves an enzyme called farnesyl diphosphate (FPP) and other enzymes including NUDX1 hydrolase, which is produced inside plant cells. It also contains the cytosol, which is found in flower petals.

To create enough geranol, plants need to produce lots of the enzyme NUDX1 hydrolase, which can only happen if there are lots of binding molecules called geranyl diphosphate (GPP). Thus, for the rose to generate plenty of sweet-smelling geranols, the two main substances included in its composition had to be created in close proximity to each other—but that wasn’t the case when the researchers looked at where they were created. This indicates that there is a missing path between them.

To find this pathway, the team chose one specific plant, called Old Blush—a pink rose with a lovely scent. They closed off potential pathways in different plants and then watched to see how much geraniol they managed to produce. They isolated a pathway in the plant cytosol, and found that it played a second role — it created GPP-binding compounds that, along with GPP itself, allowed the production of geraniol.

To test their findings, they engineered a tobacco plant to express FPP, and found that it led to the production of both enzymes, proving their theory. The group concluded that engineering hybrid roses in similar ways could restore their famous scent.

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