Floral scent is built from volatile organic compounds (VOCs), among which terpenes form one of the largest and most diverse groups. These molecules are produced through branching metabolic routes and are shaped by enzymes that supply precursors, build terpene skeletons, or generate alcohol-type volatiles through alternative reactions. In ornamental species, however, many fragrance traits are still difficult to breed because the responsible genes and enzymes are not fully known. In herbaceous peony, previous studies had identified several terpene synthase genes, but the wider enzymatic network remained unclear. Based on these challenges, there is a need to conduct in-depth research into the genetic and biochemical routes controlling peony floral scent.
Researchers from the Agricultural Genomics Institute at Shenzhen, Chinese Academy of Agricultural Sciences; Northeast Normal University; and Karatina University reported (DOI: 10.1093/hr/uhag091) the study in Horticulture Research on 9 March 2026. Using P. lactiflora ‘Zifengyu’ as a fragrance-rich model, the team examined how terpene synthase (TPS), Nudix hydrolase (NUDX), and prenyltransferase (PT) enzymes jointly shape terpene biosynthesis during flower development. The work identified dominant scent compounds, tested candidate enzymes in vitro and in planta, and mapped how cellular location helps determine whether enzymes produce monoterpenes or sesquiterpenes.
The team first profiled flower volatiles across bud, half-open, and fully open stages, as well as in sepals, stamens, petals, and carpels. Total terpene emission increased as flowers opened, driven largely by monoterpenes. β-caryophyllene was prominent early and peaked at the half-open stage, while geraniol, citronellol, and 1,8-cineole became abundant in mature floral tissues, especially stamens and petals. Functional screening then identified 12 PlTPS genes, nine of which showed catalytic activity. The PlTPS4 protein produced β-caryophyllene, PlTPS5 produced 1,8-cineole, and PlTPS9 generated geraniol. Mutation tests showed that specific amino acid residues were essential for PlTPS4 and PlTPS5 activity, linking small protein changes to scent diversity. The PlNUDX protein added another route by hydrolyzing geranyl diphosphate (GPP) and neryl diphosphate (NPP) to support geraniol and nerol production. PT enzymes supplied key precursors, including farnesyl diphosphate (FPP) and GPP, completing a compartmentalized model of peony terpene biosynthesis.
The authors said the study shows that peony fragrance is not controlled by a single “scent gene,” but by a flexible metabolic network. They said the discovery of both TPS-dependent and NUDX-mediated routes helps explain how flowers generate a layered scent profile during opening. They also emphasized that enzyme location matters: plastid-localized proteins mainly support monoterpene production, while cytosolic proteins favor sesquiterpene formation. This cellular separation gives breeders and biologists a clearer map for understanding why different peony cultivars smell different.
These findings provide practical genetic targets for improving fragrance in ornamental breeding. Candidate genes such as PlTPS4, PlTPS5, PlTPS9, and PlNUDX may help guide future efforts to enhance β-caryophyllene, 1,8-cineole, geraniol, or related scent notes in peony and potentially other ornamental crops. The study also highlights that modifying precursor supply through PT enzymes could reshape volatile output, offering a broader strategy than targeting terpene synthases alone. In the long term, this work may support fragrance-oriented cultivar development, essential oil research, and more precise molecular breeding of flowers with richer and more stable scent profiles.
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References
DOI
10.1093/hr/uhag091
Original Source URL
https://doi.org/10.1093/hr/uhag091
Funding information
This work was supported by the National Natural Science Foundation of China, the Shenzhen Fundamental Research Program, the Chinese Academy of Agricultural Sciences Elite Youth Program, and the Fundamental Research Funds for the Central Universities.
About Horticulture Research
Horticulture Research is an open access journal of Nanjing Agricultural University and ranked number one in the Horticulture category of the Journal Citation Reports ™ from Clarivate, 2023. The journal is committed to publishing original research articles, reviews, perspectives, comments, correspondence articles and letters to the editor related to all major horticultural plants and disciplines, including biotechnology, breeding, cellular and molecular biology, evolution, genetics, inter-species interactions, physiology, and the origination and domestication of crops.