Floral scent emission of Epiphyllum oxypetalum: discovery of its cytosol-localized geraniol biosynthesis

Abstract

Epiphyllum oxypetalum, a renowned ornamental species in Cactaceae, releases attractive fragrance during its infrequent, transient, and nocturnal blooms. However, the floral fragrance composition and biosynthesis remain largely unexplored. Employing volatilomics, transcriptomics, and biochemistry, we systematically characterized the composition, emission dynamics, and biosynthesis of the floral scent of E. oxypetalum. The floral scent composition of E. oxypetalum was highly dynamic. Starting after 8 p.m. local time, volatile emission increased 200-fold within 6 h. At full bloom, geraniol accounted for 72.54% of the total emission, followed by benzyl alcohol (12.96%) and methyl salicylate (3.75%). These scents predominantly originated from petals and sepals. Transcriptomic analysis and inhibition assays using pathway-specific inhibitors revealed that the mevalonate pathway was the precursor source for geraniol biosynthesis. Functionally characterized cytosol-localized geraniol synthase EoTPSa1 was the key enzyme responsible for geraniol biosynthesis. Together, these findings pinpoint a cytosolic biosynthetic route for the major scent volatile geraniol in E. oxypetalum. Our study provides new insights into the emission dynamics and biosynthesis of E. oxypetalum floral scents. In particular, we demonstrate a distinctive mevalonate pathway-based geraniol biosynthetic pathway, which may hold potential for the development of novel perfume products.

Acknowledgements

We thank Yudong Ma, Rao Wu, and Jin Dai for their assistance in sample collection, and Bolei Jiao, Xinrui Liu, and Chuanfang Wu for sharing the N. benthamiana plants and pSuper1300 and pET-28a plastids. We further wish to thank Qijun Deng and Wei Ni from Sichuan Bowu Cultural Development Co. Ltd. for drawing the E. oxypetalum flowers.

Financial support was provided by the National Science and Technology Major Project (20250065)， the National Nature Science Foundation of China (32271692, 32470009, 32100326,), and the Department of Science and Technology of Sichuan Province of China (2022ZHXC0009, 2022NSFSC0158, 2023YFSY0054).

Author Contributions

Y.Y.Z., Y.H.Z, L.T., and Q.S. designed the experiments. The top eight authors and W.T. jointly completed the collection and preparation of samples. Y.Y.Z. and Y.H.Z. quantified the VOC content via GC-MS. Y.Y.Z. analysed the GC-MS and transcriptome data. Y.Y.Z., Y.H.Z., A.D.Z, B.Y., and Q.R.T. performed the molecular cloning, enzymatic assays, and localization studies. L.K.W. performed the biochemical quantifications. Y.Y.Z. plotted the figures and wrote the first draft. Y.Y.Z., Y.H.Z., Q.S., T.L., H.J.X., Q.R.T., M.C.L., and Z.B.L. revised the manuscript. Y.Y.Z. and Y.H.Z. should be considered the joint first authors, whereas Q.S. and T.L. the joint corresponding authors.

Data availability

All the data needed to evaluate the conclusions in the paper are presented in the paper and/or the Supplementary Materials. The raw transcriptome reads for the nine individuals in this study have been deposited in the National Genomics Data Center (https://ngdc.cncb.ac.cn) under accession number PRJCA024038.

Conflict of interests

The authors declare that they have no conflicts of interest.

Supplementary Data

Supplementary data is available at Horticulture Research online.

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