Abstract
The market demand for essential oil containing citral is increasing. Our research group identified a rare chemotype of Camphora officinarum whose leaves are high in citral content by examining over 1000 wild trees across the entire native distribution area of C. officinarum in China. Because C. officinarum is suitable for large-scale cultivation, it is therefore seen as a promising source of natural citral. However, the molecular mechanism of citral biosynthesis in C. officinarum is poorly understood. In this study, transcriptomic analyses of C. officinarum with different citral contents revealed a strong positive correlation between the expression of a putative geraniol synthase gene (CoGES) and citral content. The CoGES cDNA was cloned, and the CoGES protein shared high similarity with other monoterpene synthases. Enzymatic assays of CoGES with geranyl diphosphate (GPP) as substrate yielded geraniol as the single product, which is the precursor of citral. Further transient expression of CoGES in Nicotiana benthamiana resulted in a higher relative content of geranial and the appearance of a new substance, neral. These findings indicate that CoGES is a geraniol synthase-encoding gene, and the encoded protein can catalyze the transformation of GPP into geraniol, which is further converted into geranial and neral through an unknown mechanism in vivo. These findings expand our understanding of citral biosynthesis in Lauraceae plants.
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Funding was provided by Jiangxi Provincial Department of Science and Technology (Grant No. 20212BAB215025, 20203ABC28W016, 20204BCJL23046, 20181ACF60002).
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Conceptualization, Jiexi Hou, Haiyan Zhang, and Zhinong **; methodology, Jiexi Hou, Yuzhou Wu, Lei Lei, Yanbo Wang, and Qingyan Ling; software, Jiexi Hou and Yuzhou Wu; validation, Lei Lei and Yanbo Wang; formal analysis, Yuzhou Wu, Jiexi Hou, and Qingyan Ling; investigation, Jiexi Hou and Lei Lei; resources, Jie Zhang and Jiao Zhao; data curation, Jiexi Hou and Haiyan Zhang; writing—original draft preparation, Jiexi Hou; writing—review and editing, Yuzhou Wu and Haiyan Zhang; supervision, Haiyan Zhang and Zhinong **; project administration, Lei Lei, Jie Zhang, and Jiao Zhao; funding acquisition, Jiexi Hou, Zhinong **, Jie Zhang, and Jiao Zhao. All authors have read and agreed to the published version of the manuscript.
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Hou, J., Wu, Y., Lei, L. et al. Identification and functional analysis of a deduced geraniol synthase from Camphora officinarum. Physiol Mol Biol Plants 30, 867–876 (2024). https://doi.org/10.1007/s12298-024-01463-4
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DOI: https://doi.org/10.1007/s12298-024-01463-4