Abstract
Clematisflorida is a popular ornamental vine species known for diverse colors and shapes of its flowers but not for scent. Here we investigated the composition and biosynthesis of floral scent in ‘Kaiser’, a fragrant cultivar of C. florida that has sterile flowers. Volatile profiling revealed that flowers of ‘Kaiser’ emit more than 20 compounds, with monoterpenes being most abundant. Among the three floral organs, namely sepals, transformed-petals, and ovaries, ovaries had the highest rates of total volatile emission. To determine the molecular mechanism underlying floral scent biosynthesis in ‘Kaiser’, we sequenced a flower transcriptome and searched the transcriptome for terpene synthase genes (TPSs), which are key genes for terpene biosynthesis. Among the TPS genes identified, three were putative intact full-length genes and were designated CfTPS1, CfTPS2, and CfTPS3. Phylogenetic analysis placed CfTPS1, CfTPS2, and CfTPS3 to the TPS-g, TPS-b, and TPS-a subfamily, respectively. Through in vitro enzyme assays with Escherichia coli-expressed recombinant proteins, both CfTPS1 and CfTPS2 were demonstrated to catalyze the conversion of geranyl diphosphate to linalool, the most abundant constituent of C. florida floral scent. In addition, CfTPS1 and CfTPS2 produced the sesquiterpene nerolidol from (E,E)-farnesyl diphosphate. CfTPS3 showed sesquiterpene synthase activity and produced multiple products in vitro. All three CfTPS genes showed higher levels of expression in sepals than those in transformed-petals and ovaries. Our results show that despite being sterile, the flowers of ‘Kaiser’ have normal mechanisms for floral scent biosynthesis that make the flowers fragrant.
Highlights
Among the most popular perennial climbing ornamental species is Clematis florida, which belongs to the Ranunculaceae family
We investigated the chemical composition and biosynthesis of floral scent of ‘Kaiser’, In this study, we investigated the chemical composition and biosynthesis of floral scent of a fragrant cultivar of C. florida
In terms of emission rates floral organs, it was somehow surprising that ovaries of ‘Kaiser’ flowers exhibited the highest rates of of different floral organs, it was somehow surprising that ovaries of ‘Kaiser’ flowers exhibited the total emission among the three floral organs examined (Figure 2)
Summary
Among the most popular perennial climbing ornamental species is Clematis florida, which belongs to the Ranunculaceae family. A large number of cultivars have been developed for. They are widely used in landscaping and floriculture as garden or potted plants [1]. The predominant morphological features of the hermaphrodite flower of C. flrodia are their diverse colors and shapes. Aside from ornamental applications, the roots and rhizomes of C. florida have been used as anti-inflammatory, anti-rheumatism, and analgesic agents [2] due to the richness in secondary. Among the traits that make C. florida a popular ornamental plant, the floral scent is usually not one of them. New varieties with fragrant flowers in addition to other attractive horticultural traits are important targets for new breeding programs of
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