Volatile benzenoid compounds are found in diverse aromatic bouquets emitted by most moth-pollinated flowers. The night-blooming Jasminum sambac is widely cultivated worldwide in the tropics and subtropics for ornamental and industrial purposes owing to its fragrant flowers. Benzylacetate is a characteristic constituent in jasmine scent which makes up to approximately 20–30% of the total emission in the headspace or extract, but the biosynthesis enzymes and the encoding genes have not yet been described. Here, we identify two cytosolic BAHD acyltransferases specifically expressed in the petals with a positive correlation closely to the emission pattern of the volatile benzenoids. Both JsBEAT1 and JsBEAT2 could use benzylalcohol and acetate-CoA as substrates to make benzylacetate in vitro. The recombinant GST-JsBEAT1 has an estimated apparent K_m of 447.3 μM for benzylalcohol and 546.0 μM for acetate-CoA, whereas in the instance of the His-JsBEAT2, the K_m values are marginally lower, being 278.7 and 317.3 μM, respectively. However, the catalytic reactions by the GST-JsBEAT1 are more efficient than that by the His-JsBEAT2, based on the steady-state k_cat parameters. Furthermore, ectopic expression of JsBEAT1 and JsBEAT2 in the transgenic P. hybrida plants, driven by a flower-specific promotor, significantly enhances the biosynthesis of benzylbenzoate and benzylacetate, as well as the total VOCs.

Floral volatile terpenoids are known to play important roles in plant pollination biology by attracting animal pollinators and repelling antagonists, as well as enhancing resistance to potential microbial pathogens. Terpenoid blend emitted by a flower is usually plant-lineage specific and mostly determined by a set of versatile terpene synthases (TPSs) which catalyze the final step of diverse terpenoid synthesis. The strongly scented flower of Jasminum sambac emits linalool and α-farnesene dominating the nocturnal floral VOC, yet the corresponding TPSs have not been identified. Here, we show that four TPS enzymes are responsible for the synthesis of the mixtures of volatile terpenoids in the flower, based on their highly-correlated and almost-exclusive expression in the petal, and on their enzymatic characterizations in vitro and in Nicotiana benthamiana. JsTPS01 (TPS-a) acts as a sesquiterpene synthase, producing τ-cadinol in yeast at levels that mirror its rhythmic expression in petals. JsTPS02 (TPS-b) carries a plastid-transit peptide, localizes to chloroplasts/plastids, and converts GPP to linalool with high affinity (Km = 28.2 ± 3.4 µM). JsTPS03 is a TPS-b clade member that is able to convert FPP to farnesol with a Km of 14.4 ± 5.9 μM in an in vitro assay using isolated yeast vehicles. JsTPS04 (TPS-e/f) exhibits dual targeting—cytosolic in Arabidopsis protoplasts but plastidic in J. sambac petals—and functions as a bifunctional mono-/sesqui-TPS, forming linalool from GPP (Km = 2.5 ± 0.3 µM) and trans-nerolidol from FPP (Km = 7.6 ± 0.6 µM). Transient expression in Nicotiana benthamiana leaves further confirmed its in-planta linalool production. collectively, we identified four preferentially expressed terpene synthases contribute to linalool, τ-cadinol, tans-nerolidol, and farnesol in Jasminum sambac.

Floral volatile terpenoids are known to play important roles in plant pollination biology by attracting animal pollinators, repelling antagonists, and enhancing resistance to potential microbial pathogens. The terpenoid blend emitted by a flower is usually plant-lineage specific and is primarily determined by a set of versatile terpene synthases (TPSs), which catalyze the final step of diverse terpenoid synthesis. The strongly scented flower of Jasminum sambac (L.) Aiton emits linalool and α-farnesene, which dominate the nocturnal floral VOCs, yet the corresponding TPSs have not been identified. Here, we show that four TPS enzymes are responsible for the synthesis of a mixture of volatile terpenoids in the flower, based on their highly correlated and almost exclusive expression in the petal, as well as their enzymatic characterizations in vitro and in Nicotiana benthamiana Domin. JsTPS01 (TPS-a) acts as a sesquiterpene synthase, producing τ-cadinol in yeast at levels that mirror its rhythmic expression in petals. JsTPS02 (TPS-b) carries a plastid-targeting transit peptide, localizes to chloroplasts/plastids, and converts geranyl diphosphate (GPP) to linalool with high affinity (K_m = 28.2 ± 3.4 µM). JsTPS03 is a TPS-b clade member that can convert farnesyl diphosphate (FPP) to farnesol with a K_m of 14.4 ± 5.9 μM in an in vitro assay using isolated yeast vehicles. JsTPS04 (TPS-e/f) exhibits dual targeting—cytosolic in protoplasts of Arabidopsis thaliana (L.) Heynh, but plastidic in J. sambac petals—and functions as a bifunctional mono-/sesqui-TPS, forming linalool from GPP (K_m = 2.5 ± 0.3 µM) and trans-nerolidol from FPP (K_m = 7.6 ± 0.6 µM). Transient expression in N. benthamiana leaves further confirmed its in-planta linalool production. Collectively, we identified four preferentially expressed terpene synthases that contribute to the production of linalool, τ-cadinol, trans-nerolidol, and farnesol in J. sambac.