Characterization of Two BAHD Acetyltransferases Highly Expressed in the Flowers of Jasminum sambac (L.) Aiton

Abstract

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 Km of 447.3 μM for benzylalcohol and 546.0 μM for acetate-CoA, whereas in the instance of the His-JsBEAT2, the Km 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 kcat 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.

Multiomics Analysis Reveals the Involvement of JsLHY in Controlling Aroma Production in Jasmine Flowers

“…Although several studies have identified many structural genes involved in the biosynthesis of floral VOCs during jasmine flowering, however, to the best of our knowledge, the regulation of TFs during the formation of jasmine floral aromas has not been confirmed thus far. , In this study, we focused on the identification of potential TFs mediating key odorant biosynthesis and used JsLHY as an entry point to investigate the mechanism underlying how JsLHY regulates the aroma formation of jasmine.…”

“…27 The JsActin2 was used as an internal reference. 14,15,28 The relative expression levels were calculated using the 2 −ΔΔCT method. 29 If not specified, all sequences of primers used in this study are listed in Table S2.…”

“…The qRT–PCR assay was performed on the DLAB Accurate 96 (DLAB Scientific Co., Ltd., Beijing, China) platform with the conditions and reaction mixture described previously . The JsActin2 was used as an internal reference. ,, The relative expression levels were calculated using the 2 –ΔΔCT method . If not specified, all sequences of primers used in this study are listed in Table S2.…”

“…The jasmine flower [ Jasminum sambac (L.) Aiton] is famous for its rich and elegant aroma and is an important raw material for producing jasmine tea and essential oils with high commercial value. , Its aromatic VOCs, including VTs, VPBs, and FADVs, are almost simultaneously synthesized and released during jasmine flower opening at night followed by rapid fading for approximately 1 day. − Due to the late start of molecular biology research on jasmine, our knowledge of the regulatory mechanisms of the biosynthesis of VOCs has not yet been explicit. Thus, only by a full understanding of the molecular mechanism of aroma formation in jasmine can the fragrance release process be effectively regulated to improve aroma utilization.…”

“…Thus, only by a full understanding of the molecular mechanism of aroma formation in jasmine can the fragrance release process be effectively regulated to improve aroma utilization. With the completion of genome sequencing of jasmine, a large set of aroma-related structural genes were identified at the whole-genome scale. − Previous studies have revealed that many structural genes are involved in the biosynthesis of VT, VPB, and FADVs during jasmine flower opening. − , These studies laid a foundation for exploring the regulatory mechanisms of jasmine aroma formation. As the mechanisms underlying aroma formation rely on the orchestration of related TFs, which TFs induce the expression of structural genes and promote the synthesis of VOCs within the same time frame in jasmine is an urgent question to be addressed.…”