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

Yuting Wang,Yuan Yuan,Chao Wan,Binghua Wu,Meiling Lyu,Jinfeng Huang,Hongliang Zhang,Xian He

doi:10.3390/plants11010013

Yuting Wang, Yuan Yuan + Show 6 more

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https://doi.org/10.3390/plants11010013

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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.

Highlights

Plants utilize a wide array of specialized metabolites to interact with changing environments and to safeguard their survival and reproduction [1,2,3]
The peak-corresponding compounds were putatively identified based on the retention index (RI) (Kovats retention indices) and MS spectrum matching the NIST (National Institute of Standards and Technology) GC-MS databases (Figure S1), and authentic reference substance of α-farnesene, benzyl acetate, benzyl alcohol, and (R/S)linalool were used for the confirmation
Two highly expressed JsBEAT1 and JsBEAT2 were full-length cDNA cloned, and the encoded proteins could convert benzyl–alcohol to benzylacetate by using acetyl-CoA as the acyl donor in vitro

Summary

Introduction

Plants utilize a wide array of specialized metabolites to interact with changing environments and to safeguard their survival and reproduction [1,2,3]. These structurally different molecules produced by plants are usually classified based on their biosynthetic origin, such as terpenoids, benzenoids/phenylpropanoids, fatty acid derivatives and amino acid derivatives. Large portions of the plant-specialized metabolites are lipophilic small molecules with high vapor pressure at ambient temperatures, and called volatile organic compounds (VOCs). More than 1700 VOCs have been identified from 90 different plant families, and mostly are synthesized and released, with high abundance and diversity, from the flowers in many flowering plants [4].

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