AUTHOR=Yue Yuechong , Wang Lan , Yu Rangcai , Chen Feng , He Jieling , Li Xinyue , Yu Yunyi , Fan Yanping 

TITLE=Coordinated and High-Level Expression of Biosynthetic Pathway Genes Is Responsible for the Production of a Major Floral Scent Compound Methyl Benzoate in Hedychium coronarium

JOURNAL=Frontiers in Plant Science

VOLUME=12

YEAR=2021

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2021.650582

DOI=10.3389/fpls.2021.650582

ISSN=1664-462X

ABSTRACT=<p>Methyl benzoate is a constituent of floral scent profile of many flowering plants. However, its biosynthesis, particularly in monocots, is scarcely reported. The monocot <italic>Hedychium coronarium</italic> is a popular ornamental plant in tropical and subtropical regions partly for its intense and inviting fragrance, which is mainly determined by methyl benzoate and monoterpenes. Interestingly, several related <italic>Hedychium</italic> species lack floral scent. Here, we studied the molecular mechanism of methyl benzoate biosynthesis in <italic>H. coronarium</italic>. The emission of methyl benzoate in <italic>H. coronarium</italic> was found to be flower-specific and developmentally regulated. As such, seven candidate genes associated with methyl benzoate biosynthesis were identified from flower transcriptome of <italic>H. coronarium</italic> and isolated. Among them, HcBSMT1 and HcBSMT2 were demonstrated to catalyze the methylation of benzoic acid and salicylic acid to form methyl benzoate and methyl salicylate, respectively. Methyl salicylate is a minor constituent of <italic>H. coronarium</italic> floral scent. Kinetic analysis revealed that HcBSMT2 exhibits a 16.6-fold lower <italic>K</italic>m value for benzoic acid than HcBSMT1, indicating its dominant role for floral methyl benzoate formation. The seven genes associated with methyl benzoate biosynthesis exhibited flower-specific or flower-preferential expression that was developmentally regulated. The gene expression and correlation analysis suggests that <italic>HcCNL</italic> and <italic>HcBSMT2</italic> play critical roles in the regulation of methyl benzoate biosynthesis. Comparison of emission and gene expression among four <italic>Hedychium</italic> species suggested that coordinated and high-level expression of biosynthetic pathway genes is responsible for the massive emission of floral methyl benzoate in <italic>H. coronarium</italic>. Our results provide new insights into the molecular mechanism for methyl benzoate biosynthesis in monocots and identify useful molecular targets for genetic modification of scent-related traits in <italic>Hedychium</italic>.</p>