Identification of putative acyltransferase genes responsible for the biosynthesis of homogenous and heterogenous hydroxycinnamoyl-tartaric acid esters from Bidens pilosa

Abstract

Bidens pilosa is an edible plant with highly sought-after nutraceutical properties. The purported bioactivities of this plant can be correlated to the high number of metabolites. Amongst these metabolites, different derivatives of hydroxy‑cinnamoyl esters have been shown to exist in high proportions. However, the enzymatic machinery, thus the biosynthetic pathways responsible for the accumulation of these compounds in the plant have not yet been identified. For the first time, we report the putative identification of two genes with sequence homology to hydroxycinnamoyl-CoA: tartaric acid hydroxycinnamoyl transferase (HTT) in B. pilosa. The full-length sequence of the two isoforms of the HTT gene was achieved using single-molecule real-time (SMRT) sequencing approach. Analyses of methanolic extracts of B. pilosa through Liquid-chromatography hyphenated with mass spectrometry (LC-MS) technique revealed the existence of heterogeneous hydroxycinnamoyl-tartaric acid esters consisting of different hydroxycinnamoyl derivatives. To the best of our knowledge, this is a first report on these molecules from B. pilosa. Taken altogether, this plant utilises hydroxycinnamoyl-CoA tartaric hydroxycinnamoyl transferase (HTT) genes to diversify its metabolite composition through esterification of tartaric acid acceptor molecule by acylating it with either homogeneous or heterogenous hydroxycinnamic acids (HCA) derivatives. Therefore, B. pilosa is a source of structurally diverse isomeric compounds with purported nutraceutical values. The enzyme products of the two identified HTT genes are therefore pointed out as possible catalysts which can be further exploited by incorporating them in other economically viable plants to enhance the nutraceutical values thereof.