Identification and Characterization of Five BAHD Acyltransferases Involved in Hydroxycinnamoyl Ester Metabolism in Chicory.

Guillaume Legrand,Marianne Delporte,Adeline Harant,Philippe Hance,David Gagneul,Monika Mörchen,Christophe Vuylsteker,Chahinez Khelifi,Jean-Louis Hilbert

doi:10.3389/fpls.2016.00741

Abstract

Chicory (Cichorium intybus) accumulates caffeic acid esters with important significance for human health. In this study, we aim at a better understanding of the biochemical pathway of these bioactive compounds. Detailed metabolic analysis reveals that C. intybus predominantly accumulates caftaric and chicoric acids in leaves, whereas isochlorogenic acid (3,5-diCQA) was almost exclusively accumulated in roots. Chlorogenic acid (3-CQA) was equally distributed in all organs. Interestingly, distribution of the four compounds was related to leaf age. Induction with methyljasmonate (MeJA) of root cell suspension cultures results in an increase of 3-CQA and 3,5-diCQA contents. Expressed sequence tag libraries were screened using members of the BAHD family identified in Arabidopsis and tobacco as baits. The full-length cDNAs of five genes were isolated. Predicted amino acid sequence analyses revealed typical features of BAHD family members. Biochemical characterization of the recombinant proteins expressed in Escherichia coli showed that two genes encode HCTs (hydroxycinnamoyl-CoA:shikimate/quinate hydroxycinnamoyltransferases, HCT1 and HCT2) whereas, three genes encode HQTs (hydroxycinnamoyl-CoA:quinate hydroxycinnamoyltransferases, HQT1, HQT2, and HQT3). These results totally agreed with the phylogenetic analysis done with the predicted amino acid sequences. Quantitative real-time polymerase chain reaction analysis of gene expression indicated that HQT3, HCT1, and HCT2 might be more directly associated with CQA accumulation in cell culture in response to MeJA elicitation. Transient expression of HCT1 and HQT1 in tobacco resulted in a higher production of 3-CQA. All together these data confirm the involvement of functionally redundant genes in 3-CQA and related compound synthesis in the Asteraceae family.

Highlights

Plants accumulate a wide range of specialized metabolites with a large diversity of chemical types
Detailed analyses show that chicory predominantly accumulates one of the CQA isomers, 3-CQA, and 3,5-diCQA one of the diCQA isomers
An additional CQA isomer, i.e., 5-CQA known as neochlorogenic acid was detected in root tissues

Summary

Introduction

Plants accumulate a wide range of specialized metabolites with a large diversity of chemical types. Phenolic compounds are recognized for their health benefit effects and are the most important dietary antioxidants. Chicory (Cichorium intybus L.) is a member of the Asteraceae family used for a long time in traditional medicine This is notably due to the accumulation of high-value health promoting compounds such as CQA, diCQA, CTA, and diCTA (Kandeler and Ullrich, 2009; Bahri et al, 2012). Many health benefit effects are attributed to these molecules when isolated (Tousch et al, 2008; Koriem and Soliman, 2014; Yasir et al, 2016) In addition to their notable dietary role, these molecules are important compounds with multiple roles in plants. CQA as well as feruloylquinate were identified as protective agents against thrips in chrysanthemum (Dendranthema grandiflora; Leiss et al, 2009)

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