Abstract
Globe artichoke (Cynara cardunculus L. var. scolymus) is a rich source of compounds promoting human health (phytonutrients), among them caffeoylquinic acids (CQAs), mainly represented by chlorogenic acid (CGA), and dicaffeoylquinic acids (diCQAs). The enzymes involved in their biosynthesis belong to the large family of BAHD acyltransferases. Following a survey of the globe artichoke genome, we identified 69 BAHD proteins carrying the catalytic site (HXXXD). Their phylogenetic analysis together with another 43 proteins, from 21 species, representative of the BAHD family, highlighted their grouping in seven major clades. Nine globe artichoke acyltransferases clustered in a sub-group of Clade V, with 3 belonging to hydroxycinnamoyl-CoA:quinate hydroxycinnamoyl transferase (HQT) and 2 to hydroxycinnamoyl-CoA:shikimate/quinate hydroxycinnamoyl transferase (HCT) like proteins. We focused our attention on the former, HQT1, HQT2, and HQT3, as they are known to play a key role in CGA biosynthesis. The expression of genes coding for the three HQTs and correlation of expression with the CQA content is reported for different globe artichoke tissues. For the first time in the globe artichoke, we developed and applied the virus-induced gene silencing approach with the goal of assessing in vivo the effect of HQT1 silencing, which resulted in a marked reduction of both CGA and diCQAs. On the other hand, when the role of the three HQTs was assessed in leaves of Nicotiana benthamiana through their transient overexpression, significant increases in mono- and diCQAs content were observed. Using transient GFP fusion proteins expressed in N. benthamiana leaves we also established the sub-cellular localization of these three enzymes.
Highlights
Plant phenolics, and in particular the caffeoylquinic acids (CQAs), can synergistically or additively provide protection against damage induced by free radicals during oxidative stress, and reduce the risk of chronic diseases in humans (Arakawa et al, 2009; Puangpraphant et al, 2011; Markovic and Tošovic, 2016)
No globe artichoke BAHD proteins occurred in Clade IV which contained sequences related to barley agmatine coumaroyl transferase (ACT), an enzyme involved in the biosynthesis of anti-fungal hydroxycinnamoyl agmatine derivatives (Burhenne et al, 2003)
Clade V can be subdivided further into several subgroups, as reported in D’Auria (2006), three of which contained characterized enzymes: the first clustered three globe artichoke proteins along with enzymes that are involved in biosynthesis of volatile esters; the second grouped one globe artichoke protein with enzymes, from Taxus species, involved in the production of the compound paclitaxel; the third clustered nine globe artichoke sequences with enzymes that use hydroxycinnamoyl/benzoyl CoA as acyl donor
Summary
In particular the caffeoylquinic acids (CQAs), can synergistically or additively provide protection against damage induced by free radicals during oxidative stress, and reduce the risk of chronic diseases in humans (Arakawa et al, 2009; Puangpraphant et al, 2011; Markovic and Tošovic, 2016). Caffeoylquinic acids are produced as monoesters (monocaffeoylquinic acids, monoCQAs, which include chlorogenic acids, CGA) and diesters [dicaffeoylquinic acids, (diCQAs)] by members of plant families such as Asteraceae (a.k.a Compositae), Solanaceae, and Rubiaceae. Scolymus), a member of the Asteraceae family, has received renewed interest as a source of bioactive compounds (Lattanzio et al, 2009) due to its high content and diverse spectrum of phenolics. The health-promoting potential of globe artichoke extracts is supported by many in vivo and in vitro studies which demonstrate its hepatoprotective (Adzet et al, 1987), anticarcinogenic (Clifford, 2000), antioxidative (Gebhardt, 1997; Brown and Rice-Evans, 1998), antifungal and antibacterial properties (Gebhardt, 2001; Coon and Ernst, 2003; Lattanzio et al, 2009)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
