Metabolomics-guided investigations of unintended effects of the expression of the hydroxycinnamoyl quinate hydroxycinnamoyltransferase (hqt1) gene from Cynara cardunculus var. scolymus in Nicotiana tabacum cell cultures

• Published in: Plant physiology and biochemistry Vol. 127; pp. 287 - 298
• Main Authors: Mudau, S.P., Steenkamp, P.A., Piater, L.A., De Palma, M., Tucci, M., Madala, N.E., Dubery, I.A.
• Format: Journal Article
• Language: English
• Published: France Elsevier Masson SAS 01.06.2018
• Subjects: abscisic acid; Acyltransferases - genetics; Acyltransferases - metabolism; artichokes; Benzoic acid; Cell culture; chemometrics; chlorogenic acid; Chlorogenic acids; Cynara - enzymology; Cynara - genetics; Cynara cardunculus subsp. cardunculus; discriminant analysis; gene overexpression; high performance liquid chromatography; Hqt gene; Hydroxycinnamoyltransferase; least squares; leaves; mass spectrometry; metabolome; Metabolomics; Metabolomics profiling; Nicotiana - cytology; Nicotiana - genetics; Nicotiana - metabolism; Nicotiana tabacum; phenolic compounds; Phenylpropanoid pathway; Plant Cells - metabolism; Plant Proteins - genetics; Plant Proteins - metabolism; principal component analysis; tissues; tobacco; transgenes; transgenic plants; ultra-performance liquid chromatography; Benzoic acid; Hqt gene; Cell culture; Phenylpropanoid pathway; Chlorogenic acids; Metabolomics profiling; Hydroxycinnamoyltransferase
• ISSN: 0981-9428; 1873-2690; 1873-2690
• DOI: 10.1016/j.plaphy.2018.04.005

Chlorogenic acids (CGAs) are phenolic compounds biosynthesized in the phenylpropanoid pathway, with hydroxycinnamoyl quinate hydroxycinnamoyltransferase (HQT) as the key enzyme. Variation of CGAs has been noted in different plants, with globe artichoke (Cynara cardunculus var. scolymus L.) producing high amounts and a diverse spectrum of CGAs in its leaves. In the current study, the effect of overexpression of the hqt1 transgene from globe artichoke in tobacco was evaluated at the metabolome level. Here, metabolomic approaches based on ultra-high performance liquid chromatography coupled to mass spectrometry, together with chemometric models such as principal component analysis and orthogonal partial least square discriminant analysis, were employed to evaluate altered metabolic changes due to hqt1 overexpression. CGA profiles (caffeoylquinic acids: 3-CQA, 4-CQA and 5-CQA; p-coumaroylquinic acids: 4-pCoQA and 5-pCoQA; and 4,5-di-caffeoylquinic acid) of transgenic tobacco cell cultures were detected at lower concentrations than in the wild type. Interestingly, the cells were found to rather accumulate, as an unintended effect, abscisic acid - and benzoic acid derivatives. The results suggest that insertion of hqt1 in tobacco, and overexpression in undifferentiated cells, led to rechannelling of the phenylpropanoid pathway to accumulate benzoic acids. These findings proved to be contrary to the results shown elsewhere in leaf tissues, thus indicating differential metabolic control and regulation in the undifferentiated cell culture system. •Hydroxycinnamoyl quinate hydroxycinnamoyltransferase synthesizes chlorogenic acids.•Metabolomic profiling of tobacco cells expressing hqt1 from artichoke was conducted.•Altered metabolic changes due to hqt1 overexpression were evaluated.•Biosynthesis of chlorogenic acids was significantly down-regulated.•Rechannelling of the phenylpropanoid pathway led to accumulation of benzoic acids.