Abstract
Chlorogenic acid and its derivatives (CQAs) are considered as important bioactive secondary metabolites in Gardenia jasminoides Ellis (G. jasminoides). However, few studies have investigated the biosynthesis and regulation of CQAs in G. jasminoides. In this study, methyl jasmonate (MeJA) was used to enhance CQAs accumulation in cultured G. jasminoides cells. Moreover, the possible molecular mechanism of MeJA-mediated accumulation of CQAs is also explored. To this end, time-course transcriptional profiles of G. jasminoides cells responding to MeJA were used to investigate the mechanism from different aspects, including jasmonate (JAs) biosynthesis, signal transduction, biosynthesis of precursor, CQAs biosynthesis, transporters, and transcription factors (TFs). A total of 57,069 unigenes were assembled from the clean reads, in which 80.7% unigenes were successfully annotated. Furthermore, comparative transcriptomic results indicated that differentially expressed genes (DEGs) were mainly involved in JAs biosynthesis and signal transduction (25 DEGs), biosynthesis of precursor for CQAs (18 DEGs), CQAs biosynthesis (19 DEGs), and transporters (29 DEGs). Most of these DEGs showed continuously upregulated expressions over time, which might activate the jasmonic acid (JA) signal transduction network, boost precursor supply, and ultimately stimulate CQAs biosynthesis. Additionally, various TFs from different TF families also responded to MeJA elicitation. Interestingly, 38 DEGs from different subgroups of the MYB family might display positive or negative regulations on phenylpropanoids, especially on CQAs biosynthesis. Conclusively, our results provide insight into the possible molecular mechanism of regulation on CQAs biosynthesis, which led to a high CQAs yield in the G. jasminoides cells under MeJA treatment.
Highlights
Gardenia jasminoides Ellis (G. jasminoides) is an evergreen shrub of family Rubiaceae, which is widely distributed in Southern China
These chlorogenic acid and its derivatives (CQAs) remained in relatively high concentrations until the 72nd hour of elicitation, the maximum of which was 21.7 times (26.26 mg g−1) more than that of control, whereas total CQAs content varied in a little range (0.71–1.21 mg g−1) without methyl jasmonate (MeJA) elicitation (CK)
The selected cell samples were exposed to MeJA for 0, 8, 20, and 40 h, and both total CQAs content and its fold changes were highest in G40h (19.59 mg g−1, 17.65 times), followed by G20h (6.81 mg g−1, 6.49 times), G8h (1.05 mg g−1, 1.57 times), and G0h (0.711 mg g−1, 1 time)
Summary
Gardenia jasminoides Ellis (G. jasminoides) is an evergreen shrub of family Rubiaceae, which is widely distributed in Southern China. Seven CQAs compounds in G. jasminoides cultured cell were identified via ultraperformance liquid chromatography/quadrupole timeof-flight mass spectrometry (UPLC-TOF-MS/MS), namely, 3-caffeoylquinic acid (3-CQA), 4-caffeoylquinic acid (4CQA), 5-caffeoylquinic acid (5-CQA), 3,5-dicaffeoylquinic acid (3,5-diCQA), 4,5-dicaffeoylquinic acid (4,5-diCQA), 3,5-dicaffeoyl-4-O-(3-hydroxyl-3-methyl)-glutaroylquinic acid [3,5-diC(HMG)QA], and malonyl-4,5-O-dicaffeoylquinic acid (M-4,5-diCQA) (Liu et al, 2018). In these CQAs, 3,5diC(HMG)QA and M-4,5-diCQA are the characteristic metabolites for G. jasminoides and have not been identified in other plants with high CQAs content, such as Coffea arabica and Lonicera japonica
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