Abstract
Prohydrojasmon (PDJ) is a synthetic jasmonate derivative that is primarily used as a growth regulator, but its mechanism of action is unclear. In this study, we elucidated the effects of PDJ on phytochemical production in red leaf lettuce. The PDJ treatments promoted the accumulation of phenolic compounds in aerial plant parts. An LC-MS analysis revealed that these accumulated compounds were identified as cyanidin-3-O-glucoside, cyanidin-3-O-(6″-O-malonyl)-glucoside and cyanidin-3-O-(6″-O-malonyl)-glucoside methyl ester. The abundance of these compounds in lettuce extracts increased significantly in response to the PDJ treatment. Additionally, the LC-MS analysis also identified the accumulated phenolic compounds in the extracts of PDJ-treated lettuce, including caffeoyltartaric acid, chlorogenic acid, caffeoylmalic acid, chicoric acid, and dicaffeoylquinic acid. Gene expression analyses indicated the PDJ treatments upregulated the expression of PAL, F3H, and ANS genes in lettuce. These results suggest that PDJ treatments enhance the expression of genes involved in the synthesis of anthocyanins and phenolic compounds, resulting in an increase in the quantities of these compounds, which reportedly have various functions affecting human physiology.
Highlights
The demand for foods rich in phytochemicals has recently increased [1]
We investigated the compounds and molecular mechanisms in lettuce affected by PDJ using liquid chromatography–mass spectrometry (LC-MS)-based methods to identify the unknown compounds
The metabolites absorbed at 540 nm containing the anthocyanin, were, respectively, 2.7-and 4.2-times higher in the lettuce plants treated with 100 and 200 μM than in the control plants (Figure 1A)
Summary
The demand for foods rich in phytochemicals has recently increased [1]. There is considerable epidemiological evidence that polyphenols promote health and decrease the risk of various diseases, including cancers and cardiovascular diseases [2,3]. Enhancing flavonoid biosynthesis pathways by modulating environmental conditions may be useful for promoting phytochemical production in crops. Jasmonic acid and its derivatives are plant hormones and/or plant growth regulators in higher plants that control fruit ripening and coloration (including pigment accumulation). They can induce the biosynthesis of secondary compounds, including phenylpropanoid derivatives, caffeic acids, flavonols, and anthocyanins [17,18]. Lettuce and komatsuna grown under artificial light were treated with several PDJ concentrations, which enhanced the production of some phenolics, polyphenols, and anthocyanins in lettuce leaves [27]. We conducted gene expression analyses to clarify the regulation of enzymes involved in the phenylpropanoid derivative synthesis pathway in PDJ-treated lettuce
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