The effect of water stress on phytochemical accumulation, bioactive compounds and expression of key genes involved in flavonoid biosynthesis in Chrysanthemum morifolium L.

The present study was designed to evaluate water-induced alterations in non-enzymatic antioxidants as evidenced by the qualitative and quantitative properties of polyphenols and the molecular mechanism of phenylpropanoid pathway by the expression patterns of key genes (pal, chi, and f3 h) in two Chrysanthemum morifoilum cultivars. In addition, certain physiological alternations due to water stress were evaluated. Considerable differences were observed in leaf DPPH antioxidant activity as well as phenolic, flavonoid, and anthocyanin contents between the control and water-stressed plants in both cultivars. Expression profiles of the genes related to polyphenolic metabolism showed environment and cultivar-dependent responses as well as gene x environment interactions. Combining the data with HPLC analysis led to identification of six phenolic compounds (namely, chlorogenicacid, rutin, ferulic acid, quercetin, apigenin, and luteolin) whose values generally increased with increasing water stress. Correlations were also established between certain compounds and the genes studied, which appears to be useful for further study of the flavonoid biosynthetic pathway. Moreover, a strong correlation was detected between inhibition percentage by DPPH assay and luteolin and chlorogenic acid, suggesting their contributions to the antioxidant capacity of the Chrysanthemum plant. Water stress stimulated the synthesis of luteolin, quercetin, and rutin in Taraneh cultivar as well as luteolin and apigenin in Azita cultivar through up regulating expression of chi gene. Finally, the current work deploys differential responses of cultivars to water stress toward further insight into how the pharmaceutical quality of Chrysanthemum in terms of its biochemical compounds may be enhanced.