Low temperature enhanced flavonol synthesis requires light-associated regulatory components in Arabidopsis thaliana

Abstract

Plants are continuously exposed to myriad of stresses, which lead to the formation of secondary metabolites including flavonoids. Studies suggest that low temperature exposure leads to enhanced flavonoid accumulation in Arabidopsis thaliana. In addition, flavonoid biosynthesis is regulated by light through various regulatory factors. Therefore, plant may possess the capability to integrate light and low temperature signals for survival under freezing conditions. However, detailed molecular mechanism and the regulatory factors associated with light- and low temperature- responsive flavonoid biosynthesis remain largely unknown. Here, we report a strict requirement of light for the low temperature- enhanced flavonol biosynthesis. Low temperature-induced expression of biosynthetic genes as well as flavonol accumulation was hampered in ELONGATED HYPOCOTYL (hy5) and myb11myb111myb12 triple mutants as compared to wild-type (WT) in Arabidopsis. Over-expression of AtHY5 in the hy5 mutant restored induction of gene expression and flavonol accumulation in response to low-temperature in light. Metabolite and gene expression analysis also suggests negative role of CONSTITUTIVE PHOTOMORPHOGENIC1 (COP1) in accumulation of flavonols in response to low temperature. Over-expression of AtMYB12 enhanced accumulation of flavonols under low-temperature in a light-dependent manner. Together, our analysis suggests requirement of HY5 and flavonol-specific MYB regulatory factors for low temperature-induced flavonol synthesis.