Browsing by Author "Gaddam, Subhash Reddy"

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    COP1 mediates light-dependent regulation of flavonol biosynthesis through HY5 in Arabidopsis
    (Elsevier B.V., 2021) Bhatia, Chitra; Gaddam, Subhash Reddy; Pandey, Ashutosh; Trivedi, Prabodh Kumar
    Flavonols, a class of flavonoids, accumulate as protective agents in response to various stresses. Among various environmental stimuli, light is one of the factors regulating flavonol production. MYB12/11/111, members of the R2R3 MYBs family, regulates spatio-temporal flavonol accumulation in Arabidopsis. Although various studies indicate at the involvement of an E3 ubiquitin ligase CONSTITUTIVE PHOTOMORPHOGENIC 1 (COP1) and ELONGATED HYPOCOTYL 5 (HY5) in flavonoid biosynthesis in response to UV-B, the regulatory roles of these components under visible light are yet to be investigated. Here, we demonstrate that flavonol accumulation in Arabidopsis is light-regulated. Furthermore, our analysis suggests that MYB12 is a HY5-dependent light-inducible gene and plays a key role in the activation of the flavonol biosynthesis in response to light. Our results indicate the involvement of COP1 in the dark-dependent repression of MYB12 expression and flavonol accumulation. In addition, results also suggest that the effect of COP1 on MYB12 is indirect and is mediated through HY5, a direct transcriptional activator of the MYB12. Together these findings indicate that COP1 acts as a master negative regulator of flavonol biosynthesis in the dark.
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    Low temperature enhanced flavonol synthesis requires light-associated regulatory components in Arabidopsis thaliana
    (Oxford University Press, 2018) Bhatia, Chitra; Pandey, Ashutosh; Gaddam, Subhash Reddy; Hoecker, Ute; Trivedi, Prabodh Kumar
    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.