Institutional Publications

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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.
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    GBF 1, a transcription factor of blue light signaling in Arabidopsis, is degraded in the dark by a proteasome-mediated pathway independent of COP 1 and SPA 1
    (The American Society for Biochemistry and Molecular Biology, Inc., 2008) Mallappa, Chandrashekara; Singh, Aparna; Ram, Hathi; Chattopadhyay, Sudip
    Arabidopsis GBF1/ZBF2 is a bZIP transcription factor that plays dual but opposite regulatory roles in cryptochrome-mediated blue light signaling. Here, we show the genetic and molecular interrelation of GBF1 with two well characterized negative regulators of light signaling, COP1 and SPA1, in photomorphogenic growth and light-regulated gene expression. Our results further reveal that GBF1 protein is less abundant in the dark- grown seedlings and is degraded by a proteasome-mediated pathway independent of COP1 and SPA1. Furthermore, COP1 physically interacts with GBF1 and is required for the optimum accumulation of GBF1 protein in light-grown seedlings. Taken together, this study provides a mechanistic view of concerted function of three important regulators in Arabidopsis seedling development.
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    SHW1, a common regulator of abscisic acid (ABA) and light signaling pathways
    (Landes Bioscience, 2008) Bhatia, Shikha; Gangappa, Sreeramaiah N.; Chattopadhyay, Sudip
    In our recent paper in Plant Physiology, we have reported the identification and functional characterization of a unique regulator, SHW1, a serine-arginine-aspartate rich protein in Arabidopsis seedling development.1 Genetic and molecular analyses have revealed that SHW1 functions in an independent and interdependent manner with COP1, and differentially regulates photomorphogenic growth and light regulated gene expression. Here, we show the involvement of photoreceptors in the function of SHW1. Our results have further revealed that SHW1 is a common regulator of light and ABA signaling pathways. These results along with some data described in Plant Physiology paper have been discussed here in a broader perspective.
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    Light regulated modulation of Z-box containing promoters by photoreceptor and downstream regulatory components, COP1 and HY5 in Arabidopsis thaliana
    (Wiley-Blackwell, 2002) Yadav, Vandana; Kundu, Snehangshu; Chattopadhyay, Debasis; Negi, Prem; Wei, Ning; Deng, Xing-Wang; Chattopadhyay, Sudip
    The Z-box is one of the light-responsive elements (LREs) found in the promoters of light inducible genes. We have studied the light responsive characteristics of Z-box containing synthetic as well as native promoters. We show that promoters with Z-box as a single LRE or paired with another LRE can respond to a broad spectrum of light. The response is primarily mediated by phyA, phyB and CRY1 photoreceptors at their respective wavelengths of light. We have demonstrated that CAB1 and Z-GATA containing promoters are down-regulated in hy5 mutants in the light. On the other hand, a promoter with Z-box alone is down-regulated in hy5 mutants both in dark and in light conditions, suggesting involvement of a similar regulatory system in the regulation of the promoter in two distinct developmental pathways: skotomorphogenesis and photomorphogenesis. Furthermore, similar to the CAB1 promoter, a Z-GATA containing promoter is derepressed in cop1 mutants in the dark. DNA±protein interaction studies reveal the presence of a DNA-binding activity that is speci®c to Z-box. These results provide insights into the regulation of the Z-box LRE mediated by various light signaling components.