Institutional Publications

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Subject: search.filters.subject.HY5

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Now showing 1 - 7 of 7
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    HY5 and ABI5 transcription factors physically interact to fine tune light and ABA signaling in Arabidopsis
    (Springer Nature Publishing AG, 2021) Bhagat, Prakash Kumar; Verma, Deepanjali; Sharma, Deepika; Sinha, Alok Krishna
    Plants undergo numerous transitions during their life-cycle and have developed a very complex network of signaling to integrate information from their surroundings to effectively survive in the ever-changing environment. Light signaling is one of the crucial factors that govern the plant growth and development from the very first step of that is from seedling germination to the flowering. Similarly, Abscisic acid (ABA) signaling transduces the signals from external unfavorable condition to the internal developmental pathways and is crucial for regulation of seed maturation, dormancy germination and early seedling development. These two fundamental factors coordinately regulate plant wellbeing, but the underlying molecular mechanisms that drive this regulation are poorly understood. Here, we identified that two bZIP transcription factors, ELONGATED HYPOCOTYLE 5 (HY5), a positive regulator of light signaling and ABA-INSENSITIVE 5 (ABI5), a positive regulator of ABA signaling interacts and integrates the two pathways together. Our phenotypic data suggest that ABI5 may act as a negative regulator during photomorphogenesis in contrast, HY5 acts as a positive regulator of ABA signaling in an ABA dependent manner. We further showed that over-expression of HY5 leads to ABA-hypersensitive phenotype and late flowering phenotype. Taken together, our data provides key insights regarding the mechanism of interaction between ABI5-HY5 that fine tunes the stress and developmental response in Arabidopsis.
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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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    CAM7 and HY5 genetically interact to regulate root growth and abscisic acid responses
    (Taylor & Francis Group, 2014) Abbas, Nazia; Chattopadhyay, Sudip
    CAM7, a member of CaM family in Arabidopsis, acts as a transcriptional regulator and enhances photomorphogenic growth and light regulated gene expression under various light conditions. HY5, a bZIP transcription factor, promotes photomorphogenesis at multiple wavelengths of light including far red, red, and blue light. Very recently, it has been shown that CAM7 and HY5 directly interact with the HY5 promoter to regulate the transcriptional activity of HY5 during Arabidopsis seedling development. In this study, we have investigated the root phenotype of cam7 hy5 double mutants and shown that CAM7 and HY5 genetically interact to control the root growth. We have further shown an interdependent function of HY5 and CAM7 in abscisic acid (ABA) responsiveness.
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    Molecular interaction of bZIP domains of GBF1, HY5 and HYH in Arabidopsis seedling development
    (Taylor & Francis, 2013) Ram, Hathi; Chattopadhyay, Sudip
    The bZIP proteins, GBF1, HY5 and HYH, play important regulatory roles in Arabidopsis seedling development. Whereas GBF1 plays a dual regulatory role, HY5 and HYH act as positive regulators of photomorphogenesis. The molecular and functional relations of GBF1 with HY5 and HYH in photomorphogenesis have recently been demonstrated. However, the possible interaction of bZIP domain of each of these proteins remains to be investigated. In this study, our results suggest that bZIP domains of HY5 and HYH are able to interact with the bZIP domain of GBF1. Taken together with the earlier study, (9) these results suggest that the N-terminal domain of GBF1 has an inhibitory effect on its interaction with HY5 and HYH.
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    Functional interconnections of HY1 with MYC2 and HY5 in Arabidopsis seedling development
    (BMC, 2012) Prasad, Babu Rajendra V; Kumar, Selva V; Nandi, Ashis; Chattopadhyay, Sudip
    Arabidopsis seedling development is controlled by many regulatory genes involved in multiple signaling pathways. The functional relationships of these genes working in multiple signaling cascades have started to be unraveled. Arabidopsis HY1/HO1 is a rate-limiting enzyme involved in biosynthesis of phytochrome chromophore. HY5 (a bZIP protein) promotes photomorphogenesis, however ZBF1/MYC2 (a bHLH protein) works as a negative regulator of photomorphogenic growth and light regulated gene expression. Further, MYC2 and HY1 have been shown to play important roles in jasmonic acid (JA) signaling pathways. Here, we show the genetic interactions of HY1 with two key transcription factor genes of light signaling, HY5 and MYC2, in Arabidopsis seedling development. Our studies reveal that although HY1 acts in an additive manner with HY5, it is epistatic to MYC2 in light-mediated seedling growth and gene expression. This study further demonstrates that HY1 additively or synergistically functions with HY5, however it works upstream to MYC2 in JA signaling pathways. Taken together, this study demonstrates the functional interrelations of HY1, MYC2 and HY5 in light and JA signaling pathways.
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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.