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Item Arabidopsis CAM7 and HY5 physically interact and directly bind to the HY5 promoter to regulate its expression and thereby promote photomorphogenesis(American Society of Plant Biologists, 2014) Abbas, Nazia; Maurya, Jay P.; Senapati, Dhirodatta; Gangappa, Sreeramaiah N.; Chattopadhyay, SudipArabidopsis thaliana CALMODULIN7 (CAM7), a unique member of the calmodulin gene family, plays a crucial role as a transcriptional regulator in seedling development. The elongated HYPOCOTYL5 (HY5) bZIP protein, an integrator of multiple signaling pathways, also plays an important role in photomorphogenic growth and light-regulated gene expression. CAM7 acts synergistically with HY5 to promote photomorphogenesis at various wavelengths of light. Although the genetic relationships between CAM7 and HY5 in light-mediated seedling development have been demonstrated, the molecular connectivity between CAM7 and HY5 is unknown. Furthermore, whereas HY5-mediated gene regulation has been fairly well investigated, the transcriptional regulation of HY5 is largely unknown. Here, we report that HY5 expression is regulated by HY5 and CAM7 at various wavelengths of light and also at various stages of development. In vitro and in vivo DNA-protein interaction studies suggest that HY5 and CAM7 bind to closely located T/G- and E-box cis-acting elements present in the HY5 promoter, respectively. Furthermore, CAM7 and HY5 physically interact and regulate the expression of HY5 in a concerted manner. Taken together, these results demonstrate that CAM7 and HY5 directly interact with the HY5 promoter to mediate the transcriptional activity of HY5 during Arabidopsis seedling development.Item CAM7 and HY5 genetically interact to regulate root growth and abscisic acid responses(Taylor & Francis Group, 2014) Abbas, Nazia; Chattopadhyay, SudipCAM7, 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.Item Molecular interactions of GBF1 with HY5 and HYH during light-mediated seedling development in Arabidopsis thaliana(American Society for Biochemistry and Molecular Biology, 2012) Singh, Aparna; Ram, Hathi; Abbas, Nazia; Chattopadhyay, SudipArabidopsis bZIP transcription factor, GBF1, acts as a differential regulator of cryptochrome-mediated blue light signaling. Whereas the bZIP proteins, HY5 (elongated hypocotyl 5) and HYH (HY5 homologue), are degraded by COP1-mediated proteasomal pathways, GBF1 is degraded by a proteasomal pathway independent of COP1. In this study, we have investigated the functional interrelations of GBF1 with HY5 and HYH in Arabidopsis seedling development. The genetic studies using double and triple mutants reveal that GBF1 largely acts antagonistically with HY5 and HYH in Arabidopsis seedling development. Further, GBF1 and HY5 play more important roles than HYH in blue light-mediated photomorphogenic growth. This study reveals that GBF1 is able to form a G-box-binding heterodimer with HY5 but not with HYH. The in vitro and in vivo studies demonstrate that GBF1 co-localizes with HY5 or HYH in the nucleus and physically interacts with both of the proteins. The protein-protein interaction studies further reveal that the bZIP domain of GBF1 is essential and sufficient for the interaction with HY5 or HYH. Taken together, these data demonstrate the functional interrelations of GBF1 with HY5 and HYH in Arabidopsis seedling development.Item HY1 genetically interacts with GBF1 and regulates the activity of the Z-box containing promoters in light signaling pathways in Arabidopsis thaliana(Elsevier, 2012) Prasad, V. Babu Rajendra; Gupta, Nisha; Nandi, Ashis; Chattopadhyay, SudipArabidopsis HY1/HO1, heme oxygenase enzyme, catalyses the oxygenation of heme to produce biliverdin, an essential step in the phytochrome-chromophore biosynthesis pathway. GBF1/ZBF2 is a G/Z-box binding bZIP protein that plays a dual but opposite regulatory roles in blue light-mediated seedling development and gene expression. Here, we show the genetic interactions of HY1 and GBF1 in seedling photomorphogenesis, and the role of HY1 in the regulation of promoters containing the Z-box light responsive element. Our results indicate that whereas the additional mutation in GBF1 does not affect the phenotype of hy1 mutant seedlings in red or far-red light, the additional mutation in HY1 suppresses the hyper photomorphogenic phenotype of gbf1 in BL. Further, transgenic studies using promoter-reporter constructs indicate that functional HY1 is essential for the optimal induction of Z-box containing synthetic and native promoters at various stages of Arabidopsis growth and development. Thus, this study establishes a functional relation of HY1 with GBF1, and HY1-mediated regulation of Z-box containing promoters in Arabidopsis seedling development.Item MYC2, a bHLH transcription factor, modulates the adult phenotype of SPA1(Landes Bioscience, 2010) Gangappa, Sreeramaiah N.; Chattopadhyay, SudipMYC2 and SPA1 are two key regulatory proteins that negatively regulate light-controlled Arabidopsis seedling development. We have recently demonstrated the genetic and molecular relationships of MYC2 and SPA1 in light and JA (jasmonic acid) signaling pathways. Here, we have further shown the genetic interactions between these two proteins in flowering time and lateral root development.