Institutional Publications

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    Regulation of TOP2 by various abiotic stresses including cold and salinity in pea and transgenic tobacco plants
    (Oxford University Press, 2005) Hettiarachchi, Gardhi H. C. M.; Reddy, Malireddy K.; Sopory, Sudhir K.; Chattopadhyay, Sudip
    Although abiotic stress affects plant growth and development, demonstration of its direct effect on regulation of the components of the DNA replication machinery is largely unknown. In this work, we demonstrate that the expression of TOP2 (encoding topoisomerase II) is up-regulated by various abiotic stresses including salinity and low temperature, and phytohormones such as ABA (abscisic acid) and SA (salicylic acid). Transgenic studies with different deletion versions of the TOP2 promoter in tobacco define several promoter determinants responsible for specific abiotic stress responsiveness. Taken together, these results demonstrate a direct involvement of stress in the transcriptional regulation of TOP2.
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    Light mediated regulation defines a minimal promoter region of TOP2
    (Oxford University Press, 2003) Hettiarachchi, G. H. C. M.; Yadav, Vandana; Reddy, M. K.; Chattopadhyay, Sudip; Sopory, Sudhir K.
    Light signaling has been demonstrated to be an important factor for plant growth and development; however, its role in the regulation of DNA replication and cell cycle has just started to be unraveled. In this work, we have demonstrated that the TOP2 promoter of Pisum sativum (pea) is activated by a broad spectrum of light including far-red light (FR), red light (RL) and blue light (BL). Deletion analyses of the TOP2 promoter in transformed plants, Arabidopsis thaliana and Nicotiana tobaccum (tobacco), de®ne a minimal promoter region that is induced by RL, FR and BL, and is essential and suficient for light-mediated activation. The minimal promoter of TOP2 follows the phytochromemediated low- ̄uence response similar to complex light regulated promoters. DNA±protein interaction studies reveal the presence of a DNA binding activity speci®c to a 106 bp region of the minimal promoter that is crucial for light-mediated activation. These results altogether indicate a direct involvement of light signaling in the regulation of expression of TOP2, one of the components of the DNA replication/cell cycle machinery.