title: Cell cycle stage-specific differential expression of topoisomerase I in tobacco BY-2 cells and its ectopic overexpression and knockdown unravels its crucial role in plant morphogenesis and development.
abstract: DNA topoisomerases catalyze the inter-conversion of different topological forms of DNA. Cell cycle coupled differential accumulation of topoisomerase I (Topo I) revealed biphasic expression maximum at S-phase and M/G1-phase of cultured synchronized tobacco BY-2 cells. This suggested its active role in resolving topological constrains during DNA replication (S-phase) and chromosome decondensation (M/G1 phase). Immuno-localization revealed high concentrations of Topo I in nucleolus. Propidium iodide staining and Br-UTP incorporation patterns revealed direct correlation between immunofluorescence intensity and rRNA transcription activity within nucleolus. Immuno-stained chromosomes during metaphase and anaphase suggested possible role of Topo I in resolving topological constrains during mitotic chromosome condensation. Inhibitor studies showed that in comparison to Topo I, Topo II was essential in resolving topological constrains during chromosome condensation. Probably, Topo II substituted Topo I functioning to certain extent during chromosome condensation, but not vice-versa. Transgenic Topo I tobacco lines revealed morphological abnormalities and highlighted its crucial role in plant morphogenesis and development.
authors.affiliation: Plant Molecular Biology Group, International Centre for Genetic Engineering and Biotechnology, Aruna Asaf Ali Marg, New Delhi 110067, Delhi, India.
authors.forename: Badri Nath
authors.initials: BN
authors.lastname: Singh
authors.affiliation: Plant Molecular Biology Group, International Centre for Genetic Engineering and Biotechnology, Aruna Asaf Ali Marg, New Delhi 110067, Delhi, India.
authors.forename: Yashwanti
authors.initials: Y
authors.lastname: Mudgil
authors.affiliation: Department of Botany, University of Kashmir, Hazratbal, Srinagar 190006, Jammu and Kashmir, India.
authors.forename: Riffat
authors.initials: R
authors.lastname: John
authors.affiliation: Plant Molecular Biology Group, International Centre for Genetic Engineering and Biotechnology, Aruna Asaf Ali Marg, New Delhi 110067, Delhi, India.
authors.forename: V Mohan Murali
authors.initials: VM
authors.lastname: Achary
authors.affiliation: Plant Molecular Biology Group, International Centre for Genetic Engineering and Biotechnology, Aruna Asaf Ali Marg, New Delhi 110067, Delhi, India.
authors.forename: Manas Kumar
authors.initials: MK
authors.lastname: Tripathy
authors.affiliation: Plant Molecular Biology Group, International Centre for Genetic Engineering and Biotechnology, Aruna Asaf Ali Marg, New Delhi 110067, Delhi, India.
authors.forename: Sudhir K
authors.initials: SK
authors.lastname: Sopory
authors.affiliation: Plant Molecular Biology Group, International Centre for Genetic Engineering and Biotechnology, Aruna Asaf Ali Marg, New Delhi 110067, Delhi, India.
authors.forename: Malireddy K
authors.initials: MK
authors.lastname: Reddy
authors.affiliation: Plant Molecular Biology Group, International Centre for Genetic Engineering and Biotechnology, Aruna Asaf Ali Marg, New Delhi 110067, Delhi, India. Electronic address: tanushri@icgeb.res.in.
authors.forename: Tanushri
authors.initials: T
authors.lastname: Kaul
mesh_terms: D002453:Cell Cycle; D002478:Cells, Cultured; D004264:DNA Topoisomerases, Type I / Q000235:genetics* / Q000378:metabolism; D000066630:Ectopic Gene Expression; D005455:Fluorescent Antibody Technique; D018506:Gene Expression Regulation, Plant; D055785:Gene Knockdown Techniques; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D014026:Nicotiana / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism
chemical_list: D010940:Plant Proteins; D004264:DNA Topoisomerases, Type I
keywords: Chromosome condensation; Nicotiana tabaccum; Plant development; Synchronized BY-2 cell; Topoisomerase