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Articles by P.V. Joshua
Total Records ( 2 ) for P.V. Joshua
  D.R.S. Suneetha , A. Arundhati , G.S. Rao and P.V. Joshua
  The present study tends to investigate the role of DNA methylation in silencing and expression of rolA, B and C genes in Nicotiana glauca and its hybrid, respectively. Exposure of the hybrid seed to 5-azacytidine, a DNA hypomethylating agent resulted severe alterations in morphology, early tumor induction and loss of phytohormone independent growth. On the contrary, DNA hypermethylation caused by cefotaxime treatment resulted in enhanced rate of tumorigenesis and callus growth. The above results convey that changes in DNA methylation in the hybrid plants possess a significant effect on tumorigenesis. Therefore, DNA isolated from the parents, hybrid and tumor were restriction digested with cytosine methylation specific isoschizomers MspI and HpaII; and Southern analysis was carried out using rolA, B and C genes as probes. The size of the bands differed in MspI and HpaII digests of N. glauca, hybrid and tumor whereas no signals were observed in Nicotiana langsdorffii. Results were discussed in terms of silencing of rolA, B and C genes in N. glauca and their expression in the hybrid. Hence, it could be concluded that DNA hypermethylation of rol genes in N. glauca resulted in their silencing causing normal morphology and behavior of the plant, whereas DNA hypomethylation of rol genes was responsible for their expression in the hybrid causing morphological abnormalities and tumorigensis.
  P.V. Joshua , D.R. Salomi Suneetha , A. Arundhati and G. Seshagiri Rao
  Present study tends to investigate the existence of the bacterial oncogenes- rol genes of Agrobacterium rhizogenes Riker., in Nicotiana rustica, N. plumbaginifolia and their hybrid. These Nicotiana species and hybrid were normal morphologically under field conditions without any neoplastic growth. So, the habituation studies were carried out to identify the presence of rol genes by culturing the leaf discs on hormone supplemented Murashige and Skoog medium and then shifting to MS basal medium. Habituation showed phytohormone independent growth response even after shifting to MS basal medium indicating the presence of rol genes. Then, Polymerase Chain Reaction analysis showed amplification of rol A, B and C genes in N. rustica, rol A and C in N. plumbaginifolia and the hybrid. The amplified genes were sequenced and deposited in GenBank. The homology between the novel genes was compared with the rol genes of A. rhizogenes as well as the other plants species containing rol gene homologues using Pairwise sequence alignment search tool. Results were discussed in terms of the occurrence of bacterial genes in plants, the extent of their expression and the probable reasons for silencing of the foreign genes.
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