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Different expression patterns of the promoters of the NgrolB and NgrolC genes during the development of tobacco genetic tumors

Nagata, N., Kosono, S., Sekine, M., Shinmyo, A., Syono, K.
Plant & cell physiology 1996 v.37 no.4 pp. 489-498
hybrids, Nicotiana glauca, neoplasms, roots, transgenic plants, developmental stages, stems, genetic disorders, Nicotiana langsdorffii, gene expression, genes, cell differentiation, enzyme activity, histochemistry, beta-glucuronidase, leaves
Hybrids (F1) between Nicotiana glauca and N. langsdorffii are prone to develop tumorous tissues on normal-type F1 tissues, namely, genetic tumors. To investigate the patterns of expression of Ngrol genes during the development of genetic tumors, we performed an analysis of transgenic genetic tumors that harbored the promoters of the NgrolB and NgrolC genes fused to a reporter gene for beta-glucuronidase (GUS) using a tumorization-redifferentiation system derived from F1 plants in vitro. Histochemical analysis of the expression of NgrolB-GUS in normal-type F1 transgenic plants revealed GUS activity in meristematic zones, while in NgrolC-GUS transformed plants the activity was detected mainly in the vascular systems of various organs. Tumorous tissues, which arose spontaneously as a consequence of aging or were induced by cutting, showed high levels of GUS expression under the control of promoters of both the NgrolB and the NgrolC gene. Time course analysis during tumorization that followed cutting of leaves of normal-type F1 plants showed clearly that NgrolB-GUS was expressed in all dividing cells in the cut region after 3 days. By contrast, the expression of NgrolC-GUS was detected in organized tissues, such as procambium in teratomatous tumors, 7-10 days after cutting treatment. During redifferentiation from genetic tumors to normal-type plants, the expression of GUS under control of both Ngrol promoters decreased and expression resembled that in normal-type tissues. These results suggest the possibility that the Ngrol genes might be involved in formation of genetic tumors and, moreover, that the expression of NgrolB might be linked to mitosis and while that of NgrolC might be related to differentiation of tissues, such as the vascular system, in F1 plants.