Function of the genes specifically expressed in the genetic tumors

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Agrobacterium rhizogenes is responsible for the formation of adventitious roots known as hairy roots. The molecular basis of this disease is the transfer of the DNA segments (Rirol genes) of Ri plasmid into the plant genome. In the genome of untransformed Nicotiana glauca, Ngrol genes, homologous to Rirol genes, were detected. We have already reported NgrolB and NgrolC genes expressed in the genetic tumor tissues spontaneously developed on F1 plants between N. glauca (-group) and N. langsdorffii (+group).In this study, we found NgORF13 also expressed in the genetic tumors. Furthermore, the expression of NgrolB, NgrolC and NgORF13 was found to be regulated by the plant hormones, auxin, cytokinin and jasmonic acid, respectively. On the other hand, the transgenic N. tabacum (-group) revealed both NgORF13 and NgrolC promoted the Rirol-mediated hairy root induction. Overexpression of NgORF13 and NgrolC, under the control of 35S promoter, provoked morphological abnormalities in the transgenic N. tabacum. No tumors, however, developed on these plants.To clarify whether or not the Ngrol genes are the tumor factor in group of tobacco, chimeric genes, such as NgrolB〜ORF14, 35S-NgrolC, 35S-NgORF13, were separately introduced into N. langsdorffii. The tumor formation also couldn't be observed in these cases. The results indicate that Ngrol genes aren't a unique factor of tumor formation in -group. The varied responses to plant growth regulators of these transgenic plants suggests, however, Ngrol genes cooperated with other unknown factor in -group tobacco might function on genetic tumor formation