Evidence for the expression of the rol genes of Nicotiana glauca in genetic tumors of N. glauca X N. langsdorffii.

Thus far, no evidence has been presented that the rol genes (Ng rol) of Nicotiana glauca (Furner et al. 1986) are expressed in this plant. However, we found that the Ng rol genes were transcribed in genetic tumors formed in hybrids of N. glauca X N. langsdorffii. During the culture of such genetic tumors, the level of transcription of Ng rol B increased while that of Ng rol C decreased in parallel with an increase in the endogenous auxin level in the tissues. Moreover, the transcription of these genes was completely suppressed by the application of exogenous auxin. Since the measured endogenous level of auxin was rather low, the formation of tumors in these hybrids can be tentatively explained as a consequence of the expression of rol genes that is responsible for the increased sensitivity to auxin of the hybrids. This novel finding is discussed in relation to the cause of genetic tumors in Nicotiana.