The Regulatory Functions of the rolB and rolC Genes of Agrobacterium rhizogenes are Conserved in the Homologous Genes (Ngrol) of Nicotiana glauca in Tobacco Genetic Tumors

To compare patterns of expression between the Ngrol genes ofN. glauca and the Rirol genes of Agrobacterium rhizogenes, weperformed fluorometric and histochemical analysis of transgenicgenetic tumors on the hybrid of Nicotiana glauca x N. langsdorffü(Fl) that harbored a rß- glucuronidase (GUS) reportergene fused to the promoter of NgrolB, NgrolC, RirolB or RirolC The promoters of NgrolB and NgrolCNgrolC had 2- to 3-fold loweractivity than those of RirolB and RirolC However, the changesin patterns of GUS activity caused by deletion of NgrolB andNgrolCpromoters were similar to those of RirolB and RirolC promoters.This result suggests that the cis-acting sequences that regulatethe level of expression of RirolB and RirolC are conserved inthe NgrolB and NgrolC promoters. Furthermore, an auxin dependent(NAA-dependent) increase in GUS activity was observed in thecase of NgrolB-GUS and RirolB-GUS. Histochemical analysis showedGUS activity encoded by both NgrolB-GUS and RirolB-GUS in normal-typeFl transgenic plants was located in meristematic zones, whilethat encoded by NgrolC-GUS and RirolC-GUS was detected mainlyin vascular systems of various organs. Thus, the patterns ofexpression of the Ngrol genes were the same as those of theRirol genes in terms of promotion by auxin and tissue-specificity,indicating that regulatory mechanisms for both sets of geneshave been conserved during the evolution of the genus Nicotianaafter transfer from a progenitor of Agrobacterium to that ofNicotiana. (Received May 2, 1995; Accepted June 13, 1995)