T-DNA TAGGING AND CHARACTERIZATION OF A NOVEL MERISTEM-SPECIFIC PROMOTER FROM TOBACCO

We have evaluated T-DNA mediated plant promoter tagging, with a left-b order-linked promoterless firefly luciferase (luc) construct, as a str ategy for the isolation of novel plant promoters. In a population of a pproximately 300 transformed tobacco plants, IO lines showed LUC activ ity, including novel tissue-specific and developmental patterns of exp ression. One line, showing LUC activity only in the shoot and root api cal meristems, was further characterised. Inverse PCR was used to ampl ify a 1.5 kb fragment of plant DNA flanking the single-copy T-DNA inse rtion in this line. With the exception of a 249 bp highly repetitive e lement, this sequence is present as a single copy in the tobacco genom e, and is not homologous to any previously characterised DNA sequences . Sequence analysis revealed the presence of several motifs that may b e involved in transcriptional regulation. Transgenic tobacco plants tr ansformed with a transcriptional fusion of this putative promoter sequ ence to the beta-glucuronidase (uidA) reporter gene, showed GUS activi ty confined to the shoot tip and mature pollen. This promoter may be u seful to direct the expression of genes controlling the transition to flowering, or genes to reduce losses due to pests and stresses damagin g plant apical meristems.