Wound-inducible and organ-specific expression of ORF13 from Agrobacterium rhizogenes 8196 T-DNA in transgenic tobacco plants.

Tissue-specific expression of the ORF13 promoter from Agrobacterium rhizogenes 8196 was assessed throughout the development of transgenic tobacco plants using a GUS reporter gene. ORF13 exhibited high activity in roots but with different patterns of expression. The activity of the ORF13 promoter in vascular tissues increased from the base to the tip of the stem. The ORF13 promoter is wound inducible in a limited area adjacent to the wound site. The time course of wound induction of ORF13 in transgenic tobacco containing an ORF13 promoter-GUS translational fusion was similar to that previously described for genes involved in plant defense responses. A series of 5' deletions of the ORF13 promoter fused to the beta-glucuronidase gene was examined for expression in roots and leaves of transgenic plants. Cis-acting elements that modulate quantitative expression of the transgene after wounding were detected.

rol genes of Agrobacterium rhizogenes cucumopine strain: sequence, effects and pattern of expression.

By sequencing the central region of the cucumopine-type T-DNA of Agrobacterium rhizogenes strain 2659, we identified three open reading frames homologous, to different extents, to ORFs 10, 11 and 12 (rolA, B and C) of the agropine-type (1855) T-DNA. Recombinant Agrobacterium strains encompassing the ORFs of 2659 T-DNA--which we refer to as rol alpha, beta and gamma--were utilized to infect carrot discs and to obtain transgenic tobacco plants, in order to compare the morphogenetic capabilities to those of the 1855 rol genes. Moreover, a long segment of the 5' non-coding region of rol alpha and rol beta was fused to the GUS reporter gene and the pattern of expression and the responsiveness to auxin of the constructs was analysed in transgenic tobacco. Differences in the auxin requirement for root induction between the 2659 rol genes and their respective 1855 counterparts were pinpointed. These differences are not due to gene regulation and presumably reflect functional differences in the proteins encoded. Differences were also observed in the pattern of expression of rol beta in roots of transgenic plants, as compared to rolB. In addition, the pattern of expression of rol alpha-GUS construct in roots was found to be analogous to that observed for a construct driven by two of the five regulatory domains of the rolB promoter.

A new open reading frame, encoding a putative regulatory protein, in Agrobacterium rhizogenes T-DNA.

We report the presence of an open reading frame, named ORF13a, encoding a putative regulatory protein on the T-DNA of Agrobacterium rhizogenes 8196 Ri plasmid. Homologous ORFs are present at the same location in two other types of Ri plasmids. We present evidence that ORF13a is transcriptionally active. Expression of ORF13a was investigated by analysis of glucuronidase (GUS) activity in transgenic tobacco containing an ORF13aGUS fusion. The gene fusion was expressed at higher level in roots than in leaves. The putative protein encoded by ORF13a has an isoelectric point of 11.55 and carries SPXX repeated motifs suggesting a possible regulatory function for this gene.