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.