Nucleotide sequence analysis of TL-DNA of Agrobacterium rhizogenes agropine type plasmid. Identification of open reading frames.

Abstract

We have determined the nucleotide sequence of the Ri TL-DNA region from an Agrobacterium rhizogenes agropine-type plasmid using subcloned regions from the essentially identical Ri TL-DNAs from strains A4 and HRI. This sequenced region of 21,126 base pairs (bp) contains the complete TL-DNA region of the Ri plasmid as determined by analysis of TL-DNA borders in the genome of infected, clonal, Convolvulus arvensis plants. The left and right borders of the TL-DNA are flanked by 25-bp sequences which match the 25-bp terminal sequences found near the borders of T-DNA regions of Agrobacterium tumefaciens Ti plasmids. Other DNA sequences similar to these 25-bp terminal sequences are found within the TL region, and some of these sequences appear to be associated with Ri TL-DNA structures found in transformed tobacco plants. The TL-DNA region contains 18 open reading frames, many of which have 5' and 3' regulatory elements similar to those found in eukaryotic genes. In many cases, CCAAT and TATA elements were found upstream from putative transcriptional initiation codons, and poly(A) addition (AATAAA) elements were observed in presumed 3'-noncoding regions. Comparison of Ri TL-DNA coding and noncoding sequence regions with T-DNA sequence regions from octopine type Ti plasmid pTi15955 reveals no extensive sequence homologies.