Plant expression signals of theAgrobacteriumT-cyt gene

Abstract

Within the 5' and 3' non-coding regions of the T-cyt gene from the octopine T-DNA of Agrobacterium tumefaciens sequences required for expression of this gene in plant cells were identified by deletion mutagenesis. The results show that 184 bp of the 5' non-coding region and 270 bp of the 3' non-coding region are sufficient for wild-type expression. Within the 5' non-coding region two essential expression signals were identified: (1.) an activator element located between -185 and -129 with respect to the ATG start codon and (2.) one out of two TATA boxes. Deletions of the activator element or the two TATA boxes resulted in nonfunctional genes. Deletion of the upstream TATA box and both putative CAAT boxes did not significantly affect expression. Within the 3' non-coding region, the polyadenylation box most distal to the stop codon was not essential for expression, but sequences more upstream, including a second polyadenylation box were found to be required for wild-type expression.

An enhancer-like element present in the promoter of a T-DNA gene from the Ti plasmid of Agrobacterium tumefaciens

“…The 780 activator seems to differ from the ags TATA-distal domain by not having a strong functional requirement for additional upstream elements. In this respect, the 780 activator is similar to the activator element present in the T-cyt gene (cytokinin production, gene 4 of T-left) promoter that also requires only a TATA for wild-type activity (28). The T-cyt activator, however, does not appear to be a typical enhancer-like element since it does not function when the distance between it and TATA is increased over that of the wild-type gene (28).…”

Site-directed mutagenesis of the enhancer region of the 780 gene promoter of T-DNA

“…The c repeat, which is present in the promoter regions of 7 of the 13 T-DNA genes (octopine type T-DNA), comprises a portion of a major controlling element required for expression of the T-cyt promoter [ 14], and is located 5 bp downstream of the CBF binding site within this element [27]. In the present study mutation of a c repeat boosted activity in two cases (mutations 89 and 92); however, placing mutations at both of these sites simultaneously had a negative effect.…”

“…Although the T-DNA genes are of bacterial origin, they are expressed in a eukaryotic background and hence the structure of their promoters resembles that of indigenous plant genes. For this reason, T-DNA has been utilized as a source of plant promoters readily amenable to analysis [3,6,10,14] and as a vector to facilitate the expression of foreign genes in plants.…”

A single amino acid substitution beyond the C2H2-zinc finger in Ros derepresses virulence and T-DNA genes in Agrobacterium tumefaciens

“…The negatively-regulated virulence genes are contained in the virC and virD operons, whose products process the T-DNA at its left and right borders for transfer from the bacterial cell to the plant host cell (reviewed recently in [2,3]). For nopaline-type Ti plasmids such as pTiC58, the T-DNA is a speci¢c 25-kb sector of the Ti plasmid and contains the plant oncogenes ipt, iaaM and iaaH, whose promoters are regulated by the plant transcription system recognizing their TATA boxes [4,5] to synthesize isopentenyl transferase, tryptophan monooxygenase and indoleacetamide amidohydrolase, respectively.…”