ISSN:
1617-4623
Keywords:
Agrobacterium tumefaciens
;
T-DNA borders
;
Intergeneric gene transfer
;
pseudoborder
;
Insertional activation
;
Aberrant T-DNAs
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Summary During Agrobacterium tumefaciens infection, the T-DNA flanked by 24 by imperfect direct repeats is transferred and stably integrated into the plant chromosome at random positions. Here we measured the frequency with which a promoterless reporter gene is activated after insertion into the Nicotiana tabacum SR1 genome. When adjacent to the right or left T-DNA border sequences, at least 35% of the transformants express the marker gene, suggesting preferential T-DNA insertion (〉70%) in transcriptionally active regions of the plant genome. When the promoterless neomycin phosphotransferase II (nptII) gene is located internally in the T-DNA, the activation frequency drops to 1% since gene activation requires T-DNA truncation. These truncation events in the nptII upstream region occur independently of the nature of the upstream sequence and of the T-DNA length. Deletion of the right border region prevents the detection of activated marker genes. Therefore, T-DNA truncation probably occurs after synthesis of a normal T-DNA intermediate during the transfer and/or integration process. In the absence of border regions, expression of the nptII selectable marker directed by the nopaline synthase promoter was detected in 1 out of 105 regenerated calli, suggesting the possibility that any DNA sequence from the Ti plasmid can be transformed into the plant genome, albeit at a low frequency.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00271558
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