|Srivastava, Vibha - UCB/ARS PLNT GENE EXP CTR|
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: January 16, 2002
Publication Date: January 16, 2002
Citation: Ow, D.W., Srivastava, V. 2002. Cre-mediated deletion product may be retained as a circular dna in transgenic plants. Meeting Abstract. Technical Abstract: Earlier we reported using the Cre recombinase to resolve complex multi-copy integration patterns into a single copy. This resolution process also removed the marker gene bar. Four complex-locus wheat lines were obtained by transformation with a lox-plasmid, pVS11. Each of the four lines was crossed to a cre line, Cre37. With one pVS11 derived line, VS10.1, we analyzed several F2 plants derived from VS10.1 X Cre37 crosses. In some of the F2 plants, we detected the circular loxP-bar-nos3' fragment (deleted from pVS11 locus), referred to as the bar-circle, in leaf DNA samples (Srivastava et.al., 1999). This was an uncommon and unexpected event. Presence and transmission of bar-circle was tightly linked with both cre and the pVS11 locus in F2 and F3 plants. To investigate why this deletion product is retained whereas in most other cases it is lost, we segregated the cre and lox loci in the bar circle plants into cre* and VS10.1* lines, respectively. We found that cre* generated detectable level of bar-circle when crossed with another pVS11 line, VS10.2. However, VS10.1* did not generate bar-circle when crossed with Cre37. Since a nucleotide change was not detected in the coding sequence of cre*, we suspect that cre* has undergone an epigenetic modification, which resulted in insufficient cre expression in embryonic tissue. Sufficient cre expression, probably occurs only late in development. As a result, Cre-mediated excision of bar-circle occurs in non-dividing cells and therefore not diluted through subsequent divisions. Molecular and genetic data on bar-circle plants will be presented.