Embryonal recombination and germline inheritance of recombined FRT loci mediated by constitutively expressed FLP in tobacco

FLP site-specific recombination has been shown in transgenic plants to exci se DNA sequences between target FRT sites, and thereby activate transgenes in plants. In previous reports, crossing of tobacco plants expressing FLP r ecombinase from a CaMV-35s promoter with plants containing the target FRT s ites, hybrid plants with deletion sectors were generated, which were infreq uently transmitted to progeny. In this report we evaluate the occurrence of recombination in F-1 hybrid seed derived from crosses of different FLP and FRT-reporter target lines and the germinal transmission of recombined loci from these hybrids to F-2 progeny. Twenty hybrids were generated from cros ses of independent five FLP-active lines and four FRT-reporter target lines . In one hybrid, FLP deletions occurred at an early stage, prior to seed ma turation, and the deletions from this hybrid were more efficiently transmit ted to F-2 progeny. The demonstration of FLP-mediated recombination activit y and germinal inheritance of the recombined FRT loci are supported by both molecular and enzymatic evidence.