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 excise DNA sequences between target FRT sites, and thereby activate transgenes in plants. In previous reports, crossing of tobacco plants expressing FLP recombinase from a CaMV-35s promoter with plants containing the target FRT sites, hybrid plants with deletion sectors were generated, which were infrequently 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 crosses 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 maturation, and the deletions from this hybrid were more efficiently transmitted to F-2 progeny. The demonstration of FLP-mediated recombination activity and germinal inheritance of the recombined FRT loci are supported by both molecular and enzymatic evidence.