Establishment of the Self-incompatibility (S) Locus-directed Transposon Tagging System in Antirrhinum

In order to perform mutational studies on genes from the self-incompatibility (S) locus, an S locus-directed transposon tagging system was established in Antirrhinum. Cultivated lines of Antirrhinum majus contain many molecularly well-characterized transposons, but are self compatible due to the presence of a nonfunctional S locus (Sc). In this study, an active transposon (Tam5) from the Cycloidea (Cyc) locus controlling flower asymmetry in A. majus was introduced to a position tightly linked to the functional S locus from self incompatible interspecific hybrids (A. majus×hispanicum) through genetic recombination. RFLP (restriction fragment length polymorphism) analysis showed that the transposon is 3 cM (centiMorgan) away from the S locus and retains high transpositional activity with a germinal excision frequency of 20%. Possible implications of the linkage between the S locus and genes controlling floral phenotypes were discussed. An active transposon tightly linked to the S locus constructed here will facilitate the generation of insertional mutants of the S locus encoded genes and may lead to dissecting their precise roles during self-incompatible reactions.