Luo, H., Dept. of Botany and Plant Pathology, Purdue University, West Lafayette, IN 47907, United States, AgriBioTech, Inc., 530 Liberty Lane, West Kingston, RI 02892, United States
Lyznik, L.A., Dept. of Botany and Plant Pathology, Purdue University, West Lafayette, IN 47907, United States, Pioneer Hi-Bred International, Inc., 7300 NW 62nd Avenue, Johnston, IA 50131, United States
Gidoni, D., Department of Plant Genetics, Inst. of Field and Garden Crops, Volcani Center, PO Box 6, Bet Dagan 50250, Israel
Hodges, T.K.

We have studied the feasibility in Arabidopsis of using a site-specific recombination system FLP/FRT, from the 2 μm plasmid of yeast, for making plant hybrids. Initially, Arabidopsis plants expressing the FLP site-specific recombinase were crossed with plants transformed with a vector containing kanamycin-resistance gene (npt) flanked by FRT sites, which also served to separate the CaMV35S promoter from a promoterless gusA. Hybrid progeny were tested for excision of the npt gene and the positioning of 35S promoter proximal to gusA. GUS activity was observed in the progeny of all crosses, but not in the progeny derived from the self-pollinated homozygous parents. We then induced male sterility in Arabidopsis plants using the antisense expression of a pollen- and tapetum-specific gene, bcp1, flanked by FRT sites. Upon cross-pollination of flowers on the same male-sterile plants with pollen from FLP-containing plants, viable seeds were produced and the progeny hybrid plants developed normally. Molecular analyses revealed that the antisense expression cassette of bcp1 had been excised in these plants. These results show for the first time that a site-specific recombinase can be used to restore fertility in male-sterile plants, providing an alternative method for the production of hybrid seeds and plants.