Pollen selection: a transgenic reconstruction approach.

A transgenic reconstruction experiment has been performed to determine the feasibility of male gametophytic selection to enhance transmission of genes to the next sporophytic generation. For tobacco pollen from a transgenic plant containing a single hygromycin-resistance (hygromycin phosphotransferase, hpt-) gene under control of the dc3 promoter, which is active in both sporophytic and gametophytic tissues, 3 days of in vitro maturation in hygromycin-containing medium was sufficient to result in a 50% reduction of germinating pollen, as expected for meiotic segregation of a single locus insert. Pollination of wild-type plants with the selected pollen yielded 100% transgenic offspring, as determined by the activity of the linked kanamycin-resistance gene--present within the same transferred T-DNA borders--under control of the nos promoter. This is direct proof that selection acting on male gametophytes can be a means to alter the frequency of genes in the progeny.