Transgenic haploid plants ofNicotiana rustica produced by bombardment-mediated transformation of pollen

Immature pollen fromNicotiana rustica was bombarded with gold particles coated with plasmid DNA encoding neomycin phosphotransferase II (NPTII) and -glucuronidase (GUS) genes which, respectively, are under the control of the cauliflower mosaic virus (CaMV) 35S promoter and nopaline synthase (NOS) terminator in the plasmid. Kanamycin-resistant pollen embryoids were selected from the bombarded pollen cells and two independent lines of transgenic plants were regenerated. Enzyme assays showed that one has both NPTII and GUS activities and the other only weak NPTII activity. Southern blot analyses indicated that the former has a DNA fragment corresponding to the intact expression cassettes for both genes in its genome; whereas the latter lacks intact expression cassettes for both genes and has only the intactnptII coding sequence in its genome. The transgenic plants of both lines have 24 chromosomes, confirming haploidy, and they are infertile. These results indicate that transgenic haploid plants can be produced directly by the bombardment-mediated transformation of immature pollen.