Ronald C. Lundquist

Fertile transgenic corn plants

Transgenic friable, embryogenic oat callus cultures were selected for phosphinothricin (PPT) resistance following microprojectile bombardment with a plasmid encoding the Streptomyces hygroscopicus bar gene and the Escherichia coli uidA gene. From three microprojectile bombardment experiments, 111 PPT-resistant tissue cultures were shown to be transgenic based on Southern blot analysis. From one to more than 20 copies of the transgenes were integrated in the genome of the PPT-resistant tissue cultures. Coexpression of β-glucuronidase (GUS) activity due to expression of uidA was detected in 75% of the transgenic tissue cultures. Plants were regenerated from 38 of the 111 transgenic tissue cultures. Regenerated plants generally exhibited male sterility; however, more than 30 plants regenerated from one transgenic tissue culture were fully fertile. GUS activity in the seed of fertile regenerated plants and PPT resistance in progeny of these plants cosegregated with bar and uidA sequences demonstrating stable inheritance of the transgenes.

Transformation and inheritance of a hygromycin phosphotransferase gene in maize plants

Embryogenic maize (Zea mays L.) callus cultures were transformed by microprojectile bombardment with a chimeric hygromycin phosphotransferase (HPT) gene and three transformed lines were obtained by selecting for hygromycin resistance. All lines contained one or a few copies of the intact HPT coding sequence. Fertile, transgenic plants were regenerated and the transmission of the chimeric gene was demonstrated through two complete generations. One line inherited the gene in the manner expected for a single, dominant locus, whereas two did not.

Genetic complementation of Agrobacterium tumefaciens Ti plasmid mutants in the virulence region

SummaryMutants with Tn5 insertions in the vir region of the Agrobacterium tumefaciens TiC58 plasmid are unable to form crown-gall tumors. Complementation tests of these vir region mutants were carried out by constructing merodiploids in a recombination-deficient strain. Each merodiploid possessed a mutant TiC58 plasmid and a recombinant plasmid containing either the homologous wild-type DNA region or the homologous region containing a second Tn5 insertion. The analysis identified six complementation groups. Mutations in one of these complementation groups were not complemented in trans and represent a cis-dominant locus. The mutation in one complementation group showed variation in host range.