TRANSFORMATION OF KALANCHOE-BLOSSFELDIANA MEDIATED BY AGROBACTERIUM-TUMEFACIENS AND TRANSGENE SILENCING

A method for Agrobacterium-mediated transformation of Kalanchoe blossf eldiana Poelln. (Crassulaceae) and quantitative analysis of the expres sion pattern of beta-glucuronidase (GUS) gene are reported. Leaf segme nts were infected with the Agrobacterium strain LBA4404 having a binar y vector plasmid pBI121 or its derivatives and cultured on Murashige a nd Skoog medium supplemented with 0.5 mg/l benzyladenine, 2 mg/l indol eacetic acid, 300 mg/l carbenicillin and 20 mg/l kanamycin (selection medium) for regeneration. Primary transformants (R(0)) with three kind s of chimeric GUS genes were obtained in different experiments, and So uthern blot analysis confirmed the presence of the GUS gene in their g enome. The integrated GUS gene(s) seemed to be silenced in about half of the transformants. There was no clear correlation between copy numb er and expression level of the GUS gene. Observed levels of GUS activi ty within transformants were divided into three classes: (1) high acti vity, (2) low activity and (3) near-zero activity. Selfed progeny (R(1 )) of a near-zero activity and a low activity transformant segregated to high, low and near-zero activity. Southern blot analysis unexpected ly revealed no clear difference in the band pattern of the GUS gene; s ome progeny showed high activity while some progeny showed near-zero a ctivity derived from the near-zero-activity transformant. Copyright (C ) 1996 Elsevier Science Ireland Ltd