Characterization of Transgenic Kalanchoe and Petunia with Organ-Specific Expression of GUS or GA2ox Genes Led by the Deletion BOX-I Version (dBI) of the PAL1 Promoter

In the present work, transgenic Kalanchoe blossfeldiana and Petunia hybrida with overexpression of Nicotiana GA(2)ox inserted in pCAMBIA1303 T-DNA are investigated. To avoid possible adverse effects of constitutive overexpression a modified Pisum PAL1 promoter was used, in which the BOX-I AC-rich motif had been deleted (dBI-deletion BOX-I). To investigate the tissue-specificity of the dBI and PAL1 promoters, their sequences were fused with the GUS gene, cloned into two types of vectors (pCAMBIA1303 and p6N) and introduced by Agrobacterium-mediated transformation into both species. GUS-transgenic lines were tested for the GUS mRNA in stems, leaves, and roots with the use of RT-PCR and GUS-stained tissues were visualized and compared with the use of light microscopy. The dBI promoter leads to expression of GUS mRNA and GUS activity in stems and petioles but not in roots or leaves, whereas the PAL1 promoter is less specific. All transgenic lines were tested for transgene copy number using Southern blot analysis. Transgenic Kalanchoe plants with Nicotiana GA2ox exhibited more than twofold reduction in stem length but no reduction of the number of internodes. Similarly, in Petunia transgenic plants, the stem length was reduced threefold. The leaves of the transgenic Kalanchoe plants were smaller, as convex as those of the youngest leaves of the non-transgenic control plants, and had reduced petiole length. The leaves from transgenic Petunia plants were similar in shape to those of the non-transgenic control plants but significantly smaller.