REGULATION OF AN EMBRYOGENIC CARROT GENE (DC-2.15) AND IDENTIFICATIONOF ITS ACTIVE PROMOTER SITES

According to previous studies the expression of the gene DC 2.15 is in duced in cultured carrot cells after a transfer to an auxin-free mediu m, where somatic embryo development occurs. This embryogenic gene enco des a proline-rich protein, which resembles proteins involved in auxin -controlled developmental processes. To understand the mechanism under lying the regulation of DC 2.15, an experimental approach has been emp loyed which allows the direct identification of the DC 2.15 promoter s tructure by applying PCR techniques. We demonstrate the presence of fi ve distinct promoter sequences highly similar in structure, but slight ly different in a common region of about 15 nucleotides, which contain the binding site for the GATA factor originally found in the human HO X gene. Activity of each promoter structure was assessed in developing somatic embryos containing the specific sequence fused to the beta-gl ucuronidase (GUS) reporter gene. For two of the five promoter structur es a drastic increase in activity was registered during the torpedo st age while the remaining three were inactive throughout the stages of s omatic embryogenesis.