Abstract
Expression of carrot ECP (DcECP) genes encoding late-embryogenesis abundant proteins is embryo-specific and ABA-inducible. The expression is regulated by C-ABI3, a carrot homologue of Arabidopsis ABI3. To understand the molecular mechanisms controlling ABA-inducible and embryo-specific gene expression, we compared and analyzed the promoter regions of some ECP genes. The accumulation of DcECPs mRNA in response to ABA was not inhibited by an inhibitor of protein synthesis, cycloheximide. These results indicate that the ABA-inducible expression of the DcECPs did not require de novo protein synthesis. Sequence comparison among some ECP gene promoters revealed that the promoters contained several conserved motifs including ABRE (ABA responsive element)-like ACGT core motifs, and an Sph box (CATGCATG), which has been identified as a motif mediating gene activation of maize antocyanin regulatory gene C1. To investigate the promoter activity of DcECP31 promoter region, we carried out a deletion analysis with a transient assay system using protoplasts of embryogenic cells or with a transformation system using embryogenic cells of carrot. We found that the -250bp upstream region of the DcECP31 promoter is sufficient for embryo-specific and ABA-inducible promoter activity. Following deletion analysis of DcECP40 promoter, we clarified that the distal (-670∼-390) and proximal regions (-140∼-50), are essential for the ABA-inducible expression.
