Isolation and characterization of the PgDOF transcription factor in Platycodon grandiflorum

DNA binding with one finger (Dof) domain proteins are plant-specific transcription factors that are encoded by a multi-gene family in higher plants. A member of this gene family, PgDOF, was cloned from Platycodon grandiflorum. PgDOF was 489 bp in length and encoded 162 amino acids. The predicted protein contained 52 amino acids showing homology to the Dof domain and a putative nuclear localization signal near the carboxyl terminus. Alignment of sequences revealed that the DOF domain of PgDOF showed a 100% match to that of the Arabidopsis COG1 gene, which has been shown to negatively regulate phytochrome signaling. PgDOF was expressed highly in leaves and stems but at low levels in flowers and roots. In addition, PgDOF was shown to localize to the nucleus in transient expression assays in onion epidermal cells with the results confirmed in transgenic Arabidopsis.