Functional characterization of Arabidopsis Dof transcription factor AtDof4.1

The plant specific Dof (DNA Binding with One Zinc Finger) transcription factors (TFs) perform many different functions, and some members of this family appear to play an important role in the evolution of the vascular system characteristic of land plants. Here we report the functional characterization of a Dof TF from Arabidopsis (At4g00940-AtDof4.1). Transcriptional fusion with GUS or GFP reporter indicated that the AtDof4.1 strongly expresses in the young seedlings, particularly in the vascular tissues. The reporter expression was strictly restricted to the pericycle cells of the vascular tissues in the mature root zone and root cap while absent from the hypocotyls. The developmental phenotypes of its loss-of-function mutants were indistinguishable from those of the wild type probably due to the functional redundancy in the members of Arabidopsis Dof family. However, the overexpression lines showed severe growth retardation and delayed stem bolting and flowering. Similarly the overexpression of AtDof4.1 fusion with a super repressor domain (SRD) showed severely delayed flowering and defective reproductive organ development. In addition, AtDof4.1-SRD overexpression lines had the reduced size of the organs, such as leaves, flowers, and siliques. Due to similar morphology of overexpression AtDof4.1 and AtDof4.1-SRD lines, we suggest that AtDof4.1 functions as a transcriptional repressor.