Abstract
NtWIF was isolated as a down-stream transcription factor of WIPK from tobacco plants. To identify phosphorylation site(s) of NtWIF, we introduced mutations into the potential MAPK target site, Thr-Pro located in the N-terminus. When Thr-Pro site was replaced by Ala-Pro, Thr-Ala or Ala-Ala, transcriptional activities were completely lost even in the presence of WIPK.
Subsequently, we looked for target genes of NtWIF. Structually, the N-terminus of NtWIF shows a high similarity to the plant specific DNA binding domain of Auxin response factor (ARF). Gel shift assay using AuxRE motif containing TGTCTC sequence, that other ARFs recognize and bind to, showed that the full-length NtWIF was able to bind to AuxRE motif. Moreover, co-transfection of AuxRE-Luc reporter plasmid and NtWIF resulted in activation of reporter gene expression. These results suggested that target genes of NtWIF possess the AuxRE motif in their promoter regions.
