Abstract
Root epidermal cells differentiate into either root hair cells or hair-less cells in Arabidopsis. In current model, a transcriptional complex consisting of WER (R2R3-MYB transcription factor), GL3/EGL3 (bHLH transcription factor) and TTG1 (WD40 repeat protein) promotes GL2 (encoding an HD-Zip transcription factor) expression, which results in differentiation into hair-less cell. CPC (R3-MYB protein) inhibits formation of the WER-GL3/EGL3-TTG1 complex to repress GL2 expression, resulting in differentiation into root hair cell.
TTG2, encoding a WRKY transcription factor, regulates trichome development. TTG2 is expressed in atrichoblasts of roots as well as in trichomes. We found that TTG2 expression in roots was directly promoted by the WER-GL3/EGL3-TTG1 complex and was repressed by CPC. Transgenic Arabidopsis expressing chimeric TTG2 protein fused with transcription repression domain (TTG2:SRDX) formed root hairs from all epidermal cells of roots. In TTG2:SRDX lines, GL2 expression was repressed in roots, suggesting a possibility that TTG2 promotes GL2 expression.
