Transcription activator, when associated with MYB75/PAP1, MYB90/PAP2 or TT2. Involved in epidermal cell fate specification. Regulates negatively stomata formation but promotes trichome formation. Together with MYB66/WER, promotes the formation of non-hair cells in root epidermis cells in the N position. Whereas together with CPC, promotes the formation of hair cells in root epidermis cells in the H position by inhibiting non-hair cell formation. Seems also to play a role in the activation of anthocyanin biosynthesis, probably together with MYB75/PAP1. Involved in seed mucilage production. Activates the transcription of GL2. Efficient DNA binding requires dimerization with another bHLH protein (By similarity). Homodimer and heterodimer with GL3. Interacts with CPC, MYB0/GL1, MYB5, MYB23, MYB113, MYB114, MYB75/PAP1, MYB90/PAP2, TT2, TRY, TTG1 and MYB66/WER. Moves from developing hair cells (trichoblasts) to developing non-hair cells (atrichoblasts). Ubiquitous with higher levels in buds and flowers. Specifically localized in developing root hair cells. Expressed in epidermal root hair cells (trichoblasts) and moves to root hairless cells (atrichoblasts) by a cell-to-cell movement through plasmodesmata (at protein level). Localized in trichome developing region of leaves, prior to trichome initiation. Levels increase in initiating and young trichome cells, but dropped in the pavement cells between trichomes. Disappears in mature trichomes. By UV treatment. Negatively regulated by MYB66/WER, GL3 and BHLH2 in the developing non-hair cells, and positively regulated by CPC and TRY in the developing hair cells.