Transcription factor that plays a crucial role in tapetum development. Required for male fertility and pollen differentiation within the developing anther. Plays a major role in maintaining tapetum development, starting in early meiosis. Required for pollen mother cell meiosis. May regulate the anther-specific cysteine protease CP1 and lipid-transfer proteins C4 and C6 (PubMed:16141453). Required for anther development. Functions in parallel with GAMYB to regulate early anther development. Functions upstream of the transcription factor TDR and may positively regulate its transcription (PubMed:20590996). During anther development, expressed at the late premeiosis and meiosis stages in both the anther wall and the microspores. After meiosis, expressed in the tapetum, connective tissue, and vascular bundles. Male sterility due to failure of tapetum to differentiate and pollen to mature. Belongs to the bHLH protein family. Contains a degenerate basic motif not likely to bind DNA.