Transcription factor that binds to the E-box-containing promoter regions of the transcription factors TDR and EAT1, activating their expression. May have a role in specifying the cell pattern of the inner anther walls and functioning in meiosis progression. Required for male reproduction (PubMed:24755456). Acts downstream of UDT1 and GAMYB, but upstream of TDR1 and EAT1 in pollen development (PubMed:24894043). Homodimer (By similarity). Interacts with TDR, but not with EAT1 (PubMed:24755456, PubMed:24894043). Highly expressed in anthers; strong expression in the middle layer and tapetum, and weak expression in the endothecium. In anthers, expressed from the meiosis stage to mitosis, with maximum levels at stages 7 and 8, when meiosis initiates, and when endothecium and the middle layer become condensed, respectively. Has normal vegetative growth, inflorescence and flower morphology, however has smaller anthers and does not produce mature pollen grains during reproductive stage. After stage 6, during which anther forms four somatic layers, the three inner anther wall layers remain undifferentiated. Meiosis progresses normally from leptotene stage to metaphase I, but is arrasted at anaphase I and no cytokinesis occurs at prophase II, resulting in degenerated meiocytes. Belongs to the bHLH protein family.