Transcription activator (PubMed:24278028, PubMed:25268707). Binds to 5'-CAACTGTC-3' and/or 5'-TAACAAA-3' motif in target gene promoter (e.g. alpha-amylase) to promote their expression (PubMed:11743113). Positive regulator of abscisic acid (ABA) responses leading to growth arrest during seed germination (PubMed:17217461). Promotes the expression of aleurone-related genes (e.g. CP1, CP, GASA1, BXL1 and BXL2) in seeds. Together with MYB33 and MYB65, promotes the programmed cell death (PCD) leading to vacuolation of protein storage vacuoles (PSVs) in the aleurone layers during seed germination (PubMed:20699403). Maybe involved in the regulation of leaves lamina morphogenesis (PubMed:25268707). Involved in pollen grain development (PubMed:22101548). Together with MYB97 and MYB120, functions as a male factor that controls pollen tube-synergid interaction in fertilization. Required for pollen tube growth arrest and sperm cell release in the female gametophyte, probably via the regulation of pollen tube-specific gene expression (PubMed:24278028, PubMed:23791732). Detected in the vegetative nucleus of mature pollen grains and pollen tubes. Present mostly in flowers, siliques and floral shoot tips (PubMed:11743113, PubMed:25268707). Expression is restricted to the subapical pith cells of both vegetative and flowering plants and to the hypocotyl hook (PubMed:11743113). Expressed in pollen grains and pollen tube (PubMed:23791732, PubMed:24278028). Mostly expressed in mature pollen grains, and, to a lower extent, in inflorescences and siliques (PubMed:24278028). Present in a small patch of cells on the innermost side of the hypocotyl hook of the germinating seedling, in the subapical pith cells of plants growing vegetatively, in a similar zone of expanding cells both in developing inflorescence stems, and below mature flowers and elongating siliques (PubMed:11743113). Accumulates in the pollen tube nucleus during pollen tube growth through the pistil (PubMed:23791732). Repressed in germinating seeds by microRNA159 (miR159)-mediated cleavage in an abscisic acid (ABA) and ABI3-dependent manner, probably to desensitize hormone signaling during seedling stress responses (PubMed:15226253, PubMed:17217461). Induced by increased upon gibberellic acid (GA) treatment (PubMed:20699403). Hyposensitivity to abscisic acid (ABA) (PubMed:17217461). Reduced expression levels of aleurone-related genes (e.g. CP1, CP, GASA1, BXL1 and BXL2) in seeds. The triple mutant myb33 myb65 myb101 has a male sterility and exhibits slower protein storage vacuoles (PSVs) vacuolation rate in aleurone layers upon seed germination (PubMed:20699403). Reduced production of abnormal pollen grains with misarranged male germ unit (MGU) (PubMed:22101548). The triple mutant myb97 myb101 myb120 is impaired in pollen tube growth arrest and subsequent sperm cell release in the female gametophyte thus leading to a drastically reduced fertility. Altered pollen tube-specific gene expression (PubMed:23791732, PubMed:24278028).