Transcription activator (PubMed:24278028). Binds to 5'-CAACTGTC-3' and/or 5'-TAACAAA-3' motif in target gene promoter to promote their expression (By similarity). Together with MYB97 and MYB101, 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 pollen tubes. 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). Accumulates in the pollen tube nucleus during pollen tube growth through the pistil. Accumulates in pollen tube 4 hours after pollen germination. Disrupted pollen tube growth (PubMed:19714218). 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).