Transcription factor required for female gametophyte fertility. Acts redundantly with MYB64 to initiate the FG5 transition during female gametophyte development. The FG5 transition represents the switch between free nuclear divisions and cellularization-differentiation in female gametophyte, and occurs during developmental stage FG5. Expressed in ovary septum and stamen filament. During female gametogenesis, expressed in the female gametophyte at stage FG4 (four-nucleate stage) in all four nuclei. Expressed in the central cell in unfused polar nuclei at stage FG5 and secondary nucleus at stage FG6. Not expressed in mature female gametophytes (stage FG7). No visible phenotype under normal growth conditions, but in the double mutant plants myb64 and myb119 the female gametophytes fail to cellularize, resulting in enlarged coenocytes with supernumerary nuclei. Extended C-terminus.