Transcriptional activator of alpha-amylase expression that binds to 5'-CAACTGTC-3' motif in target gene promoter (PubMed:11743113). In vegetative tissues, inhibits growth by reducing cell proliferation. Promotes the expression of aleurone-related genes (e.g. CP1, CP, GASA1, BXL1 and BXL2) in seeds. Together with MYB33 and MYB101, promotes the programmed cell death (PCD) the vacuolation of protein storage vacuoles (PSVs) in the aleurone layers during seed germination (PubMed:20699403). Together with MYB33, facilitates anther and tapetum development (PubMed:15722475). Mostly expressed in roots (e.g. root tips), stems, pollen, shoot apices, flowers and floral shoot tips, and, to a lower extent, in leaves and siliques. In germinating seeds, present in the root tip and in a linear array of up to 20 to 30 cells above the root tip. Strongly expressed in the inflorescence apex, and, to some extent, in the inflorescence stem, the vascular tissue, and the vascular tissue in leaf primordia (PubMed:11743113). In flowers, expressed in sepals, style, receptacle, anther filaments, and connective but not in anthers themselves (PubMed:15722475). Repressed by microRNA159 (miR159a and miR159b) in vegetative tissues (PubMed:20699403, PubMed:17916625, PubMed:15226253). Specific expression in floral organs and in the shoot apices is regulated via miR159-mediated degradation (PubMed:15722475). Slightly induced by ethylene and salicylic acid (PubMed:16463103). 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). The myb33 myb65 double mutant is defective in anther development, with a tapetum undergoing hypertrophy at the pollen mother cell stage, resulting in premeiotic abortion of pollen development and male sterility. This sterility is conditional, fertility being increased both under higher light or lower temperature conditions (PubMed:15722475).