Transcriptional activator of alpha-amylase expression that binds to 5'-CAACTGTC-3' motif in target gene promoter (PubMed:11743113). Positive regulator of abscisic acid (ABA) responses leading to growth arrest during seed germination (PubMed:17217461). 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 MYB65 and MYB101, promotes the programmed cell death (PCD) the vacuolation of protein storage vacuoles (PSVs) in the aleurone layers during seed germination (PubMed:20699403). Binds to a GARE site (GA-response element) in the LEAFY promoter, essential for its gibberellic acid (GA)-mediated induction (PubMed:15226253). Together with MYB65, facilitates anther and tapetum development (PubMed:15722475). Mostly expressed in stems, shoot apices, flowers and floral shoot tips, and, to a lower extent, in roots (e.g. root tips), seedlings, 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. Weak expression in the vegetative shoot apex. High levels in primordial leaves. Strongly expressed in the inflorescence apex, and, to some extent, in the inflorescence stem, the vascular tissue, and the vascular tissue in leaf primordia. In the gynoecium, confined to ovules. In developing anthers detected in developing locules of immature anthers and later, at low levels, in pollen grains (PubMed:11743113). In flowers, expressed in sepals, style, receptacle, anther filaments, especially in young anthers, and connective but not in anthers themselves (PubMed:15722475). Accumulates at the shoot apex upon the transition from short- to long-day photoperiods leading to flowering and after gibberellins (GAs) treatment (PubMed:11743113). Repressed by microRNA159 (miR159a and miR159b) in vegetative tissues (PubMed:15226253, PubMed:20699403, PubMed:17916625). Specific expression in floral organs and in the shoot apices is regulated via miR159-mediated degradation (PubMed:15722475). Repressed in germinating seeds by miR159-mediated cleavage in an abscisic acid (ABA) and ABI3-dependent manner, probably to desensitize hormone signaling during seedling stress responses (PubMed:17217461, PubMed:18305205). Slightly induced by ethylene and cytokinins (PubMed:9839469). 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). 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).