Abstract
A rice proteinase, REP-1 degrades seed storage proteins, and expression of the gene, Rep1 is induced by gibberellin (GA). The promoter region contains GA response element (GARE) to which GAMyb bind and a cis-element including CAACTC core sequence designated CARE, and these elements are required for GA response of Rep1. CARE interacts with a transcription factors containing a Myb motif in the C-terminal region, its gene designated CTMyb1. The differences of the transcription start sites of CTMyb1 result in two polypeptides, designated CTMyb1L (521 amino acid residues) and CTMyb1S (409 amino acid residues). The transient expression of CTMyb1L had no effect on activity of Rep1 promoter, but CTMyb1S activated Rep1 promoter with OsGAMyb synergistically. CTMyb1S interacted with rice prolamin box binding factor (RPBF) known to interact with OsGAMyb. In addition, RPBF activated Rep1 promoter. These results suggest that Rep1 expression is involved in complex consisting of CTMyb1S, RPBF and OsGAMyb.
