The Viviparous-1 gene and abscisic acid activate the C1 regulatory gene for anthocyanin biosynthesis during seed maturation in maize.

The Viviparous-1 (Vp1) gene is required for expression of the C1 regulatory gene of the anthocyanin pathway in the developing maize seed. We show that VP1 overexpression and the hormone, abscisic acid (ABA), activate a reporter gene driven by the C1 promoter in maize protoplasts. Cis-acting sequences essential for these responses were localized. Mutation of a conserved sequence in the C1 promoter abolishes both ABA regulation and VP1 trans-activation. An adjacent 5-bp deletion blocks ABA regulation but not VP1 trans-activation. The latter mutant reconstructs the promoter of c1-p, an allele that is expressed during seed germination but not during seed maturation. We suggest that VP1 activates C1 specifically during maturation by interacting with one or more ABA-regulated transcription factors.