The cell cycle genes cycA1;1 and cdc2Os-3 are coordinately regulated by gibberellin in planta.

Internodal growth of deepwater rice (Oryza sativa L.) can achieve rates of up to 10 mm h(-1). In submergence-induced plants, gibberellic acid activates the cell division cycle first at the G1 --> S phase transition with a subsequent increase in mitotic activity. The proteins cycA1;1 and cdc2Os-3 are the regulatory and catalytic subunits, respectively, of cyclin-dependent protein kinases (CDKs) which are central to cell cycle regulation. Both genes are regulated by gibberellic acid in a coordinate manner with transcripts accumulating in the G2 phase prior to the B2-type mitotic cyclins described previously (M. Sauter et al. 1995, Plant J 7: 623-632), suggesting a distinct role in regulating G2/M phase progression. Since cdc2Os-3 belongs to a group of CDKs that have no counterparts in animals, it may function in a plant-specific gibberellin-regulated cell division process.