Dose-, time-, and tissue-dependent effects of 5-bromo-2′ -deoxyuridine on the in-vitro organogenesis of Arabidopsis thaliana

Abstract

Vigorous organogenesis can be induced from hypocotyl and root explants of Arabidopsis thaliana using a two-step culture procedure consisting of preculture on callus-inducing medium (CIM) and subsequent culture on shoot-inducing medium (SIM) or root-inducing medium (RIM). With this culture system, we examined the influence of 5-bromo-2′-deoxyuridine (BrdU), a thymidine (dT) analogue, on plant organogenesis in vitro. Treatment with BrdU during SIM or RIM culture had negative effects on shoot and root redifferentiation over a broad range of concentrations. When explants were exposed to low concentrations of BrdU during preculture and then transferred onto BrdU-free SIM, shoot redifferentiation was accelerated significantly. At higher doses, BrdU treatment during the pre-culture inhibited shoot redifferentiation strongly in hypocotyl explants, but not in root explants. This suggests that a target of the BrdU action lies within the process of acquisition of cell proliferation competence specifically involved in hypocotyl dedifferentiation. These effects of BrdU were counteracted by the simultaneous addition of excess dT. BrdU-pretreated and untreated explants did not differ significantly in the phytohormone dependency of shoot redifferentiation. Our results provide a basis for future studies on plant organogenesis combining pharmacological analysis with BrdU as a probe and molecular genetics with Arabidopsis mutants.