Abstract
In Arabidopsis thaliana, shoot redifferentiation can be induced from hypocotyl explants by a two-step culture method. In which tissues are precultured on callus-inducing medium and then transferred onto shoot-inducing medium. Hypocotyl explants dedifferentiate and acquire competence for cell proliferation and then competence for shoot redifferentiation during preculture, and form shoot during culture on shoot-inducing medium. In contrast, root explants retain competence for cell proliferation and skip the acquisition step of cell proliferation competence. Shoot redifferentiation from hypocotyl explants was promoted by treatment with low concentrations of 5-bromodeoxyuridine (BrdU) during preculture and inhibited by BrdU-treatment at high concentrations. Since such inhibitory effect of BrdU was not observed in root explants, BrdU is supposed to impede the acquisition of cell proliferation competence. Analysis of the BrdU effect in combination with the srd2 mutation, which causes temperature sensitivity in the acquisition of cell proliferation competence, suggested that BrdU suppresses the SRD2 function.
