5-Bromodeoxyuridine: A specific inhibitor of cytokinin-habituation in tobacco cell culture.

Cytokinin-habituated cells of Nicotiana tabacum L. cv. "Havana 425" are able to grow in culture without added cytokinin. The thymidine analogue, 5-bromodeoxyuridine (BUdR), which selectively inhibits differentiation of animal cells, blocks expression of the cytokinin-habituated phenotype in culture. This effect is prevented by thymidine and is reversible. These findings suggest that habituation and animal cell differentiation have a common mechanism. BUdR provides a useful tool for investigating the metabolism of cell division factors and its regulation in higher plant cells.