Sesquiterpene lactone dehydroleucodine selectively induces transient arrest in G2 in Allium cepa root meristematic cells

Dehydroleucodine is a sesquiterpene lactone recently isolated from aerial parts of a medicinal herb, Artemisia douglasiana Besser. We have previously shown that 25 and 100 microM dehydroleucodine slowed down onion root growth by 30 and 70%, respectively, affecting neither cell viability nor cell elongation. In the present study we analyze the effect of dehydroleucodine on cell cycle phases in onion (Allium cepa L.) root meristematic cells synchronized with caffeine or caffeine and hydroxyurea. Synchronized root cells treated with 100 and 200 microM dehydroleucodine present an interphase lengthening of 5.2 h and 8.2 h, respectively. The S-phase length, estimated by 3H]thymidine incorporation assay, was 6 h for both control roots and roots that had been immersed in dehydroleucodine. The peak of 3H]leucine incorporation was observed 6 h after release from synchronization in controls and in dehydroleucodine-treated roots, indicating that protein synthesis in G2 was not affected. Thus, these results show that dose-dependently dehydroleucodine selectively induces a transient arrest of meristematic cell in G2 and that dehydroleucodine can be used experimentally as a cell cycle suppressor.