Tradescantia Sister-Chromatid-Exchange (SCE) Bioassay for Environmental Mutagens

Tradescantia paludosa (spiderwort) has been one of the classical materials for cytogenetic studies since the late 1930s, and it possesses a number of endpoints to measure genotoxicity. Cytogenetic and genetic endpoints include chromosome/chromatid aberrations in its mitotic cells of microspores, root meristems, pollen tubes; meiotic pollen mother cells and gene mutation in the cells of staminal hairs. Although sister chromatid exchange (SCE) was first discovered in the plant root meristem of Allium cepa, the SCE technique has not yet been developed for Tradescantia root tip cells. Based upon the principles and technical procedures to measure SCEs in other plant systems, a standard SCE protocol was developed for Tradescantia in this study. Unlike the other plant system, Tradescantia roots developed from stem cuttings were used for SCE analysis. The major steps of this protocol include: root initiation, 5-bromodeoxyuridine (5-BrdU) treatment, thymidine chasing, colchicine treatment, fixation, pectinase digestion, squashing the meristematic cells under the coverglass, removal of coverglass, treatment with Hoechst and sodium salt solutions, UV-light treatment, staining with Giemsa. Well prepared slides were photographed under 400X magnification and analyzed for SCE frequencies. In addition, the spontaneous SCE frequency of Tradescantia was compared with those of Vicia and Allium.