Isolation and characterization of colchicine-resistant cell lines of carrot

Colchicine changes plant cell shape by disrupting cortical microtubules. This change in cell shape involves the loss of cell rigidity and, subsequently, an increase in cell volume. Dimethylsulfoxide prevents the colchicine-stimulated cell enlargement but cannot maintain the cell shape. We have isolated colchicine-resistant cell lines, col-4 and col-3, which can maintain their cell shape in colchicine at 10⁻⁴ and 10⁻³ M , respectively. Both col-4 and col-3 accumulate a low level of tubulins when grown in colchicine while the wild-type cells do not. Hence the ability to accumulate tubulins correlates with the ability to maintain cell shape. The mechanism of colchicine-resistance of col-4 is not clear but may be associated with the expression of 5 proteins with molecular masses of 64, 45, 29, 28, and 26 kDa. Col-3 cells were isolated from col-4 and presumably shared this mechanism of resistance since they also express these 5 proteins. However, col-3 cells have an additional defect resulting in reduced colchicine uptake.