Abstract
A MTX-resistant line of Daucus carota has been selected and characterized. With respect to the parental line the slow-growing resistant cells are smaller with a lower macromolecular content, and as judged by flow cytofluorometry of DAPI stained nuclei, with a profound modification of chromosomal arrangement. Dihydrofolate reductase (DHFR), the target enzyme, showed unaltered kinetic parameters but its activity was almost 10-fold higher on a DNA basis. Rate of MTX uptake was remarkably reduced. In addition to the aspects common to the MTX-resistant plants previously described, this line is characterized also by a 10-fold increase of folate concentrations in the cells. A mechanism of resistance based on the increase in the cell of the DHFR substrate is considered. The hypothesis that overproduction of DHFR and of folates are related to a coregulatory mechanism is also discussed.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
