Proliferation-dependent pattern of expression of a dihydrofolate reductase-thymidylate synthase gene from Daucus carota

The pattern of expression of a carrot dhfr-ts gene was evaluated
in different plant organs, in somatic embryos, and in
hypocotyl explants induced to dedifferentiate in vitro by the
addition of the synthetic auxin 2,4 dichorophenoxyacetic
acid. The promoter of this gene was also placed upstream of
a uidA (GUS) reporter gene and, using biolistic and protoplasts
transient expression assays, was shown to drive a particularly
high level of expression in actively growing suspension
cells. The results from these expression analyses combined
with the presence of putative cell cycle-related cis-acting
elements in the dhfr-ts promoter, strongly point to a cell
division-dependent expression of this gene.