The sprout inhibitors chlorpropham and 1,4-dimethylnaphthalene elicit different transcriptional profiles and do not suppress growth through a prolongation of the dormant state

Chlorpropham (CIPC) and 1,4-dimethylnapthalene (DMN) are used to control postharvest sprouting of potato tubers. CIPC alters microtubule structure and function resulting in inhibition of cell division. The mechanism of action of DMN is unknown but, because it is a natural product found in potato tubers, there is speculation that it inhibits sprout growth by prolonging the dormant state. To address this issue, the effects of CIPC and DMN on abscisic acid (ABA) content and gene expression in potato tuber meristems were determined and compared to those found in dormant and non-dormant meristems. Dormancy progression was accompanied by a dramatic decline in ABA content and the ABA levels in meristems isolated from CIPC- and DMN- treated tubers were identical to the levels found in nondormant meristems demonstrating that sprout repression is not a function of elevated ABA. Evaluation of transcriptional profiles using cDNA microarrays demonstrated that there were similarities between CIPC- and DMN- treated tuber tissues particularly in transcripts that encode phosphatases and proteins associated with oxygen-related metabolism. Despite these similarities, there were significant differences in transcript profiles derived from treatment with either CIPC or DMN and the dormant state. These results suggested the mechanisms-of -action of DMN and CIPC are distinct and not due to a prolongation of the normal dormant condition.