Submitted to: Plant Molecular Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/19/2010
Publication Date: 2/5/2010
Publication URL: http://hdl.handle.net/10113/45290
Citation: Campbell, M.A., Gleichnser, A., Alsbury, R., Horvath, D.P., Suttle, J.C. 2010. The Sprout Inhibitors Chlorpropham and 1,4-Dimethylnaphthalene Elicit Different Transcriptional Profiles and Do Not Suppress Growth Through a Prolongation of the Dormant State. Plant Molecular Biology. 73:181-189. Interpretive Summary: For an indeterminate period of time following harvest, potatoes will not sprout and are physiologically dormant. Dormancy is gradually lost during postharvest storage and the resultant sprouting is detrimental to the nutritional and processing qualities of potatoes destined for human consumption. For this reason, successful potato storage management requires the use of sprout-inhibiting chemicals to maintain process and nutritional qualities. To date, all commercial sprout inhibitors have been synthetic growth inhibitors with ever-stricter residue limits. Thus, there has been considerable effort devoted to identifying novel non-restricted sprout inhibitors. The natural product 1,4-dimethylnaphthalene (DMN) has been introduced as a ‘natural’ sprout inhibitor. Despite its effectiveness, the mode of action of DMN is unknown but it has been proposed that it acts by extending the natural period of tuber dormancy. In this study, the effects of DMN on dormancy-related hormone content and gene expression were analyzed in the commercial cultivar Russet Norkotah. These studies demonstrated that DMN does not act by extending the natural period of tuber dormancy but suppresses sprout growth in another yet unknown manner. The studies further show that DMN action is distinct from that of another synthetic sprout inhibitor chlorpropham which is widely used in the potato industry.
Technical Abstract: 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.