Submitted to: American Society of Plant Physiologists Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 3/20/2000
Publication Date: N/A
Technical Abstract: Cytokinins have been implicated in the regulation of potato tuber dormancy. Levels of endogenous bioactive cytokinins are low during the initial period of dormancy and increase prior to the onset of sprout growth. Exogenous cytokinins are rapidly metabolized in both dormant and nondormant potato tubers. Preliminary studies have suggested two potential regulatory metabolic steps: side-chain oxidation to adenine derivatives catalyzed by cytokinin oxidase and N-glucosylation of isopentenyl-adenine (IP) or isopentenyl-adenosine (IPA) to the biologically inactive IP-9-glucoside. In order to determine the relative roles of these two metabolic processes in the regulation of cytokinin levels, we have developed an aseptic system using in-vitro generated potato microtubers which permits the feeding of both labeled cytokinins and potential metabolic inhibitors under defined conditions. In this system, exogenous [3H]-IPA is rapidly converted to several metabolites including: adenine/adenosine, IP, IP-9-glucoside and IPA-5'- monophosphate(IMP). Inclusion of an irreversible inhibitor of cytokinin oxidase results in a pronounced decrease in the conversion of IPA to adenine derivatives and a corresponding increase in the levels of IMP and IP-9-glucoside. The effects of other putative inhibitors of cytokinin oxidation and N-glucosylation are currently under investigation and these results will be discussed in relation to the regulation of cytokinin content during tuber dormancy.