Use of D-glucose-fenpiclonil conjugate as a potent and specific inhibitor of sucrose carriers.

Until now, specific inhibitors of sucrose carriers were not available. This led us to study the properties of the recently synthesized D-glucose-fenpiclonil conjugate (D-GFC). This large amphiphilic glucoside exhibited an extremely low phloem systemicity in contrast to L-amino acid-fenpiclonil conjugates. Using Ricinus seedlings, the effect of D-GFC on 0.5 mM [C-14] sucrose (Suc), 3-O-[H-3] methylglucose, and [H-3] glutamine uptake by cotyledon tissues was compared with that of p-chloromercuribenzenesulfonic acid (PCMBS). D-GFC dramatically inhibited H+-Suc symport at the same concentrations as PCMBS (0.5 and 1 mM), but in contrast to the thiol reagent, it did not affect 3-O-methylglucose and glutamine transport, nor the acidification of the incubation medium by cotyledon tissues. Similarly, 0.5 mM D-GFC inhibited active Suc uptake by Vicia faba leaf tissues and by Saccharomyces cerevisiae cells transformed with AtSUC2, a gene involved in Suc phloem loading in Arabidopsis, by approximately 80%. The data indicated that D-GFC was a potent inhibitor of Suc uptake from the endosperm and of Suc phloem loading. It is the first chemical known to exhibit such specificity, at least in Ricinus, and this property