DEOXYMANNOJIRIMYCIN INHIBITS DE-NOVO SYNTHESIS OF COMPLEX N-GLYCANS AND DELAYS TOMATO FRUIT RIPENING

Unconjugated N-glycans (UNGs) of the high mannosyl-type extracted from tomato fruit delay ripening of fruit pericarp discs by 2 days when ap plied exogenously. Since the amount of high mannosyl-type UNGs decreas es while the amount of complex-type UNGs increases during early ripeni ng, we postulated that high mannosyl UNGs are converted to complex-typ e by Golgi enzymes to relieve inhibition of ripening-inhibition by the high mannosyl-type UNGs. In this paper, we investigated the effect of deoxymannojirimycin, an inhibitor of mannosidase I involved in comple x N-glycan synthesis. Deoxymannojirimycin, applied to pericarp discs, both inhibited synthesis of complex-type N-glycans and delayed ripenin g, supporting our hypothesis on modulation of tomato ripening by UNGs.