Temporal and spatial regulation of glucomannan deposition and mobilization in corms of Amorphophallus konjac (Araceae)

Abstract

Konjac glucomannan (KGM), the main biologically active constituent of konjac flour extracted from corms of Amorphophallus konjac (konjac), has potential to be used as a nutraceutical (satiety agent) to combat obesity. Here we present the results of an immunocytochemical investigation of the developmental regulation of the deposition and mobilization of glucomannan in corm tissues of konjac, using an antiheteromannan (mannan/glucomannan) antiserum. The intensity of antibody binding to glucomannan idioblasts at six developmental stages (i.e., dormancy, leaf bud emergence, leaf bud elongation, leaflet emergence, leaf expansion, and shoot senescence) was compared. A temporally regulated pattern of glucomannan deposition and mobilization within the glucomannan idioblasts was observed. A source-sink transition in the corm was shown to occur after leaflet emergence, prior to complete expansion of the leaves. Our data also suggest that the mobilization of KGM initiates at the periphery of the corm and proceeds inward toward the center of the corm. This study represents a significant milestone in our understanding of the mechanisms involved in the physiological and biochemical control of KGM biosynthesis, partitioning, storage, and remobilization. Moreover, this information and the methodology presented provide valuable data for future improvement of the yield and productivity of this important crop.