Abstract
Electrofusion of Pleurotus cornucopiae protoplasts was conducted using the glass electrode electrofusion technique in which a pair of protoplasts was put into contact under a microscope and an electrical pulse was applied. Initially, the protoplast of the basidiomycete was too small for the glass electrode, but after incubation in a mixture of cell lytic enzymes, it increased in size into a giant protoplast. In screening studies of natural compounds effective in inducing fruiting body development in Pleurotus ostreatus on agar medium, a triterpenoid saponin was found to exert a hormone-like effect. In order to study the structure-activity relationship, a betulin glycoside was synthesized by linking a sugar moiety to a triterpenoid betulin derived from the outer bark of Betula platyphylla. The sugar chain was further lengthened by transglycosylation using chemical and enzymatic reactions. Betulin with added sugar moieties induced fruiting activity in Pleurotus ostreatus; this fruiting activity correlated with the sugar length. In addition, 3-O-alkyl-D-glucose (AG), a novel hydrophobic compound with an attached sugar chain that has been proposed to trigger fruiting in P. ostreatus, was synthesized; AG with an eight-carbon alkyl chain was shown to effectively induce P. ostreatus fruiting bodies. Thus, it was proven for the first time that a sugar-containing amphipathic compound could stimulate fruiting body development.
