Ultrastructure of Sexual Reproduction of Monascus purpureus

Cleistothecia of Monascus purpureus were initiated by formation of antheridia and ascogonia. A trichogyne protruded from the ascogonium and fused with the antheridium. Dichotomously branching ascogenous hyphae arose from the ascogonium and were covered by anastomosed flattened sterile hyphae from the stalk of the ascogonium. Crozier formation was followed by typical ascus development. Cellular structures within the centrum of the cleistothecium were wall-less with occasional exceptions. Typical ascospore-delimiting double membranes were formed interior to the ascus plasma membrane and developed toward the center of the ascus to delimit the ascospores. Sterile structures within the centrum became vacuolate, probably nourishing the asci and ascospores. Mature cleistothecia contained numerous smooth-walled ascospores protected only by the outer cell wall of the peridium.