Host–parasite relations in mycoparasite. II. Incorporation of tritiated N-acetyl-glucosamine into Choanephora cucurbitarum infected with Piptocephalis virginiana
The mature spore of Choanephora cucurbitarum possesses a thick three-layered cell wall which is different from the hyphal wall. Its germination is accompanied by the formation of a thin, elastic inner layer which extends around the emerging germ tube and the growing hypha. High resolution autoradiography showed that 3H N-acetyl-glucosamine, a precursor of chitin, was incorporated preferentially in the thin inner layer of the conidial wall and also in the wall of the growing hypha. When the label was fed to the infected cells, at different intervals, 18, 24, 30 h after inoculation, grains were observed in the sheath area around the haustorium of Piptocephalis virginiana, only at 24 and 30 h after inoculation. The significance of these results in relation to the origin and composition of the haustorial sheath is discussed.