Polyoxin-B-treated and untreated (control) hypae of
Alternaria kikuchiana Tanaka were first degraded with 2N NaOH, 1N H
2SO
4, and digestive enzymes, and then morphological alterations of the cell walls were investigated by cytochemical methods and electron microscopy. A pronounced difference between control and treated hyphae was seen after sequential treatment with NaOH-H
2SO
4-NaOH. Inner wall layers of controls were transformed into numerous microfibrils; these were identified, in turn, by chitinase and Lytic enzyme digestions as chitin and β-1, 3-glucan intermixed with protein. But these same treatments failed to structurally degrade the walls of polyoxin-treated hyphae. In the controls, only the thin outer wall layer showed any resistance to the treatment, but in polyoxin-treated hyphae the entire cell wall, including septae and walls of intracellular hypha, was resistant to a sequence of the degradative treatments. Cytochemical tests revealed that both control and polyoxin-treated hyphae, which originally contained chitin, no longer responded positively to tests for chitin after chitinase or HCl treatment following treatment with the NaOH-H
2SO
4-NaOH sequence. This study suggests two possibilities i) cell walls, especially inner wall layers, of control and polyoxin-treated hyphae may have different structural constituents, and ii) melanin-like pigments in inner cell walls may be associated with the resistance of polyoxin-treated hyphae to lysis by digestive enzymes.
View full abstract