Distribution of ATPase activity at the host-pathogen interfaces of rust infections

Phosphatase activities have been localised cytochemically at haustorial-host interfaces of spermogonial-aecial and uredinial stages of Puccinia punctiformis, the monokaryotic phase of P. menthae and dikaryotic infections of Uromyces vicia-fabae. ATPase activity, similar to that of the wall-lining plasmalemma of the host cell, was associated with the extrahaustorial membrane of the filamentous monokaryotic (M-) haustoria of the spermogonial-aecial infections but not with the dikaryotic (D-) haustoria of the uredinial infection. In P. menthae, ATPase activity associated with the extrahaustorial membrane decreased towards the distal region of M-haustoria, as previously reported for P. poarum [35]. This supports the hypothesis that, in some cases, the membrane enclosing the apical portion of M-haustoria transiently resembles the extrahaustorial membrane of D-haustoria, whereas that adjacent to older, proximal regions is functionally similar to the remainder of the host plasmalemma. ATPase activity was recorded at the fungal plasmalemma of both M- and D-haustoria of P. punctiformis but not in P. menthae. These results are in accord with the established view that the filamentous haustoria of the monokaryon are physiologically, as well as morphologically, less specialized than those of the dikaryon.