STRUCTURE, FUNCTION, AND, MOTILITY OF VACUOLES IN FILAMENTOUS FUNGI

Current information on the structure and function of motile tubular va cuoles in Pisolithus tinctorius and other fungi is reviewed, The use o f fluorochromes to label the vacuole lumen is evaluated and observatio ns on the structure and motility of vacuoles in P. tinctorius are diff erentiated from possible artifacts. The styryl dyes FM4-64 and MDY-64, used in yeast to demonstrate endocytosis, show little or no labeling of internal membranes in undamaged P, tinctorius cells. This agrees wi th our data showing that other probes for endocytosis such as Lucifer yellow CH are not taken up by hyphal tip cells. Overall, the observati ons do not support endocytosis in hyphal tips. It has been suggested t hat tubular vacuole systems carry out longitudinal transport, and evid ence in favor of this hypothesis is evaluated. New data are presented to show that many of the large vacuoles in subapical cells are attache d to the plasma membrane and are relatively immobile, while video sequ ences show movement of fluorochrome in pulses along a series of severa l large vacuoles, all interconnected via tubules, Tubular vacuoles fro m thick sections of hyphae processed under anhydrous conditions are sh own by X-ray microanalysis to contain relatively high levels of P and K, as seen previously in the larger vacuoles. These results provide fu rther evidence for a role of the tubular vacuoles in longitudinal tran sport of P. (C) 1998 Academic Press.