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.