Introduction to Fungi, Third Edition

130 CHY TRIDIOMYCOTA
Fig 6.2 Flagellar apparatus typical of zoospores of Chytridiomycota. (a) Median longitudinal section of the junction of the flagellum
with the body of the zoospore.The labels indicate the flagellum proper (F), transitional zone (TZ), kinetosome (K), electron-dense
region (ED), concentric fibres (CF), transitional fibres (TF), kinetosome props (KP), terminal plate (TP), kinetosome (K) showing a
cartwheel-like organization (Cw), dormant kinetosome (DK), fibrillar material (Fi) found in some taxa, and microtubular roots (Mt)
extending from the side or end of the kinetosome into the body of the zoospore. (b) Transverse section near the terminal plate
showing nine kinetosome props extending from doublet microtubules to the cell membrane. (c) Transverse section in the lower
part of the transition zone showing concentric and transitional fibres. (d) Transverse section of the flagellum proper showing two
central microtubules and nine peripheral doublet microtubules enclosed in the flagellar membrane (FM). (e) Schematic drawing of
the flagellum proper in transverse section.The arrowed line 0° 180° shows an imaginary plane which coincides with the plane of
undulation of the flagellum, passing through doublet pair1and between the central microtubules and doublet pairs 5 and 6.
The convention used in labelling the outer doublet pairs of microtubules is shown: the microtubule with dynein arms (d) is the
A microtubule and its partner is the B microtubule. (f) Kinetosome in transverse section showing the triplet arrangement of the
peripheral microtubules by the addition of a third microtubule (C). Redrawn from Barr and De¤saulniers (1988) by copyright
permission of the National Research Council of Canada, Barr (1992). ßThe Mycological Society of America, and D. J. S. Barr (2001)
with kind permission of Springer Science and Business Media.
the two central microtubules arise near a
terminal plate. The structure of the flagellum
and kinetosome in transverse section is shown in
Figs. 6.2e and f (Barr & Désaulniers, 1988).
The microbody lipid complex
The MLC (Fig. 6.3) is made up of a microbody
which is often closely appressed to a large lipid
globule and to simple membrane cisternae or
a tubular membrane system, the rumposome.
This is defined as a cisterna in which there is an
area with hexagonally arranged, honeycomb-like
pores called fenestrae (Fuller, 1976; Powell &
Roychoudhury, 1992). The rumposome may
be involved in signal transduction from the
plasma membrane to the flagellum because it
is known that this organelle sequesters calcium.
Regulation of external calcium concentrations
has an effect on the symmetry of flagellar beat
and hence on the direction of zoospore movement
(Powell, 1983).
There are several distinct types of MLC (Powell
& Roychoudhury, 1992) and Fig. 6.3 illustrates
diagrammatically just one of them, that
described for Rhizophlyctis harderi. In this species,
the MLC includes several (3 5) lipid globules.