S. Mizuta et al., STRUCTURE AND ASSEMBLY OF THE CORTICAL MICROTUBULE CYTOSKELETON IN THE GREEN-ALGA, BOODLEA-COACTA, Protoplasma, 189(1-2), 1995, pp. 113-122
Examination was made of the structure and assembly of the cortical mic
rotubule (MT) cytoskeleton in the coenocytic green alga Boodlea coacta
(Dickie) Murray et De Toni by immunofluorescence microscopy. Cortical
MTs in Boodlea protoplasts are arranged randomly bur some show a meri
dional arrangement within 6 h after protoplast formation. At 6-9 h suc
h MTs become highly concentrated and parallel to each other in certain
areas. At 12 h the concentration is uniformly high throughout the cel
l, indicating the completion of high density meridional arrangement of
cortical MTs. Cortical MTs exhibiting a high density, meridional arra
ngement show characteristics disassembly by treatment with 10 mu M ami
prophos-methyl (APM) or cold treatment (0 degrees C). Disassembly occu
rs by each MT unit at positions skipping 30-40 mu m in the transverse
direction. and neighboring MTs subsequently disassemble to form MT gro
ups. Each group becomes slender and then disappears completely within
the following 24 h. The meridional arrangement of cortical MTs is disr
upted by N-ethylmaleimide (NEM) accompanied by a remarkable reduction
in density. The remaining MTs form groups at 30-40 mu m intervals from
each other, as also occurs with drug or cold treatment, but disruptio
n and density return to normal levels following removal of NEM. It app
ears that there are meridionally oriented channels, anchor-rich and an
chor-poor, in the plasma membrane. The channels could be distributed a
lternately and anchors could be deposited in a cross-linking manner wi
th cortical MTs to form a stable cortical MT-cytoskeleton. MTs compris
ing the cortical MT cytoskeleton could be oriented by meridionally ori
ented channels of anchors which are distributed following establishmen
t of cell polarity.