I. Slaninova et al., Cell wall and cytoskeleton reorganization as the response to hyperosmotic shock in Saccharomyces cerevisiae, ARCH MICROB, 173(4), 2000, pp. 245-252
Transfer of exponentially growing cells of the yeast Saccharomyces cerevisi
ae to hyperosmotic growth medium containing 0.7-1 M KCl, 1 M mannitol, and/
or 1 M glycerol caused cessation of yeast growth for about 2 h; thereafter,
growth resumed at almost the original rate. During this time, formation of
fluorescent patches on the inner surface of cell walls stained with Primuli
n or Calcofluor white was observed. The fluorescent patches also formed in
solutions of KCl or when synthesis of the cell wall was blocked with cycloh
eximide and/or 2-deoxyglucose. The patches gradually disappeared as the cel
ls resumed growth, and the new buds had smooth cell walls. Electron microsc
opy of freeze-etched replicas of osmotically stressed cells revealed deep p
lasma membrane invaginations filled from the periplasmic side with an amorp
hous cell wall material that appeared to correspond to the fluorescent patc
hes on the cell surface. The rate of incorporation of D-[U-C-14]glucose fro
m the growth medium into the individual cell wall polysaccharides during os
motic shock followed the growth kinetics. No differences in cell wall compo
sition between osmotically stressed yeast and control cells were found. Hyp
erosmotic shock caused changes in cytoskeletal elements, as demonstrated by
the disappearance of microtubules and actin microfilaments. After 2-3 h in
hyperosmotic medium, both microtubules and microfilaments regenerated to t
heir original polarized forms and the actin patches resumed their positions
at the apices of growing buds. The response of S. cerevisiae strains with
mutations in the osmosensing pathway genes hog1 and pbs2 to hyperosmotic sh
ock was similar to that of the wild-type strain. We conclude that, besides
causing a temporary disassembling of the cytoskeleton, hyperosmotic shock i
nduces a change in the organization of the cell wall, apparently resulting
from the displacement of periplasmic and cell wall matrix material into inv
aginations of the plasma membrane created by the plasmolysis.