1021-4437/02/4906- $27.00 © 2002
Russian Journal of Plant Physiology, Vol. 49, No. 6, 2002, pp. 792–798. Translated from Fiziologiya Rastenii, Vol. 49, No. 6, 2002, pp. 890–897.
Original Russian Text Copyright © 2002 by Zabotin, Barysheva, Troﬁmova, Lozovaya, Widholm.
-1,3-glucane) is a cell-wall polysaccha-
ride that is essential for plant activities, although its
content in plant tissues is negligible. Callose is synthe-
sized in the course of plant development and at the par-
ticular stages of cytokinesis; however, its accumulation
is usually transitory. Thus, callose was found in devel-
oping cotton ﬁbers , growing pollen tubes , grow-
ing and obliterated sieve tubes , and emerging cell
plates in dividing meristematic cells [4, 5]. Callose is a
component of plasmodesmata and participates in the
control of the transport along them ; on the other
hand, callose produces a physical barrier that restores
plant cell integrity when damaged by various factors,
including a pathogen attack [7–11].
Callose synthesis and degradation are run by a sys-
tem of enzymes, and their locations and activities are
determined by the patterns of plant growth and devel-
opment and plant defense response to various stress
agents and pathogens.
[12–16] carried out the most consistent
studies of callose biosynthesis. Their evidence is
summed up in the following way: the compound is syn-
thesized by callose synthase located in plasma mem-
brane in such a way that the substrate, UDP-glucose,
arrives from the cytoplasm, and the product callose is
deposited in the extracellular matrix . The synthase
activity depends on the phospholipids surrounding the
enzyme [12, 14] and is not mediated by calmodulin
. Calcium was shown to play a leading role in initi-
ating callose synthesis [7, 13, 15], yet callose biosyn-
thesis can be initiated in a Ca-independent way, by
trypsinization  or spirostanol treatment . Wald-
 presumed that, in addition to calcium,
other endogenous regulators are essential for
callose synthesis, such as
located in the vacuole; redistribution of these additional
factors between the vacuole and cytoplasm affects the
transduction pathway of callose synthesis .
The short life span of callose molecules suggests
that callose metabolism is shifted towards callose
catabolism. This idea is supported by the observations
that glucanase activities are enhanced under conditions
promoting callose accumulation.
-1,3-Glucanases, or laminarinases (EC 188.8.131.52)
-1,3-glucanes, such as laminarin, and are
widely distributed in bacteria, fungi, algae, higher
plants, and some invertebrates . There are two
forms of these enzymes: endo- and exoglucanases.
As a whole, the glucanases perform diverse func-
tions: their activities change in the course of plant
development and are promoted by plant hormones [7,
20] and pathogens ; they participate in glucan deg-
radation in germinating seeds [22, 23], in cell elonga-
tion , in pollen tube growth , and in callose deg-
radation in sieve tubes [25, 26].
While callose synthesis and activation of
canases as the partial response of plant cells to patho-
gen attacks are well known [7, 21], the coupling of the
enzymes participating in callose metabolism in the
morphogenetic events, such as cell plate formation, has
not been established .
Therefore, the objective of the present study was to
follow the time-course of callose content and the
enzyme activities of callose metabolism in order to ﬁnd
out whether they are involved in the suspension cell
growth and to investigate the speciﬁc activation of cal-
Regulation of Callose Metabolism in Higher Plant Cells
A. I. Zabotin*, T. S. Barysheva*, O. I. Trofimova*, V. V. Lozovaya*, and J. Widholm**
*Kazan Institute of Biochemistry and Biophysics, Kazan Scientiﬁc Center, Russian Academy of Sciences,
post box 30, Kazan, 420503 Russia;
**University of Illinois, Urbana–Champaine, United States
Received July 23, 2001
—Temporary accumulation of callose in suspension-cultured wheat (
cells at the exponential growth phase was correlated with the mitotic index due to the formation of the cell plates
in dividing cells. Callose disappeared in expanding cells owing to enhanced activities of endo- and exogluca-
nases. The exogluconase activity was reduced when the cells were treated with cycloheximide, an inhibitor of
protein synthesis. A similar pattern was observed when elicitors experimentally enhanced callose synthesis.
Apparently, in such cases, callose behaves as a temporary component repairing the cell wall. We presume that
plant cells comprise a universal mechanism for regulating callose synthesis.
Key words: Triticum timopheevii - suspension culture - callose - glucanases - cycloheximide