1021-4437/01/4804- $25.00 © 2001
Russian Journal of Plant Physiology, Vol. 48, No. 4, 2001, pp. 441–447. Translated from Fiziologiya Rastenii, Vol. 48, No. 4, 2001, pp. 514–522.
Original Russian Text Copyright © 2001 by Kenzhebaeva, Yamamoto, Matsumoto.
The presence of Al in acid soils disturbs many cell
functions and adversely affects plant growth and devel-
opment. Therefore, unraveling the plant responses that
are essential for plant tolerance to Al stress has been the
major goal of many recent studies [1, 2]. The rapid inhi-
bition of root growth, an early indicator of the toxic Al
effect, has been unquestionably related to arrested cell
elongation , enhanced lignin deposition , and
changes in the polysaccharide contents  in the cell
wall. Yet, there have been few studies of the glycopro-
tein response to Al, although these proteins are essen-
tial structural and enzymic components of the cell wall.
The structural proteins of primary cell walls com-
prise three major classes , and the extensin family of
glycoproteins has been studied in the most detail.
Extensins are tyrosine-containing HRGPs forming the
threads of polyproline-II helical conformation, the back-
bone of the rigid protein molecule . The cell-wall
structural proteins of the monocot plant species have
been studied to a lesser extent than in the dicots [8, 9].
The genotype-speciﬁc mechanisms of tolerance and
sensitivity to Al have been studied for many years;
these studies were considerably promoted by the com-
parative investigation of wheat genotypes [10–14].
A hypothesis for the Al-evoked inhibition of root
elongation implies that the growth of cell walls is
arrested when the wall cannot expand any more
because of irreversible covalent interactions between
cell-wall components . However, the capacity of
the particular structural proteins to participate in main-
taining the rigid cell-wall structure has not been stud-
ied, although there exist data on the isolated and char-
acterized proteins, the putative key agents in cell
expansion, and the factors affecting the latter process
[16, 17]. The published evidence presumes that the oxi-
dative covalent binding of the structural proteins of the
primary cell wall is essential for the defense responses
of plant cells. The immobilization of the structural pro-
teins and an increase in the proportion of covalently
bound proteins was observed when plants were dam-
aged or infested by fungi at the successive phases of
plant development [18–21].
We presumed that the toxic Al effects are related to
glycoprotein redistribution in the cell wall. To test this
hypothesis, we isolated various glycoprotein fractions
from the puriﬁed cell walls of the Al-sensitive ES8 and
Al-tolerant ET8 wheat lines and determined the Al con-
tent in the root apices. The data thus obtained indicate
that the accumulation of characteristic polypeptides in
the extensin fraction isolated from the cell wall in the
Al-sensitive line was correlated with the Al-induced
inhibition of root elongation.
Aluminum-Induced Changes in Cell-Wall Glycoproteins
in the Root Tips of Al-Tolerant and Al-Sensitive Wheat Lines
S. S. Kenzhebaeva*, Y. Yamamoto**, and H. Matsumoto**
* Institute of Plant Physiology, Genetics, and Bioengineering, Ministry of Education and Science
and Academy of Sciences of Kazakhstan, ul. Timiryazeva 45, Almaty, 480090 Kazakhstan;
fax: (10327) 47-6106; e-mail: Saule.K@ippgb.academ.alma-ata.su
** Research Institute for Bioresources, Okayama University, Okayama, Japan
Received December 10, 1999
—To investigate wheat (
L.) responses to Al stress, KCl- and SDS-extracted glyco-
proteins (covalently bound proteins isolated by cell-wall digestion by cellulysine–pectolase mixture) and
extensins (hydroxyproline-containing glycoproteins, HRGPs) were isolated from cell-wall preparations puri-
ﬁed from the root apices of Al-sensitive and Al-tolerant near-isogenic lines ES8 and ET8. Under Al stress con-
ditions, two lines differed mostly in their extensins. The untreated plants of two lines were low in covalently
bound extensins, although the content of this protein fraction in ES8 was higher than in ET8. When the seed-
lings were treated with Al, the extensin content increased in both wheat lines and especially in the Al-tolerant
ET8 plants. Using two-dimensional electrophoresis, the authors demonstrated the accumulation of polypeptides
with mol wts of 22.2 kD (pI 5.5–6.5), 24.5 kD (pI 5.8–6.0), and 33.1 kD (pI 5.25) and polypeptides of 22.2 kD
(pI 6.8–7.6) and 40.5 kD (pI 7.6) in the extensin fraction from the cell walls of the Al-sensitive plants. The reg-
ulation of cell responses to Al stress may involve extensin expression.
Key words: Triticum aestivum - Al-induced stress - cell wall proteins - root tips
: CBP—covalently bound proteins; HRGPs—
hydroxyproline-rich glycoproteins; IPG—immobilized pH gradi-
ent; RRE—relative root elongation.