1021-4437/04/5102- © 2004
Russian Journal of Plant Physiology, Vol. 51, No. 2, 2004, pp. 198–202. Translated from Fiziologiya Rastenii, Vol. 51, No. 2, 2004, pp. 222–227.
Original Russian Text Copyright © 2004 by Rachenko, Rikhvanov, Varakina, Rusaleva, Borovskii, Voinikov.
A short-term pretreatment of organisms with mod-
erately elevated temperatures improves their tolerance
to subsequent more severe heating. This phenomenon
was called acquired or induced thermotolerance; it cor-
relates with the synthesis of Hsp, presuming a protec-
tive function of Hsp . Thus, the reliable evidence was
obtained that Hsp with a mol wt of 104 kD (Hsp104)
played a protective role in
cells . This protein did not prevent heat shock-
induced damages but helped cells recover after the ces-
sation of heating [3–5].
belongs to the family of
Hsp100/ClpB proteins. These proteins function also in
higher plants, but have not been found as yet in mam-
mals and humans .
deﬁcient in the
gene (a homolog of
were unable for the development of tolerance to lethal
heat shock, and the reverse transformation of the wild-
type gene restored this capacity. When the
was cloned in the cells of
S. cerevisiae hsp104
it restored yeast thermotolerance. Therefore, we sup-
pose that the mechanisms of heat shock tolerance are
common in higher plants and yeast .
In addition to high temperature, the synthesis of Hsp
can be also induced by chemical agents, such as heavy
metal ions, ethanol, analogs of amino acids, etc. .
Mitochondrial inhibitors might induce Hsp as well.
Thus, sodium azide and dinitrophenol are known to
induce heat shock puffs in polytene chromosomes of
salivary glands .
Earlier, we demonstrated that sodium azide
improved considerably the thermotolerance of
cells grown on glucose-containing medium. We
supposed that the protective action of sodium azide was
related to the induction of the synthesis of Hsp104 .
To verify this hypothesis, we compared here the effects
of sodium azide on basic and induced thermotolerance
in the wild-type strain and the
We also monitored the effect of this inhibitor
on the synthesis of Hsp104 during heat shock.
MATERIALS AND METHODS
We used two strains of yeast
-74-D694 (wild type) and a mutant deﬁcient in
gene expression (mutant was obtained from
Prof. S. Lindquist (Chicago University, United States)).
Yeast culture was maintained on solidiﬁed YEPD (5 g/l
yeast extract, 10 g/l peptone, 20 g/l glucose, and 15 g/l
Yeast were grown for 14–16 h at 30
C in 100-ml
ﬂasks containing 25 ml of liquid YEPD or YEPGal
(with glucose replaced by the equivalent amount of
galactose) to the density of 10
In order to study the effect of preliminary treatment
with sodium azide on yeast thermotolerance, we added
0.15 mM NaN
to the cell suspension and incubated it
for 30 min at 30
C. To remove the inhibitor, cells were
The Effect of Sodium Azide on Basic and Induced
E. I. Rachenko, E. G. Rikhvanov, N. N. Varakina, T. M. Rusaleva,
G. B. Borovskii, and V. K. Voinikov
Siberian Institute of Plant Physiology and Biochemistry, Siberian Division, Russian Academy of Sciences,
ul. Lermontova 132, Irkutsk, 664033 Russia;
fax: 7 (3952) 51-0754; e-mail: eugene@siﬁbr.irk.ru
Received January 5, 2003
—The action mechanism of the mitochondrial inhibitor sodium azide on thermotolerance in
was studied. At ambient growth temperature, pretreatment with sodium azide was shown to
improve the thermotolerance of parent cells and the
mutant. Treating with the inhibitor during a mild
heat shock suppressed the development of induced thermotolerance due to the inhibition of heat shock protein
(Hsp104) synthesis. Treating with the inhibitor immediately before lethal heat shock produced a variety of
effects on thermotolerance depending on whether the yeast metabolism was oxidative or fermentative. The con-
clusions are: (1) the protective effect of sodium azide on the thermotolerance of
cells grown on
glucose-containing medium is not related to Hsp104 functioning, and (2) the mechanisms of basic and induced
thermotolerance differ considerably.
Key words: Saccharomyces cerevisiae - sodium azide - basic and induced thermotolerance - HSP104
: Hsp—heat-shock protein(s); YEPD—yeast
extract, peptone, dextrose (glucose).