1021-4437/04/5102- © 2004
Russian Journal of Plant Physiology, Vol. 51, No. 2, 2004, pp. 164–168. Translated from Fiziologiya Rastenii, Vol. 51, No. 2, 2004, pp. 184–189.
Original Russian Text Copyright © 2004 by Los.
Low-temperature induction of fatty acid (FA) desat-
urases in mesophilic organisms is a well-documented
phenomenon [1–3]. A drop in temperature is believed
to reduce membrane ﬂuidity, and FA desaturation in
membrane lipids permits a compensation of this pro-
cess, thus facilitating normal functioning of membrane-
bound energetic protein complexes [2–5]. The systems
of low-temperature signal transduction resulting in the
induction of desaturase genes were identiﬁed in meso-
[6–8] and Gram-
. They comprise
a sensor histidine kinase and the response regulator,
which is phosphorylated by this kinase.
The substrate induction of FA desaturases was
found only in mammalian cells [10–13] and yeast .
In the latter case, the addition of stearic acid to the cul-
ture medium accelerated transcription of
CoA desaturase. This effect was evidently related to the
active incorporation of saturated FA in membrane lip-
ids, which interfered the functioning of the respiratory
chains ; therefore, desaturation of such FA was nec-
The search for the controlling factors was so far
unsuccessful. However, in some organisms, DNA
-elements) were determined, which
might bind the proteins regulating transcription of the
desaturase genes [16, 17].
The goal of this work was to study the effects of low
temperature and stearic acid, a component of mem-
brane lipids and substrate for the desaturase, on tran-
scription of the
gene encoding the only FA desat-
urase in cells of the thermophilic cyanobacterium
MATERIALS AND METHODS
(IPPRAS B-453) was
obtained from the Collection of microalgae at the Insti-
tute of Plant Physiology RAS. Cells were grown at the
optimum temperature of 55
C, continuous illumination
from luminescent lamps (50–70
bubbling with a gas–air mixture containing 2% CO
RNA isolation and Northern blotting were per-
formed as described earlier [19, 20].
The determination of start points of transcription
was performed as described earlier  using synthetic
oligonucleotides SV1: 5'-AGGTCTGGGGTTC-
GAATTC and SV2: 5'-AATGGCCTTAGAAAAT-
GTCCT as primers for reverse transcription. In experi-
ments with primer extension, 5
g of total RNA per
reaction was used. Reverse transcription was per-
formed using SuperScriptII enzyme (New England
Biolabs, United States). Sequencing was performed
Low-Temperature and Substrate Induction of the Gene
9 Fatty Acid Desaturase in the Thermophilic
D. A. Los
Timiryazev Institute of Plant Physiology, Russian Academy of Sciences, Botanicheskaya ul. 35, Moscow, 127276 Russia;
fax: 7 (095) 977-9372; e-mail: email@example.com
Received June 16, 2003
—A decrease in ambient temperature induced the
gene encoding the only acyl-lipid desaturase
of thermophilic cyanobacterium
The addition of the substrate for this enzyme, stearic
acid (18:0), to the culture medium of cyanobacterium grown at optimum temperature also induced the
gene. At 55 and 45
C, gene transcription started at the position –59 upstream of the translation initiation codon.
After addition of 18:0, two speciﬁc pools of transcripts were detected. Some transcripts corresponded in size to
transcripts synthesized at 55 and 45
C, and other transcripts were longer. The determination of sites of the tran-
script synthesis initiation showed that 18:0 additionally induced transcription from positions –163 and –169.
These additional initiation sites were positioned within the coding sequence of the
gene preceding the
gene. Thus, at low-temperature and substrate induction, the expression of the
gene was evidently
controlled by different promoter sequences.
Key words: Synechococcus vulcanus - desaturases - low-temperature regulation - substrate regulation - gene
: FA—fatty acid(s).