1021-4437/01/4804- $25.00 © 2001
Russian Journal of Plant Physiology, Vol. 48, No. 4, 2001, pp. 464–466. Translated from Fiziologiya Rastenii, Vol. 48, No. 4, 2001, pp. 542–544.
Original Russian Text Copyright © 2001 by Nikolaeva.
O-Methyltransferase (OMT; EC 188.8.131.52) catalyzes
the methylation of various phenolic compounds using
S-adenosyl-L-methionine as a donor of methyl groups.
In plants, there are two main types of OMT, lignin-spe-
ciﬁc and ﬂavonoid-speciﬁc ones. The former enzyme
takes part in the formation of lignin precursors, that is,
O-methylated cinnamic acids, and the latter performs
the methylation of various phenolic compounds. There-
fore, OMTs are usually designated as caffeoyl-OMT
and ﬂavonoid-OMT . The ﬁrst catalyze the methyla-
tion of caffeic and 5-hydroxyferulic acids with the for-
mation of ferulic (4-hydroxy-3-methoxycinnamic) and
sinapic (4-hydroxy-3,5-dimethoxycinnamic) acids.
The reduction of ferulic and sinapic acids yields
coniferyl and sinapyl alcohols, respectively. These
alcohols are direct substrates for the precursors of lig-
nin monomers in the process of polymerization cata-
lyzed by peroxidase . According to the nature of
their component monomers, the lignins are divided into
gymnosperm (guaiacyl) lignin formed from coniferyl
alcohol and angiosperm (guaiacyl-syringyl) lignin
formed by co-polymerization of coniferyl and sinapyl
Lignin is the most important component of the cell
walls of vascular plants endowing plant organs and tis-
sues with mechanical rigidity. Because of the insolubil-
ity and a complex structure of the lignin polymer, it is
resistant to degradation by most microorganisms .
Moreover, the rapid formation of lignin as a response to
mechanical damage or an attack by pathogens repre-
sents one of the mechanisms of plant defense .
At present, all stages of lignin biosynthesis and the
enzymes of this biosynthesis are established as a whole.
However, the mechanisms controlling the quality and
quantity of the lignin formed are as yet unknown.
As mentioned above, the structure of lignin poly-
mers both in gymnosperm and angiosperm plants is
based on methoxylated alcohols. OMT is responsible
for the methylation stage, and therefore this enzyme
plays one of the key roles in the lignin biosynthesis .
According to recent evidence, the expression of
OMT is accompanied by the appearance of most of its
transcripts in vascular tissues, in which lignin is mainly
accumulated [5, 6]. At the same time, the problem of
the limiting role of OMT in the regulation of the ligni-
ﬁcation process remains unsolved so far, because the
known facts are rather contradictory. Thus, experiments
using bamboo seedlings showed that an increase in the
accumulation of lignin was accompanied by a parallel
increase in the OMT activity , whereas a decrease in
the content of lignin in mutant maize seedlings was
related to its lowered activity . At the same time, in
poplar  and tea  plants, there was no direct cor-
relation between the lignin accumulation and the OMT
The objective of this work was the elucidation of a
relationship between the OMT activity and the content
of lignin in various organs of kidney bean plants.
MATERIALS AND METHODS
Twelve- to 14-day-old kidney beans
L., cv. Saksa) were used in the
experiments. They were grown on Perlite in a phytotron
environment-controlled chamber, at a temperature
On the Relationship between the Activity of O-Methyltransferase
and the Content of Lignin in Various Organs of Kidney Bean
T. N. Nikolaeva
Timiryazev Institute of Plant Physiology, Russian Academy of Sciences,
Botanicheskaya ul. 35, Moscow, 127276 Russia; fax: 7 (095) 977-8018; e-mail: email@example.com
Received March 21, 2000
—The activity of O-methyltransferase (OMT) and the content of lignin in various organs of 12-
to 14-day-old seedlings of kidney bean (
L., cv. Saksa) were determined. The epicotyl and
hypocotyl were characterized by the highest OMT activity, and the leaves, by the lowest OMT activity. At the
same time, the lignin content gradually increased in the following order: leaves < epicotyl < hypocotyl < roots.
Thus, in kidney bean seedlings, there is no direct relationship between the OMT activity and the lignin content.
It is suggested that lignin biosynthesis is limited by biosynthetic steps other than O-methylation of caffeic and
5-hydroxyferulic acids affected by OMT.
Key words: Phaseolus vulgaris - O-methyltransferase - lignin
: OMT—O-methyltransferase; SAM—S-adenosyl-