ISSN 1021-4437, Russian Journal of Plant Physiology, 2008, Vol. 55, No. 1, pp. 82–92. © Pleiades Publishing, Ltd., 2008.
Lignins are complex racemic aromatic heteropoly-
mers mainly present in secondary thickened plant cell
walls and are indispensable for plant structure and
defense . Lignins support the structural integrity of
the cell wall and stiffness and strength of the stem. Fur-
thermore, lignins make the cell wall waterproof, thus
directing the transport of water and solutes through the
vascular system, and play a role in protecting plants
against pathogens [2–4]. The ability to synthesize
lignins has been essential in the evolutionary adaptation
of plants from an aquatic environment to terrestrial hab-
Lignins are derived mainly from three hydroxycin-
namyl alcohol monomers,
-coumaryl, coniferyl, and
sinapyl alcohols, differing in degree of methoxylation.
These monolignols produce
cyl, and syringyl phenylpropanoid units, respectively,
Abbreviations: C3H—p-coumarate 3-hydroxylase; C4H—cin-
namate 4-hydroxylase; ORF—open reading frame; RACE—
rapid ampliﬁcation of cDNA ends; RT-PCR-reverse transcrip-
This text was submitted by the authors in English.
when incorporated into the lignin polymer. Besides
these three monolignols, other phenylpropanoids are
also present in the polymer, including hydroxycinnamyl
aldehydes, hydroxycinnamyl acetates, hydroxycinnamyl
hydroxycinnamate esters, etc. [1, 2, 5].
Lignin composition depends on taxa, cell types, and
developmental and environmental conditions . Hard-
wood lignins in dicotyledonous angiosperms consist
mainly of G and S units with a small amount of H units,
whereas softwood lignins in gymnosperms consist
mainly of G units with low proportion of H units. Grass
lignins contain comparable amounts of G and S units
and more H units than dicots .
Although lignins have been studied for over a cen-
tury, many aspects of its biosynthesis have not yet been
understood. The monolignol biosynthetic pathway has
been rewritten many times, and the exact route toward
the monolignols remains a matter of debate [1, 2, 7, 8].
Until now, however, metabolic channeling has only
been demonstrated from phenylalanine to
involving a microsomal phenylalanine ammonia-lyase
isoform [2, 9].
A New Gene Coding for
, Z. Deng
, S. Gao
, X. Sun
, and K. Tang
State Key Laboratory of Genetic Engineering, School of Life Sciences, Fudan University, 220 Hundan Road,
Shanghai 200433, China;
fax: 86-21-65643552; e-mails: firstname.lastname@example.org or email@example.com
Plant Biotechnology Research Center, School of Agriculture and Biology, Shanghai Jiao Tong University,
Shanghai 200030, China
Received August 7, 2006
-Coumarate 3-hydroxylase (C3H) is a rate-limiting enzyme involved in monolignol biosynthesis.
The full-length cDNA from
and genomic DNA sequence encoding C3H (designated as
were cloned and characterized for the ﬁrst time by rapid ampliﬁcation of cDNA ends technique. The full-length
was of 1860 bp containing a 1527 bp open reading frame encoding a cytochrome P450 protein
of 508 amino acids with a calculated mol wt of 57.46 kD and an isoelectric point of 7.09. Two introns were
present in the
gene. Comparative and bioinformatic analyses revealed that GbC3H had close similarity
with C3Hs from other species and contained a conserved cytochrome P450 cysteine heme-iron ligand signature.
Phylogenetic analysis indicated that GbC3H shared a common evolutionary origin based on sequence and had
the closest relationship to C3H from gymnosperm species. Southern blot analysis indicated that
belonged to a small-gene family. Tissue expression pattern analysis revealed the highest expression of
in roots followed by leaves, and no expression was detected in stems. Only a few proteins of this class have been
found, so the cloning and characterization of
will be useful in understanding the role of C3Hs in the
lignin biosynthesis at the molecular level.
Key words: Ginkgo biloba - C3H - rapid ampliﬁcation of cDNA ends - lignin