ISSN 10214437, Russian Journal of Plant Physiology, 2013, Vol. 60, No. 3, pp. 396–403. © Pleiades Publishing, Ltd., 2013.
Ubiquitous enzymes, such as chitinases, are widely
present in bacteria, fungi, animals, and plants. They
catalyze the hydrolytic cleavage of the
sidic bonds between biopolymer Nacetylglu
cosamine residues from the chitin molecule, which is
a major structural component of fungal cell walls,
exoskeleton of insects, and crustacean shells [1, 2].
Based on the hydrolytic sites, chitinases can be divided
into two categories, exochitinases and endochitinases
. The cleavage sites of exochitinases are in the
reducing or nonreducing end of the chitin chain, while
endochitinases cleave randomly .
Chitinases exhibit diverse functions in various spe
cies. Bacteria acquire nutrition from the degradation
of chitinous substrates by chitinases . In fungi,
chitinases participate in remodeling the cellwall
structure, which in turn affects cell morphology . It
has been shown that insect chitinases play a major role
in the degradation of the old cuticle and the peri
This text was submitted by the authors in English.
These authors contributed equally to this work.
trophic matrix for growth, maturation, and repair .
Plant and animal chitinases act as defense proteins
responding to pathogenic attacks . Furthermore,
other events involved in the growth and development
processes, such as pollination, seed germination, and
somatic embryogenesis cannot be completed without
the participation of chitinases .
Just as in the case of other plant enzymes , genes
encoding plant chitinases belong to a large gene family
and are organized in five classes (Classes I–V), which
are different in both structure and mechanism. Classes
I, II, and IV are comprised of glycoside hydrolase fam
ily 19, whereas Classes III and V belong to glycoside
hydrolase family 18 [8, 10]. Glycoside hydrolase fam
ily 18 is distributed in various organisms and may have
adopted a substrateassisted catalysis mechanism.
Glycoside hydrolase family 19 is almost exclusively
present in plants and expresses an acid/base mecha
nism [10, 11]. The Class I chitinases are found in both
monocots and dicots, while classes II and IV are found
mainly in dicots . Plant chitinases exist in all
organelles and tissues, including the apoplast and vac
uole . They can be induced by various stressors,
such as elicitor, wounding, and plant hormones .
Many chitinase genes from various plant species were
cloned, and their influence on resistance to abiotic
Cloning and Expression Analysis of Chitinase Genes
, J. Song
, R. Huang, M. Huang, and L. Xu
Jiangsu Key Laboratory for Poplar Germplasm Enhancement and Variety Improvement,
Nanjing Forestry University, Nanjing, 210037, China;
fax: +862585427882; emails: email@example.com; firstname.lastname@example.org
Received July 11, 2012
—Plant chitinases play a key role in conferring resistance to environmental stresses, including attack
by fungal pathogens. In the present study, we employed rapid amplification of cDNA ends (RACE) to iden
tify five chitinase genes in
Moench. Sequence alignment revealed that these genes belong
to five subfamilies of chitinase genes. The fulllength cDNAs of these genes ranged in size from 991 to
1358 bp and encoded proteins with mol wts from 29.5 to 40.3 kD. Five genes were grouped into three major
clades based on amino acid sequences of encoded proteins. Exon–intron gene structure and protein domain
analysis further supported the designation. A threedimensional structure comparison showed the high sim
ilarity between five
chitinases and three wellstudied chitinases from other species. The expres
sion levels of all five genes were upregulated during
infection with the pathogenic fungus
, and four of them were highly induced by salt and drought stresses. Furthermore, such factors as elic
itors, wounding, and low temperature also elevated the expression of these chitinase genes to varying extents.
We postulated that these chitinase genes may be involved in pathways of the defense against fungal infection
and function in response to various abiotic stresses.
Keywords: Populus canadensis, Marssonina brunnea
, biotic stress, fulllength cDNA cloning, gene expression,
: CTAB—cetyltrimethylammonium bromide;
RACE—rapid amplification of cDNA ends; RTPCR—reverse
transcription–polymerase chain reaction.