ISSN 10214437, Russian Journal of Plant Physiology, 2012, Vol. 59, No. 1, pp. 97–104. © Pleiades Publishing, Ltd., 2012.
Original Russian Text © B.R. Kuluev, A.B. Knyazev, Ya.P. Lebedev, A.V. Chemeris, 2012, published in Fiziologiya Rastenii, 2012, Vol. 59, No. 1, pp. 108–117.
The sizes and shapes of plant organs are very
important traits tightly genetically controlled. The
final sizes of plant organs are determined by both sizes
and the numbers of cells. Thus, it is possible to change
an organ size by manipulating cell expansion and divi
sion. The increase in plant cell volume is mainly due to
water uptake by the central vacuole, but because of
rigidity of the cell wall, the expansion is only possible
when cellulose microfibril bonds are soften and bro
ken. Plant tissue extencibility is regulated by acidifying
their cell walls and activation of expression of special
nonenzymatic proteins called expansins. Based on
phylogenetic relationships, the expansins are subdi
vided into four families: (1) expansins A (EXPA) or
expansins, (2) expansins B (EXPB) or
sins, (3) expansinlike proteins A (EXLA), and
(4) expansinlike proteins B (EXLB) . EXPA were
first to be discovered: in 1992 they were isolated from the
cell walls of cucumber hypocotyls . Next year the
homologous proteins crossreacting with antibodies to
cucumber expansins were isolated from oat coleoptiles
. Expansins B were isolated from cereal pollen and
proved to be partially homologous to expansins A .
Each plant species has numerous expansin genes.
The fully sequenced
genome contains 36
expansin genes: 26 EXPA genes, six EXPB genes,
three EXLA genes, and an EXLB gene . Expansins
are small basic proteins 250–270 amino acids long .
Expansins are assumed to participate in breaking non
covalent bonds between cellulose microfibrils and gly
can transverse bridges, thus facilitating cell wall defor
mation . Expression of some isoforms of expansins
was shown to correlate with growth of such structures
as hypocotyls, coleoptiles, internodes, shoots, leaves,
roots, and ripening fruits .
At present expansins are known to not only regu
late cell expansion, but also to be more versatile pro
teins participating in a number of processes of devel
opment and destruction . Thr higher expression of
resulted in shoot
growth retardation especially pronounced at the early
stages of vegetative growth; besides, these transgenic
plants were shown to be more resistant to stress factors
. Overexpression of
significantly affected the growth of transgenic plants.
Of great interest is the
that is actively expressed in petioles and trichomes of
growing leaves and in the basal zones of petioles .
The arabidopsis plants with elevated expression of this
gene were characterized by longer petioles and larger
Morphological and Physiological Characteristics of Transgenic
Tobacco Plants Expressing Expansin Genes:
B. R. Kuluev, A. B. Knyazev, Ya. P. Lebedev, and A. V. Chemeris
Institute of Biochemistry and Genetics, Ufa Research Center, Russian Academy of Sciences,
pr. Oktyabrya 71, Ufa, 450054 Russia;
Received February 17, 2011
—Expansins are nonenzymatic plant proteins breaking hydrogen bonds between cellulose
microfibrils and hemicellulose polymer matrix. Each plant has many expansin genes, whose protein products
participate in the regulation of plant growth and development mainly by regulating cell expansion. To analyze
the effects of elevated expansin expression on the plant organ sizes, we cloned the
. Transgenic tobacco plants expressing the target
genes were obtained. The obtained transgenic tobacco plants were shown to have significantly larger leaves
and longer stems compared to control plants. The flowers were quite insignificantly larger, but at the same
time transgenic plants had more flowers. The microscopic studies showed that the organs of
rying plants were larger mainly due to stimulated cell proliferation, whereas the overexpression of the
gene activated cell expansion.
Keywords: Populus nigra, Nicotiana tabacum, AtEXPA10, PnEXPA1
, CaMV 35S promoter, transgenic plants,
cell expansion, growth regulation, organ sizes.
: BA—benzyladenine; Hyg—hygromycin; MS—
Murashige and Skoog nutrient medium.