ISSN 1021-4437, Russian Journal of Plant Physiology, 2006, Vol. 53, No. 2, pp. 278–286. © MAIK “Nauka /Interperiodica” (Russia), 2006.
Original Russian Text © G.A. Romanov, S.S. Medvedev, 2006, published in Fiziologiya Rastenii, 2006, Vol. 53, No. 2, pp. 309–319.
In the Czech Republic, a leading center has emerged
long ago for plant hormone studies, primarily those of
cytokinins and auxins. It is therefore quite natural that
the Czech Republic has hosted the most representative
meetings on phytohormones. The recent International
Symposium “Auxins and Cytokinins in Plant Develop-
ment” was held in Prague on July 7–12, 2005 as a fol-
low up to the previous meeting in 1999. It is noteworthy
that the discovery of phytohormone receptors (the cyto-
kinin receptors in 2001 and quite recently, those for
auxin) and of the molecular mechanisms of their activ-
ities greatly enhanced the general interest to auxins and
cytokinins. Hence, it is not surprising that over 200 sci-
entists from about 30 countries, including far-off Aus-
tralia, Saudi Arabia, and South Africa, participated in
the Symposium. The party from the neighboring Ger-
many (22 scientists) was second to that of the hosts, fol-
lowed by the delegations from the United States
(15 participants), Great Britain (10), South Korea (10),
France (9), Israel (8), and Japan (7). This time Russia
was properly represented by six scientists, exceeding
Italy, Sweden, Denmark, The Netherlands, and Spain in
the number of participants. Among 60 oral presenta-
tions, three were made by the Russian scientists. In
addition, there were posters presenting joint research
by the Russian, Czech, and Ukrainian participants
, and Kravets
As usually, it is our pleasure to mention the excellent
organization of the Symposium: due to the efforts by
E. Za ímalová, R. Va ková, M. Kamínek, I. Machá k-
ová, and other hosts from the Institute of Experimental
Botany, Academy of Sciences, Prague, the heavily
packed schedule of the meeting nevertheless left
enough time to participants for informal discussion and
development of new joint projects.
The program of the Symposium comprised such
issues as phytohormone biosynthesis and metabolism,
transport, signaling, pattern formation and develop-
ment, auxin–cytokinin crosstalk, responses to environ-
ment, and novel methods.
The major model plant,
been employed in approximately half of the presented
works. As a whole, the oral and poster communications
demonstrated remarkable advance in elucidating the
molecular mechanisms of auxin and cytokinin activi-
ties and the particular pathways involved in the phyto-
hormone regulation of plant growth and development.
Due to the limited space, this review deals only with
selected aspects of the scientiﬁc program: we had to
concentrate on the most essential and intriguing data
presented at the Symposium.
MOLECULAR ASPECTS OF HORMONE ACTION
Auxin is the most important or at least one of the
most important hormones of higher plants. It activates
cell division and expansion, is essential for the develop-
ment of vascular tissues and lateral roots, produces a
sink capacity, and is the major factor of tropisms and
nasties. The polar IAA transport determines the phe-
nomenon of apical dominance and spatial patterning
and tissue differentiation in the course of plant morpho-
genesis and development. Dozens of genes have been
characterized with their expression up-regulated or
down-regulated by IAA. These genes include the early
genes and the genes of secondary response (late genes).
Promoters of the early genes contain the conserved
DNA regions that determine the response to IAA; these
regions are called auxin response elements (
What is the mechanism for auxin signal perception
and in what way the signal reaches the target genes in
the plant cell?
The initial candidate for the role of auxin receptor
was a 22-kD polypeptide that forms a homodimer and
is localized at the endoplasmic reticulum (Napier
Plant Mol Biol.
, 2002, vol. 49, pp. 339–348). This pro-
tein was named auxin-binding protein 1 (ABP1). In
maize, ﬁve genes encode ABP1 proteins, and only one
By its structure, ABP1 is a hydro-
philic glycoprotein with a signal sequence at its C-ter-
minus (KDEL) characteristic of the endoplasmic-retic-
ulum protein (see
Russ. J. Plant Physiol.
, 2002, vol. 49,
pp. 552–560 for a detailed description of ABP1). How-
ever, no real link between ABP1 and auxin-dependent
gene activation was shown. Only recently, when
another major auxin receptor was identiﬁed, the whole
Auxins and Cytokinins in Plant Development.
Advances in Phytohormone Studies.
The Second International Symposium
(Prague, Czech Republic, July 7–12, 2005)