Proceedings
Proceedings of Fourth International Symposium on Plant Signaling and Behavior
4th International Symposium
19–24 June 2016
19–24 June 2016
St. Petersburg, RUSSIA
Complex Adaptive and Neuron-Like Reactions
Location of signaling molecules in common regulatory system of cells,
organs, organisms
Chikov V.I.
Kazan Institute of Biochemistry and Biophysics, Kazan Research Center, Russian Academy of
Sciences, ul. Lobachevskogo 2/31, P.O. B 30, Kazan, Tatarstan, 420111 Russia
[email protected]
The report presents and gives scientific credence to the conception of a trigger mechanism engaging
signaling molecules into metabolic regulation and based on selectively changed direction or intensity of
a substance flow in stationary biochemical reactions in cells, organs or systems. The core principles of
the conception are as follows.
1. Any biological system is an open system. All the internal changes are caused by the changing external
existence conditions.
2. Most of trigger mechanisms for regulatory process in a cell, organ or system are performed at the
epigenomic level, and the variety of choices for the regulation is vastly enormous.
3. Metabolic disturbance which happens in one cell may launch a chain reaction through the changes in
metabolic flows and lead to imbalance in other organs and tissues which are relevant to the changes in
particular mass metabolic flow; signaling molecules are involved in the process as well. Thus, signaling
molecules are enabled by changing the mass transport of a substance caused by some internal or external
factor. Internal factor in this context is considered to be ontogenetic DNA-reading.
4. The regulatory mechanisms of general biological coordination in cells, tissues and organs often
depend on different levels of gene expression, forming quick responses.
5. The respective signaling molecules are in charge of certain places and some biochemical reactions in
order to start or quit the processes, but the very signaling molecules are produced because of some
changes induced by certain factors.
The data to support this conception are presented.
Nanoparticles induce signalling reactions and affect physiological processes
in Arabidopsis thaliana plants
Demidchik V.1,2; Sosan A.3, Svistunenko D.3, Przhevalskaya D.1, Leshchanka Y.1, Straltsova D.3,
Smolich I.1, Lawson T.3, Subramaniam S.3, Golovko V.4, Anderson D.4, Colbeck I.1, Sokolik A.1
1
Belarusian State University, Minsk, Belarus
Komarov Botanical Institute RAS, Saint Petersburg, Russia
3
University of Essex, Colchester, UK
4
University of Canterbury, Christchurch, New Zealand
[email protected]
2
Nanoparticles (NPs) have gained particular attention from industrialists due to their relatively low cost
of production and tremendously enhanced physical/chemical characteristics. Silver nanoparticles (Ag
NPs) are the world's most important nanomaterial. Nearly 25% of all nanotechnology consumer
products include Ag NPs. The dramatic increase in industrial use of Ag NPs has raised considerable
concern about their potential release and effects on flora and ecosystems, as well as the possibility of it
entering human food chain through plants. The soil concentration of Ag NPs in agricultural land
(estimates for USA, 2012) exponentially increases, mainly due to the treatment with Ag-NP-polluted
sludge, with the average predicted concentration of Ag NPs in the soil of approximately 8 mg kg-1
(Gottschalk et al., 2013, Environ Pollut). This is an average number while “hotspots” contain much more
nanosilver. Concentrations of Ag NPs in surface water and sewage treatment have been increasing
significantly in recent years.
In this work, we have aimed to establish the pattern of regulatory and stress reactions of manufactured
Ag NPs in model plant Arabidopsis thaliana, at the organismal level (root and leaf growth) and at the
cellular level (Ca2+ signalling, ROS generation, plasma membrane conductances, photosynthetic
efficiency). We also examined the Ag accumulation in higher plants cultivated on Ag NP-containing
media, and the potential action of Ag NPs on extracellular L-ascorbic acid.
We have shown that addition of Ag NPs to cultivation medium, at levels above 300 mg L-1, inhibited
Arabidopsis thaliana root elongation and leaf expansion. This also resulted in decreased photosynthetic
efficiency and extreme accumulation of Ag in tissues. Acute application of Ag NPs induced transient
elevation of [Ca2+]cyt, and accumulation of ROS. Whole-cell patch-clamp measurements on root cell
protoplasts demonstrated that Ag NPs slightly inhibited plasma membrane K+ efflux and Ca2+ influx
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currents or caused membrane breakdown. However, in excised outside-out patches, Ag NPs activated
Gd3+-sensitive Ca2+ influx channels with unitary conductance of approximately 56 pS. Bulk particles did
not modify the plasma membrane currents. Tests with electron paramagnetic resonance spectroscopy
showed that Ag NPs were not able to catalyse hydroxyl radical generation but they directly oxidised the
major plant antioxidant, L-ascorbic acid.
Overall, the presented data sheds the light on mechanisms of the impact of nanosilver on plant cells and
show that these include induction of classical stress signalling reactions (mediated by [Ca2+]cyt and ROS)
and a specific effect on the plasma membrane conductance and the reduced ascorbate.
This study was supported by Russian Science Foundation grant #15-14-30008 to VD.
Regulation of plant fiber development: RNA-seq snapshot of transcription
factors
Gorshkov O.V., Mokshina N.E., Gorshkova T.A.
Institute of Biochemistry and Biophysics, Kazan, Lobachevsky str., 2/31, 420111, Russia
[email protected]
Higher plant organism consists of around 40 functionally different cell types. Their specialization is
among the major processes of plant ontogenesis. The study of a plant cell functional specialization is
usually hampered by the difficulty or even impossibility to isolate plant cells of certain type and at certain
stage of development in the quantities sufficient for in-depth characterization. Since plant samples
usually contain many different cell types, it is difficult to characterize tissue (cell)-specific processes. One
of the rare experimental systems that permit(s) to study specialization of certain cell type in planta is
developing primary phloem fibers of flax (Linum usitatissimum L.). The major function of mature flax
phloem fibers is the provision of strength and flexibility to high and narrow stem, which experiences
severe mechanical stresses.
Plant fibers are the most widely spread type of cells in mechanical tissues in the vegetative organs of the
terrestrial vascular plants. Two key processes have the major impact on the specialization of the plant
fibers: intrusive growth and the cell wall thickening. These two stages are distinctly separated in time
and space, allowing to analyze tissue and stage-specific components. At advanced stage of specialization
the fibers of many plant species form a special type of the cell wall - fiber-specific cellulose-enriched cell
wall type, or a tertiary cell wall (TCW). Unlike the secondary cell wall (SCW), that consists of cellulose,
hemicelluloses and lignin, TCW is rich in cellulose (up to 90%) and lacks detectable xylan and lignin.
The synthesis of TCW always begins after deposition of at least one layer of SCW. The molecular events
associated with the activation and regulation of gene expression during two key stages - the elongation
growth and the tertiary cell wall synthesis - have not been studied at all yet.
We performed large-scale transcriptional profiling of the fibers, taken at different development stages.
Due to the compact (within bundles) location in stem and presence of thick cell wall, phloem fibers at
advanced stage of specialization can be effectively purified from the surrounding tissues and used for
various types of analysis. After sequencing using the platform Illumina, about 95% of single-end reads
(75bp) were successful mapped to the reference sequence using the Cufflinks protocol. In total,
expression of 36012 genes was detected across all samples, while whole-genome assembly of flax
contains 43484 protein-coding genes (Wang et al., 2012). Results of analysis using the algorithm
CuffDiff have indicated that 1124 genes had statistically significant differences in expression level at
values of q<0,05 at least in one pair of the analyzed samples.
Out of 2481 genes of transcription factors indentified in flax genome and classified into 57 families (Jin
et al., 2014), 2027 were detected in our experiment. Transcriptome profiling revealed that the expression
of secondary wall NAC (NST1, SND1) and MYB (MYB46, 83, 20, 52, 63, 103 and others) transcription
factors activating and regulating the SCW formation (Zhong et al., 2010; Hussey et al., 2013; Didi et al.,
2015) is absent or greatly reduced in fibers at advanced stage of specialization compared with other
tissues or fibers at stage of intrusive growth. Also we detected considerably lowered level of transcript
abundance in fibers with tertiary cell wall for all known genes that are ascribed to xylan synthesis and
for most of those involved in phenylpropanoid metabolism leading to lignin formation. At the same
time in fibers, the most abundantly expressed genes coding bZIP, CO-like, HD-ZIP, MYB-related, NAC
and TCP families. This indicated that the initiation and control of TCW synthesis are likely associated
with the activation of other transcription factors, candidates for which are identified in our study.
This work was supported by RSF (#16-14-10256).
Jin JP. et al. (2014) Nucl. Acids Res. 42(D1), D1182-D1187
Wang ZW. et al. (2012) Plant J. 72, 461-473
Zhong R. et al. (2010) Trends Plant Sci., 2010. 15(11):625-32
Hussey SG. et al. (2013) Front. Plant Sci., http://dx.doi.org/10.3389/fpls.2013.00325
Didi V. et al. (2015) J. Exp.Bot., doi: 10.1093/jxb/erv222
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