ACTA BIOLOGICA CRACOVIENSIA

PHOTOSYNTHESIS, PHOTOCHEMISTRY, AND PHOTOPROTECTION BY CAROTENOIDS
ORAL PRESENTATIONS
Photoprotection by carotenoids of Plantago
media photosynthetic apparatus in natural
conditions
Tamara Golovko, Olga Dymova, Ilya Zakhozhiy, Igor Dalke,
Galina Tabalenkova
Institute of Biology, Komi Science Centre, Ural Branch of Russian
Academy of Sciences, ul Kommunisticheskaya, 167982,
Syktyvkar, Russia, golovko@ib.komisc.ru
Carotenoids, apart of their antenna function in photosynthesis,
play an important role in protection of photosynthetic apparatus.
Role of protection mechanisms increases with enhancement of
climate instability and under environmental stresses. Daily pattern
of photosynthesis and carotenoids were studied in the sun
and shade plantain plants in the field (62°45 N, 55°49 E) in July
2007-2011 (Golovko et al., 2011). The sun plants growing on the
open site differed from shade plants growing in dense herbage in
terms of CO 2 exchange rate and photosynthetic pigments content.
HPLC-analysis revealed the presence of β-carotene (β-Car) and
xanthophylls in carotenods pool. The total pool of xanthophylls
[violaxanthin (V) + antheraxanthin (A) + zeaxanthin (Z)] and the
conversion state (Z+0.5A)/(V+A+Z) increased from morning to
midday in sun plants. The percentage of V in VAZ pool was the
greatest (85-90%) at midnight and decreased to 10% at noon. An
increase in Z content occurred concomitantly with the V
decrease. Maximum part of Z in VAZ pool was 60%. The conversion
state of violaxanthin cycle pigments (VCP) was significantly
lower in shade plants than in sun plants, especially in the morning.
With using of epoxidase inhibitor we showed that V which
was not involved in conversion was about 20% of total V pool. The
photosynthesis of sun leaves was depressed strongly at midday,
but changes of maximum quantum yield of PS2 (Fv/Fm) were not
apparent at that time. The highest qP (photochemical quenching)
was found at early morning and afternoon. qN (non-photochemical
quenching) in the sun leaves increased sharply at midday. The
direct relation between heat dissipating and the conversion state
of VCP in plantain leaves was revealed. Apart from VCP, other
carotenoids (lutein, neoxanthin, and β-carotene) can also take
part in protection of PA. The results presented here clearly
demonstrate that the plantain leaves resistance to excess solar
radiation is determined by activation of qN mechanisms associated
with the VCP de-epoxidation.
REFERENCE
GOLOVKO TK, DALKE IV, ZAKHOZHIY IG, DYMOVA OV, TABALENKOVA GN.
2011. Functional plasticity of photosynthetic apparatus and its
resistance to photoinhibition in Plantago media. Russian
Journal of Plant Physiology 58: 549-559.
Orange Carotenoid Protein related
photoprotective mechanism in cyanobacteria
Michal Gwizdala, Adjele Wilson, Diana Kirilovsky
DSV/iBiTec-S/SB2SM, CEA Saclay, 91191 Gif-sur-Yvette, France,
michal.gwizdala@cea.fr, adjele.wilson@cea.fr,
diana.kirilovsky@cea.fr
Photosynthetic organisms have developed mechanisms protecting
themselves from high light by thermal dissipation of excess
absorbed energy. In cyanobacteria the photoactivation of the
Orange Carotenoid Protein (OCP) is required for triggering one of
such photoprotective mechanisms. The OCP is a soluble 35 kDa
Vol. 53, suppl. 1, 2011
17–22 July 2011, Krakow, Poland
protein carrying a ketocarotenoid, the 3'-hydroxyechinenone
(hECN) and composed of two domains: an all -helical N-terminal
domain and an α/β C-terminal domain. The inactive orange form
of OCP under high light illumination undergoes structural
changes in the carotenoid and in the protein leading to the formation
of the red active form of OCP. The active red form induces
an increase of thermal dissipation of the energy absorbed by the
phycobilisome, the cyanobacterial extra-membrane antenna of
the photosystem II. This diminishes the effective size of the antenna,
decreasing the energy arriving to the reaction center and it is
accompanied by a decrease of phycobilisome fluorescence. We
have identified a novel protein that mediates the recovery of the
full antenna capacity when irradiance decreases: the
Fluorescence Recovery Protein (FRP). In Synechocystis PCC
6803, this protein is encoded by the slr1964 gene, downstream
the OCP encoding gene. Homologous of the slr1964 gene are present
in all the OCP – containing strains. The FRP is a 13 kDa protein
that interacts with the active red form of the OCP and accelerates
its conversion into the orange inactive form. Recently we
have reconstituted the photoprotective mechanism in vitro using
isolated phycobilisomes, OCP and FRP in order to further understand
the interaction of these three elements. This characterization
is a new essential approach in the understanding of the OCPrelated
photoprotective mechanism in cyanobacteria.
Electric field-induced Fano effect in UV
absorption spectra of carotenoids
Stanisław Krawczyk, Rafał Luchowski
Institute of Physics, Maria Curie-Skłodowska University,
Pl. M. Curie-Skłodowskiej 1, 20-031 Lublin, Poland,
skraw@hektor.umcs.lublin.pl
The order and symmetry properties of electronic excited states of
carotenoids are still a matter of debate, especially concerning the
UV-excited states higher in energy than the 1 1 B u state attainable
by excitation with visible light. A general difficulty is associated
with the occurence of "dark" states of A g symmetry, which are not
observed in absorption spectra. In principle, the perturbation of
the electronic states should cause a state mixing which can be
observed as an electric field-induced light absorption. Apparently
no such effect was observed in electronic transitions in
carotenoids examined with the Stark effect (i.e. electroabsorption)
spectroscopy in the spectral range covering the lowest 2 1 A g
and 1 1 B u states, and in the higher energy "cis" band of carotenoid
isomers (Krawczyk et al., 2006). However, we have observed significant
and characteristic electric field-induced change in
absorption, covering the next UV band resulting from a g-u transition.
The electroabsorption signal consists of a dispersion-like,
wide and apparently structureless biphasic band which adds to
the typical derivative-like shape characteristic for carotenoids.
This effect was observed in three carotenoids examined –
lycopene, violaxanthin and zeta-carotene, and some of their isomers.
The shape of this additional signal suggests an electric
field-induced mixing of the discrete-energy excited state with the
continuum of vibronic states of some lower-energy electronic
state, and seems to be the case of the Fano effect (Fano 1961),
well known in the exciton spectra of solids. This effect depends
on the symmetry of electronic states involved which are mixed by
the electric field. It seems that the analysis of this effect by its
quantitative modeling based on vibronic coupling theory in linear
polyenes can supply good premise for the complete classification
and symmetry assignment to the higher excited states of
carotenoids, and indirectly also to lower states, and to explain the
apparent lack of such effects in lower-energy spectra of
carotenoids.
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