ACTA BIOLOGICA CRACOVIENSIA

PHOTOSYNTHESIS, PHOTOCHEMISTRY, AND PHOTOPROTECTION BY CAROTENOIDS
2.8.
COP1 regulates biosynthesis and degradation
of xanthophylls in Arabidopsis seedlings
Pawel Jedynak1 , Tomasz Panz2 , Beata Myśliwa-Kurdziel1 ,
Andrzej Waloszek1 , Kazimierz Strzałka1 , Przemysław Malec1 1 2 Department of Plant Physiology and Biochemistry, Department
of Biophysics, Faculty of Biochemistry, Biophysics and
Biotechnology, Jagiellonian University, Gronostajowa 7,
30-387 Krakow, Poland, pawel.jedynak@uj.edu.pl,
tomasz.panz@uj.edu.pl, b.mysliwa-kurdziel@uj.edu.pl,
andrzej.waloszek@uj.edu.pl, kazimierz.strzalka@uj.edu.pl,
przemyslaw.malec@uj.edu.pl
COP1 (constitutive photomorphogenesis 1) is an E3 ubiquitin-protein
ligase involved in signaling pathways mediating gene expression
in both plant and animal cells. In plants, COP1 is crucial in
the developmental switch to autotrophy during the first exposure of
emerging seedlings to light (deetiolation). During deetiolation, the
light-triggered photoreduction of protochlorophyllide (Pchlide) to
chlorophyllide (Chlide), catalyzed by light-dependent protochlorophyllide
oxidoreductase (LPOR), has a key role in the regulation of
Chl biosynthesis. Carotenoids are photoprotective and antioxidant
pigments synthesized in plants. In particular, xanthophylls were
found to be essential for the formation of the prollamellar body
(PLB) [1]. Violaxanthin was demonstrated to be bound in photoactive
complexes of NADPH:LPOR [2]. In this study, using Reversed
Phase-HPLC and fluorescence spectroscopy, we estimated pigment
composition in 5 days old etiolated seedlings of cop1 mutant, previously
shown to accumulate high amounts of Pchlide not complexed
in PLB's. In darkness and under moderate light conditions
(100 μE m -2 s -1 ) the concentrations of lutein and violaxanthin in
cop1 seedlings were 2-3 times higher in comparison to wild type
(WT). In contrast, the irradiation with an excessive light intensity
(400 μE m -2 s -1 ), resulted in the decrease of violaxanthin concentration
in cop1 mutant, whereas lutein concentration was not altered
under that conditions. Preferential degradation of violaxanthin was
neither accompanied with the formation of antheraxanthin/zeaxanthin
nor observed in WT seedlings. This effect correlated with a
rapid photodegradation of Pchlide observed in cop1 seedlings in
strong light. Our results indicate that COP1 is a negative regulator
of xanthophyll biosynthesis in darkness. Additionally, under light
conditions, COP1 may regulate processes that maintain physiological
levels of photoprotectants and/or anitioxidants during seedling
deetiolation.
REFERENCES
PARK H et al. 2002. The Plant Cell 14: 321-332.
CHACHDI M et al. 1998. Planta 206: 673-680.
2.9.
Electrochromism of carotenoid photosensitizers
adsorbed on TiO2 Agata Zdyb1 , Stanisław Krawczyk2 1 Faculty of Environmental Engineering, Lublin University of
Technology, ul. Nadbystrzycka 40B, 20-618 Lublin, Poland,
a.zdyb@pollub.pl
2 Institute of Physics, Maria Curie-Skłodowska University,
Pl. M. Curie-Skłodowskiej 1, 20-031 Lublin, Poland,
skraw@hektor.umcs.lublin.pl
The development of new organic sensitizers for the purposes of
dye sensitized solar cells and photocatalysis requires a better
understanding of the complexity of their electronic states on the
Vol. 53, suppl. 1, 2011
surface of TiO 2 – the oxide semiconductor widely used in research
and prototype constructions. This communication presents a study
of carboxylated derivatives of all-trans carotenoids retinoic acid
(RA) and bixin by Stark effect (electroabsorption) spectroscopy in
glassy ethanol at low temperature. They were studied both as free
monomeric species and when adsorbed to nanoparticles of titanium
dioxide in the presence of variable concentration of acetic acid.
Both pigments adsorbed completely at the lowest acid contents
(