ISSN 10214437, Russian Journal of Plant Physiology, 2015, Vol. 62, No. 2, pp. 219–223. © Pleiades Publishing, Ltd., 2015.
The enhanced UVB radiation recorded during the
last decades is recognized as an inevitable conse
quence of stratospheric ozone depletion resulting
from the badly regulated industrial activity, while
exerting a deleterious effect on both animal and plant
organisms . The direct damage of biologically
important molecules by highly energetic UVB pho
tons is supplemented by the UVBinduced rise in
reactive oxygen species (ROS) accomplishing dual
functions – from oxidative injury to signaling and pro
tection [2, 3]. Hydrogen peroxide (
), a central
metabolite in the ROS network, is a key player in the
signal transducing pathways of plants, known to
induce transcriptional reprogramming leading to the
expression of defense responses, including pro
grammed cell death (PCD) [4, 5].
Research on the induction of ROS by UVB rays, as
well as on the further metabolic implications of ROS is
predominantly carried out on higher plants [3, 4, 6, 7].
Few data are reported for cyanobacteria  and mac
roalgae , while the information about green
microalgae is also scarce [10–13]. Noticeably, in the
above organisms UVinduced components of ROS
pool have been determined by a relatively lowspecific
electron paramagnetic resonance (EPR) or fluorimet
ric techniques, but no specific detection of
been performed. In a previous paper  by using a
specific chemical test for
, we established a bipha
This text was submitted by the authors in English.
sic burst of
in UVBexposed green microalga
originating from the Antarctic zone.
To the best of our knowledge, it was the first report on
the biphasic oxidative burst in plants induced by
UVB rays. These data, together with cell viability
characteristics of the alga, allowed us to suggest the
occurrence of a PCDlike response to UVB stress.
The aim of the present work is to follow the fluctu
ations in the content of
and total hydroperoxides
as well as the cell viability in cell suspension cultures of
habitats contrasting to the Antarctic ones, such as
those of temperate climate. Thus, the abovedescribed
mechanisms employed by
UVB stress could be defined as genotype or environ
MATERIALS AND METHODS
Microalgal organism and growth conditions.
was obtained from the Culture Collection
of Autotrophic Organisms (CCALA) at the Institute of
Botany, Academy of Sciences of the Czech Republic.
The alga was cultivated intensively for 5 days before
being subjected to UVB radiation. The nutrient
medium of Georgiev et al.  was used. The cell sus
pensions were grown aseptically in 200mL glass ves
sels at 28°C under continuous white light illumination
s) photon flux density and aeration of
h) with 2%
UVB treatment and sampling.
grown cultures with cell density of 1.5 mg dry mat
ter/mL were placed in open Petri dishes as a 3mm
deep layer. Cells were exposed to UVB radiation for
15, 30, 60, and 240 min. As a source of UVB radiation
UVB Radiation Induces Biphasic Burst of Hydrogen Peroxide
A. M. Edreva, I. D. Pouneva, and E. Zh. Gesheva
Institute of Plant Physiology and Genetics, Bulgarian Academy of Sciences, ul. Acad. G. Bonchev 21, 1113 Sofia, Bulgaria;
fax: (359 2) 873 9952; email: email@example.com
Received May 15, 2014
—The fluctuations of hydrogen peroxide and total hydroperoxides were followed up at different time
points in UVBirradiated cell suspension cultures of the green microalga
A biphasic burst
of hydrogen peroxide was recorded, while cell viability was strongly reduced. This pattern is similar to the two
wave oxidative burst in plants expressing hypersensitive response to pathogens and PCD and implies the
occurrence of a PCDlike response in UVBexposed unicellular green algae.
Keywords: Chlorella vulgaris
, UVB, reactive oxygen species
: EPR—electron paramagnetic resonance;
PAR—4(2pyridylazo)resorcinol; PCD—programmed cell
death; TCA—trichloroacetic acid; TTC—triphenyl tetrazo