1021-4437/01/4803- $25.00 © 2001
Russian Journal of Plant Physiology, Vol. 48, No. 3, 2001, pp. 333–339. Translated from Fiziologiya Rastenii, Vol. 48, No. 3, 2001, pp. 392–399.
Original Russian Text Copyright © 2001 by Kochubei.
Since the 1970s, after the discovery of spatial sepa-
ration of PSI and PSII complexes located in intergranal
and granal thylakoids and its substantiation, the present
view of the speciﬁcity of these regions of the chloro-
plast membrane system became generally accepted.
This view was repeatedly conﬁrmed by characterizing
the fragments of respective thylakoids.
It was widely accepted that granal and intergranal
thylakoids represent two special chloroplast regions.
However, in the very late 1980s, it was suggested that
there exists a third speciﬁc region, namely, the marginal
regions of granal thylakoids . They are located in the
curved thylakoid regions, are free from stacking with
neighboring thylakoids, and are stroma-exposed. These
regions of granal thylakoids were named “margins of
chloroplast grana”. In Albertsson’s laboratory, the frag-
ments corresponding to the marginal regions of spinach
thylakoids were isolated and their properties were
investigated [2–5]. To this end, mechanical thylakoid
fragmentation, two-phase partition of fragments, and
their differential centrifugation were used .
The marginal region is characterized by the pres-
ence of a speciﬁc PSI differing in its properties from
that located in the intergranal thylakoids. This PSI
interacts with a speciﬁc pool of LHCII ; it has a
larger light-harvesting antenna  and is characterized
by speciﬁc features of photochemical reactions . In
margin fragments, the size of the light-harvesting
antenna of PSII was smaller . We showed that, after
fragmentation of pea and maize thylakoids with digito-
nin, one of the light fractions sedimenting at 70000
contained particles differing in their properties from the
intergranal thylakoid fragments [6, 7]. A larger size of
these particles  was comparable to that suggested for
the margin fragments of spinach granal thylakoids ;
the presence of a coupling factor at their surface 
indicated that they originated from the stroma-exposed
thylakoid regions. However, in this fraction, the margin
fragments were mixed with fragments of intergranal
thylakoids. Therefore, the goal of this work was to iso-
late a purer fraction of these particles and to investigate
their properties in more detail.
Organization of the Marginal Regions of Pea Granal Thylakoids
S. M. Kochubei
Institute of Plant Physiology and Genetics, National Academy of Sciences of Ukraine,
Vasil’kovskaya ul. 31/17, Kiev, 03022 Ukraine;
fax: (10 380 44) 25-3515; e-mail: skbioﬁs@naverex.kiev.ua
Received March 28, 2000
—Thylakoids of pea chloroplasts isolated from plants grown during various time intervals from June
to August were subjected to fragmentation. Using a modiﬁed procedure, a fraction of larger particles was sep-
arated from those previously considered as fragments of intergranal thylakoids. The particles of the fraction iso-
lated were identiﬁed as fragments of marginal regions of granal thylakoids (margins). The relative yield of these
fragments depended on the time interval of plant growth. Two types of low-temperature ﬂuorescence spectra
corresponding to a high and low yield of the fraction were detected. The characteristics of the ﬁrst one were a
high ﬂuorescence intensity in the short-wave region and the presence of bands with maxima at 687 and 696 nm
emitted by photosystem II (PSII). The ratio of PSII to PSI complexes (PSII/PSI) in the fractions characterized
by a low and high yield varied from 1 to 5. The analysis of excitation spectra of long-wave ﬂuorescence of PSI
showed that PSI complexes in the margin fragments obtained at a low fraction yield were depleted in chloro-
phyll forms with a 682-nm absorption maximum and enriched in those with a 668-nm maximum. Since an
increase in the yield of the margin-fragment fraction is due to an increased unstacking of granal thylakoids, the
differences in the characteristics of fragments obtained with a low and a high yield reﬂect the changes in the
composition of granal thylakoids in the direction from the margin to the centrum, that is, a decrease in the rel-
ative content of PSI complexes and alterations in the composition and size of its light-harvesting antenna. The
consistency between the data obtained and the present view concerning the different functions of PSI located
in different thylakoid regions is discussed.
Key words: Pisum sativum - thylakoids - grana margins - photosystem I - low-temperature ﬂuorescence - ﬂuo-
rescence excitation spectra
LHCI and LHCII—light-harvesting chlorophyll
plexes of I and II; P700—pigment of the photosystems I reaction
center; PSI and PSII—photosystems I and II.