The chlorophyll fluorescence (F) temperature curves in a linear time-temperature heating/cooling regime were used to study heat-induced irreversible F changes in primary green leaves of spring barley (Hordeum vulgare L. cv. Akcent). The leaf segments were heated in a stirred water bath at heating rates of 0.0083, 0.0166, 0.0333, and 0.0500 °C s-1 from room temperature up to maximal temperature Tm and then linearly cooled to 35 °C at the same rate. The F intensity was measured by a pulse-modulated technique. The results support the existence of the two critical temperatures of irreversible F changes postulated earlier, at 45-48 and 53-55 °C. The critical temperatures are slightly dependent on the heating rate. Two types of parameters were used to characterize the irreversibility of the F changes: the coefficient of irreversibility μ defined as the ratio of F intensity at 35 °C at the starting/ending parts of the cycle and the slopes of tangents of linear parts of the F temperature curve. The dependence of μ on T m revealed a maximum, which moved from 54 to 61 °C with the increasing heating/cooling rate v from 0.0083 to 0.0500 °C s-1, showing two basic phases of the irreversible changes. The Arrhenius and Eyring approaches were applied to calculate the activation energies of the initial increase in μ. The values varied between 30 and 50 kJ mol-1 and decreased slightly with the increasing heating rate. and J. Frolec ... [et al.].
Net photosynthetic rate (PN) of leaves grown under free-air CO2 enriched condition (FACE, about 200 µmol mol-1 above ambient air) was significantly lower than PN of leaves grown at ambient CO2 concentration (AC) when measured at CO2 concentration of 580 µmol mol-1. This difference was found in rice plants grown at normal nitrogen supply (25 g m-2; NN-plants) but not in plants grown at low nitrogen supply (15 g m-2; LN-plants). Namely, photosynthetic acclimation to FACE was observed in NN-plants but not in LN-plants. Different from the above results measured in a period of continuous sunny days, such photosynthetic acclimation occurred in NN-plants, however, it was also observed in LN-plants when PN was measured before noon of the first sunny day after rain. Hence strong competition for the assimilatory power between nitrogen (N) and carbon (C) assimilations induced by an excessive N supply may lead to the photosynthetic acclimation to FACE in NN-plants. The hypothesis is supported by the following facts: FACE induced significant decrease in both apparent photosynthetic quantum yield (Φc) and ribulose-1,5-bisphosphate (RuBP) content in NN-plants but not in LN-plants. and Z.-H. Yong ... [et al.].
Foliage of Scots pine (Pinus sylvestris L.) and pedunculate oak (Quercus robur L.) was collected in a mixed pine/oak forest at canopy positions differing in radiation environment. In both species, chlorophyll (Chl) a/b ratios were higher in foliage of canopy positions exposed to higher irradiance as compared to more shaded crown layers. Throughout the growing season, pine needles exhibited significantly lower Chl a/b ratios than oak leaves acclimated to a similar photon availability. Hence, pine needles showed shade-type pigment characteristics relative to foliage of oak. At a given radiation environment, pine needles tended to contain more neoxanthin and lutein per unit of Chl than oak leaves. The differences in pigment composition between foliage of pine and oak can be explained by a higher ratio of outer antennae Chl to core complex Chl in needles of P. sylvestris which enhances the efficiency of photon capture under limiting irradiance. The shade-type pigment composition of pine relative to oak foliage could have been due to a reduced mesophyll internal photon exposure of chloroplasts in needles of Scots pine, resulting from their xeromorphic anatomy. Hence, the higher drought tolerance of pine needles could be achieved at the expense of shade tolerance. and U. Hansen, J. Schneiderheinze, B. Rank.
Changes of photosynthesis under blue light were examined in the ABA-overproducing 7B-1 mutant in tomato. Net photosynthetic rate (PN), stomatal conductance (gs), intrinsic water-use efficiency (WUEi) and chlorophyll (a+b) [Chl (a+b)] content in leaves of different insertion (1st, 4th and 9th ones) were measured in 5-, 7- and 9-week-old plants. PN, gs, and Chl (a+b) content were mostly similar in young leaves of 7B-1 and wild type (WT) plants. With the aging of leaves, a blue-light-induced increase in PN and gs to steady-state was delayed and steady-state values of PN and gs were lower in 7B-1 plants compared with WT. Steady-state values of WUEi were increased in 4th and 9th leaves of 7B-1 plants compared with WT. The results can be explained by the higher endogenous level of ABA in 7B-1 plants and their lower sensitivity to ABA in earlier growth stage., E. Ježilová ... [et al.]., and Obsahuje bibliografii
A novel purification procedure was developed for the isolation of oxygen evolving photosystem 2 (PS2) from Mastigocladus laminosus. The isolation procedure involves dodecyl maltoside extraction followed by column chromatography using anion exchange resins. The isolated PS2 reaction center (RC) was analyzed for its biochemical and biophysical characteristics. Analysis by SDS polyacrylamide gel electrophoresis revealed that the complex contained five intrinsic membrane proteins (CP 47, CP 43, D1, D2, and cyt b559) and at least three low molecular mass proteins. The complex exhibited high rates of oxygen evolution [333 mmol(O2) kg-1(Chl) s-1] in the presence of 2.5 mM 2,6-dimethylbenzoquinone (DMBQ) as an artificial electron acceptor. The red chlorophyll a absorption peak of this complex was observed at 673.5±0.2 nm. The isolated PS2 core complex was free of photosystem 1 as inferred from its SDS-PAGE and fluorescence spectrum. The electron transfer properties of the Mastigocladus cells and the purified PS2 core complex were further probed by measuring thermoluminescence signals, which indicated the presence of a primary quinone electron acceptor (QA) in the purified PS2 core complex. and V. M. Ramesh ... [et al.].
a1_Photosystem (PS) II particles retaining a high rate of O2 evolution were isolated from the mesophilic filamentous cyanobacterium, Spirulina platensis. To achieve high production of PSII complexes in the cells, irradiance from halogen incandescent lamps was used. Disruption of cells by vibration of glass beads proved to be the most suitable procedure for isolation of thylakoid membranes. The selectivity of detergents for PSII particle preparation rose in the order of Triton X-100 < decyl-β-D-glucopyranoside < dodecyldimethyl-aminooxide < n-heptyl-β-D-thioglucoside < N-dodecyl-N,N-dimethylammonio-3-propane sulphonate < n-octyl-β-thioglycoside < octylglucoside < n-dodecyl-β-D-maltoside. The last four detergents yielded extracts, from which pure PSII particles not contaminated by PSI complexes could be obtained by sucrose-gradient centrifugation (20-45%) at the 43% sucrose level. We assumed both the acceptor and donor sides of the isolated n-dodecyl-β-D-maltoside (DM) particles to be intact due to high oxygen production by DM particles [1,500 meq(e-) mol-1 (Chl) s-1] achieved in the presence of all artificial acceptors tested. The PSII particle fraction from the sucrose gradient was used with immobilized metal (Cu2+) affinity chromatography (IMAC) for the preparation of the PSII core complex. By washing the column with a MES buffer containing MgCl2 and CaCl2, the phycobiliproteins were stripped off. The PSII core complex was eluted in a buffer containing 1% DM, mannitol, MgCl2, NaCl, CaCl2, and ɛ-aminocaproic acid. SDS-PAGE of the core complex provided pure bands of D1 and D2 proteins and PsbO protein from thylakoid membrane, which were used to raise polyclonal antibodies in rabbits. These antibodies recognized D1 and D2 not only as monomers of 31 and 32 kDa proteins, but also as heterodimers of D1, D2 corresponding to the band of 66 kDa on SDS-PAGE. This was in contrast to antibodies of, a2_synthetic determinants, which reacted only with the monomers of D1 and D2 proteins. These negative reactions against heterodimers of D1, D2 supported the hypothesis that dimeric forms of PSII reaction centre proteins have a C-terminal sequence sterically protected against a reaction with specific antibodies., and E. Šetlíková ... [et al.].
Distinct crystalloids were found in chloroplasts of transgenic Pssu-ipt tobacco (Nicotiana tabacum L. cv. Petit Havana SR1) overproducing endogenous cytokinins. They were present both in rooted (T) and grafted (TC) transgenic plants contrary to control tobacco (C). The fractions enriched by crystalloids were isolated from chloroplasts using a continuous or a discontinuous Percoll gradient. Chlorophyll (Chl) fluorescence emission spectra at 77 K indicated the presence of aggregates of light-harvesting complex proteins (LHC2) that was not connected to reaction centres of photosystem 2 both in isolated chloroplasts and in the fraction of 80 % Percoll gradient from both types of transgenic tobacco. Further analyses, i.e. pigment contents, polypeptide composition by SDS-PAGE, and immunoblotting support our hypothesis that crystalloids inside chloroplasts of transgenic tobacco are formed by LHC2 aggregates. Treatment with two distinct detergents, chosen with respect to their effects (i.e. β-dodecyl maltoside or Triton X-100), resulted in different degree of disintegration of Chl a/b proteins in transgenic plants compared to the control. Electron microscopic observations and immunogold labelling with specific LHC2 antibodies carried on the resin embedded leaf sections or free suspensions of chloroplasts showed that gold particles were bound preferentially on the outer surface of crystalloids. Three-dimensional reconstruction of chloroplasts and crystalloids proved that paracrystalline structures varied moderately in their size and took up a significant portion of total chloroplast volume. and H. Synková ... [et al.].
Prosopis juliflora is a hardy plant tolerant to drought, salinity, extremes of soil pH, and heavy metal stress. We isolated and characterized a photosystem 2 (PS2) gene PsbR (Pj PsbR) and its promoter. Northern analysis for Pj PsbR in P. juliflora leaves under 25 % polyethylene glycol stress showed steady decrease in transcript level at 12, 24, and 48 h after stress application. Under 90 mM H2O2 stress, transcript level dropped drastically at 12 h, but increased again compared to the control at 24 h. A 1.7 kb fragment upstream the 5' UTR of this gene (putative promoter) was isolated and analyzed in silico. Several putative cis-acting DNA elements were identified in this sequence. and G. Suja, A. Parida.
Two different kinds of oxygen evolving photosystem II (PSII) core complexes were isolated in the present study by solubilization of PSII enriched thylakoid membranes from spinach with the non-ionic detergent 6-O-(N-heptylcarbamoyl)-methyl-α-D-glucopyranoside (Hecameg) under different conditions. The PSII core complex isolated at higher ionic strength was similar to that isolated by using octyl-β-D-glucopyranoside (OGP) and lacked the 23 and 17 kDa extrinsic proteins of the oxygen evolving complex but retained the 22 kDa PsbS protein. Solubilization of the PSII membranes with Hecameg at lower ionic strength allowed the isolation of another PSII complex that retained all the three extrinsic proteins (33, 23 and 17 kDa) of the oxygen evolving complex but was depleted of the 22 kDa PsbS protein. This complex exhibited high rates of oxygen evolution and was found to be more sensitive to DCMU indicating a better structural and functional integrity and may be treated as the minimal functional unit required for PSII photochemistry. The detergent Hecameg is relatively inexpensive and the methodology remains simple since it does not require any chromatography or density gradient ultracentrifugation.
Early light-induced proteins (ELIPs) are nuclear-encoded thylakoid proteins. In the present research, two full-length cDNAs (741 and 815 bp), encoding ELIPs (190 and 175 aa) and their genomic sequences, were isolated from tea leaves, and named CsELIP1 and CsELIP2, respectively. Both the deduced CsELIPs contain a chloroplast transit peptide in the N-terminus and a chlorophyll a/b binding protein motif with three transmembrane helices in the C-terminus. The genomic sequences of the two CsELIPs conform to the three-exon pattern of ELIP genomic sequences of other plant species. However, the identities between two CsELIPs and ACJ09655 from gymnosperm species were higher than all of
ELIP-like proteins identified from other angiosperms. Expression analysis showed that the two CsELIP genes were significantly
up-regulated when the photoinhibition occurred in tea leaves, implying that they might be involved in photoprotection., X. W. Li ... [et al.]., and Obsahuje bibliografii