NYB is chlorophyll-less barley mutant, which is controlled by a recessive nuclear gene. The mutation mechanism is revealed. The activities of enzymes transforming 5-aminolevulinic acid into protochlorophyllide were the same in both NYB and the wild type (WT), but the activity of the protochlorophyllide oxidoreductase (POR) in WT was much higher than that of NYB. Most of the photosystem 2 apoproteins were present in both WT and NYB, suggesting that the capability of protein synthesis was probably fully preserved in the mutant. Thus chlorophyll (Chl) biosynthesis in NYB was hampered at conversion form protochlorophyllide (Pchlide) into chlorophyllide. The open reading frame of porB gene in NYB was inserted with a 95 bp fragment, which included a stop codon. The NYB mutant is a very useful material for studies of Chl biosynthesis, chloroplast signalling, and structure of light-harvesting POR-Pchlide complex (LHPP). and Z.-L. Liu ... [et al.].
The last step for biosynthesis of c type cytochromes, indispensable for photosynthesis in cyanobacteria and plants, involves heme transport across the membrane and its covalent attachment to the apoprotein. In cyanobacteria, heme attachment occurs in the thylakoid lumen and probably also in the periplasm and requires at least four proteins, believed to be organized in intrinsic membrane protein complex. To allow isolation and identification of such complex, CcsB protein was tagged with 6xHis tag on its N terminus and expressed under the strong psbAII promoter in the cyanobacterium Synechocystis sp. PCC 6803. Similarly, CcsA protein was tagged with FLAG tag under the control of the same promoter. Although expression of both proteins under strong cyanobacterial promoter did not increase steady state contents of the CcsB protein, the fusion tags did not influence properties of the CcsB and CcsA proteins and the resulting mutants had the same phenotype as the wild type. Protein fraction containing CcsBHis protein was partially isolated from the solubilised membranes under native conditions.
Natural and commercial Salix clones differ in their ecophysiological response to Zn stress This study was carried out to determine the effect of different zinc concentrations on the ecophysiological response of Salix clones: four commercial clones (“1962”, “1968”, “Drago”, and “Levante”) selected for short rotation coppice, and one natural clone, “Sacco”, obtained from a contaminated area. Gas exchanges, chlorophyll a fluorescence (JIP-test), relative chlorophyll content, and biometric parameters were measured in plants grown for fifteen days in soil containing Zn concentrations of 0, 300, 750, and 1,500 mg(ZnCl2) kg-1. Ecophysiological response to metal stress differed in dependence on the Zn concentration and clone. At the low Zn concentration (300 mg kg-1), the absence of any significant reductions in parameters investigated indicated an efficient plant homeostasis to maintain the metal content within phytotoxic limits. Stomatal limitation, observed at 750 and 1,500 mg kg-1, which was found in all clones after three days of the treatment, might be caused by indirect effects of metal on guard cells. Among commercial clones, “Drago” was more sensitive to Zn stress, showing inhibition of growth, while “1962” clone showed a downregulation of PSII photochemistry following the slowdown in the Calvin-Benson cycle. On the contrary, the natural Salix clone (“Sacco”) performed better compared to the other clones due to activation of a photosynthetic compensatory mechanism., A. Bernardini, E. Salvatori, S. Di Re, L. Fusaro, G. Nervo, F. Manes., and Obsahuje seznam literatury
Natural occurrence of C4 species, life form, altitude pattern, and infection by the Three Gorges Project (TGP) were studied in the TGP region. 76 species (about 2.5 % of the total 2 685 vascular plant species in the region), in 6 families and 42 genera, were identified with C4 photosynthesis. 91 % of these C4 species belong to Monocotyledoneae, e.g. Cyperaceae (14 species), Gramineae (54 species), and Commelinaceae (1 species). Of these C4 species, Gramineae was the leading C4 family: 54 C4 grass species (71 % of the total C4 species), about 36 % of the total grasses, were identified in the TGP region. 98 % C4 species was found in therophyte (55 %) and hemicryptophyte (43 %). This is consistent with high grass and sedge compositions in the region. Most habitats of more than a half of these C4 species (65 %) will be submerged permanently, but no species will be endangered or extinct, because 95 % C4 species can be found from 500 to 800 m above sea level. The abundance of some C4 species will be dropped due to the reduction of distribution scope. It will take a long-term to explore the effects of the TGP on plants, vegetation, and environment.
The photosynthetic activities of three planktonic desmid species (Staurastrum brachiatum, Staurodesmus cuspidatus var. curvatus, and Staurastrum chaetoceras) were compared after adaptation to medium enriched with either a 20 mM Na+-phosphate (P) or HEPES buffer. Incubations up to 2 d were carried out at pH 6 or 8 under normal air or air enriched with 5 % CO2. Gross maximum photosynthetic rate (Pmax) and growth rate were decreased in both S. brachiatum and Std. cuspidatus at higher pH when using the HEPES buffer and this effect was independent of CO2 concentration, indicating that pH had an inhibitory effect on photosynthesis and growth in these species. The P-buffer at pH 8 caused a large decrease in Pmax and quantum yield for charge separation in photosystem 2 (PS2), compared to HEPES-buffered algae. This effect was very large in both S. brachiatum and Std. cuspidatus, two species characteristic of soft water lakes, but also significant in S. chaetoceras, a species dominant in eutrophic, hard water lakes. The decreased Pmax in P-buffer could not be related to a significant increase in cellular P content known to be responsible for inhibition in isolated chloroplasts. Experiments at pH 6 and 8 showed that two conditions, high pH and high Na+ concentration, both contributed to the decreased Pmax and quantum yield in the desmids. Effects of a P-buffer were less pronounced by using K+-P buffer. The use of P-buffer at pH 8 possibly resulted in high irradiance stress in all species, indicated by damage in the PS2 core complex. In the soft water species pH 8 resulted in increased non-photochemical quenching together with a high de-epoxidation state of the xanthophyll cycle pigments. and E. Spijkerman ... [et al.].