Arthrospira maxima is unique among cyanobacteria, growing at alkaline pH (<11) in concentrated (bi)carbonate (1.2 M saturated) and lacking carbonic anhydrases. We investigated dissolved inorganic carbon (DIC) roles within PSII of A. maxima cells oximetrically and fluorometrically, monitoring the light reactions on the donor and acceptor sides of PSII. We developed new methods for removing DIC based on a (bi)carbonate chelator and magnesium for (bi)carbonate ionpairing. We established relative affinities of three sites: the water-oxidizing complex (WOC), non-heme iron/QA-, and solvent-accessible arginines throughout PSII. Full reversibility is achieved but (bi)carbonate uptake requires light. DIC depletion at the non-heme iron site and solvent-accessible arginines greatly reduces the yield of O2 due to O2 uptake, but accelerates the PSII-WOC cycle, specifically the S2-S3 and S3-S0 transitions. DIC removal from the WOC site abolishes water oxidation and appears to influence free energy stabilization of the WOC from a site between CP43-R357 and Ca2+., G. Ananyev, C. Gates, G. C. Dismukes., and Obsahuje bibliografické odkazy
The Chinese white pine beetle, Dendroctonus armandi Tsai and Li is a native species of bark beetle and one of the most destructive in much of western China. Little is known about the characterization of the pheromones trans-verbenol and verbenone, and their functions in D. armandi are unknown. Electroantennogram tests (EAG) and olfactory assays (Y-tube assays) in the laboratory revealed that (1) trans-verbenol may be an anti-aggregation pheromone for male and an aggregation pheromone for female D. armandi and (2) female beetles are more attracted to controls (hexane) than low concentrations of verbenone and male beetles more attracted to controls than high concentrations of verbenone. Field trials indicated that the addition of verbenone to bait used to trap D. armandi remarkably decreased the efficiency of field trapping. These results indicate that verbenone is an anti-aggregation pheromone for male D. armandi. This research provides evidence of the role of verbenone among the different types of pheromones. The pheromone verbenone clearly could be used to protect healthy Chinese white pines., Mingzhen Zhao, Lulu Dai, Yaya Sun, Danyang Fu, Hui Chen., and Obsahuje bibliografii
Ultrafast time resolved emission spectra were measured in whole cells of a PSI-deficient mutant of Synechocystis sp. PCC 6803 at room temperature and at 77K to study excitation energy transfer and trapping. By means of a target analysis it was estimated that the terminal emitter of the phycobilisome, termed allophycocyanin 680, transfers its energy with a rate of (20 ps)-1 to PSII. This is faster than the intraphycobilisome energy transfer rates between a rod and a core cylinder, or between the core cylinders., A. M. Acuña, P. Van Alphen, R. Van Grondelle, I. H. M. Van Stokkum., and Obsahuje bibliografické odkazy
Tropical savanna ecosystems are extremely diverse and important for global carbon storage. In the state of Mato Grosso, tropical savanna (locally known as the Cerrado), turns from well-drained, upland areas into seasonally flooded areas within the Pantanal; however, the Cerrado and the Pantanal share many common tree species, such as Vochysia divergens, a flood-adapted tree native to the Amazon Basin, and Curatella americana, a tree, adapted native to the welldrained the Cerrado. We measured the photosynthetic light response of these species in the the Cerrado and the Pantanal over a 1-year period to determine how these species physiologically adjust to these hydrologically distinct habitats. We hypothesized that neither species would experience a significant decline in maximum, light-saturated photosynthetic rate (Pmax) in their naturalized habitat. Physiological performance of each species was generally higher in the habitat that they were adapted to; however, our data indicated that both species have broad tolerance for seasonal variations in hydrology, allowing them to tolerate seasonal drought during the dry season in the Cerrado, and seasonal flooding during the wet season in the Pantanal. In V. divergens, flexible water-use efficiency, higher specific leaf area (SLA), and a greater ability to adjust mass-based Pmax (Pmax,m) to variations in leaf N and P concentration appeared to be key traits for withstanding prolonged drought in the Cerrado. In C. americana, increases in SLA and higher nutrient-use efficiency appeared to be important in maintaining high rates of Pmax,m in the seasonally flooded Pantanal. Flexibility in physiology and resource-use efficiency may allow these species to survive and persist in habitats with broadly differing hydrology., H. J. Dalmagro, F. de A. Lobo, G. L. Vourlitis, Â. C. Dalmolin, M. Z. Antunes Jr., C. E. R. Ortíz, J. de S. Nogueira., and Obsahuje bibliografii
The effects of foliar spray of putrescine (Put; 8 mM) on chlorophyll (Chl) metabolism and xanthophyll cycle in cucumber seedlings were investigated under saline conditions of 75 mM NaCl. Exogenous Put promoted the conversion of uroporhyrinogen III to protoporphyrin IX and alleviated decreases in Chl contents and in a size of the xanthophyll cycle pool under salt stress. Moreover, the Put treatment reduced the activities of uroporphyrinogen III synthase, chlorophyllase, and Mg-dechelatase and downregulated the transcriptional levels of glutamyl-tRNA reductase, 5-aminolevulinate dehydratase, uroporphyrinogen III synthase, uroporphyrinogen III decarboxylase, and chlorophyllide a oxygenase, but significantly increased the expression levels of non-yellow coloring 1-like, pheide a oxygenase, red chlorophyll catabolite reductase, and violaxanthin de-epoxidase. Taken together, these results suggest that Put might improve Chl metabolism and xanthophyll cycle by regulating enzyme activities and mRNA transcription levels in a way that improved the salt tolerance of cucumber plants., R. N. Yuan, S. Shu, S. R. Guo, J. Sun, J. Q. Wu., and Obsahuje bibliografii
Physiological traits, which are positively associated with yield under salt-stress conditions, can be useful selection criteria in screening for salt tolerance. We examined whether chlorophyll (Chl) content can be used as screening criterion in wheat. Our study involved 5 wheat genotypes under both saline and nonsaline field conditions as well as in a sand-culture experiment. Salt stress reduced significantly biomass, grain yield, total Chl and both Chl a and b in all genotypes. In the sand-culture experiment, Chl accumulation was higher in PF70354/BOW, Ghods, and H499.71A/JUP genotypes at nonsaline control, moderate, and high salt concentrations, respectively. In the field experiment, genotype H499.71A/JUP belonged to those with the highest Chl density. The SPAD (Soil Plant Analysis Development) meter readings were linearly related to Chl content both in the sand-culture and in the field experiment. However, salt stress affected the calibration of SPAD meter. Therefore, separate Chl-SPAD equations were suggested for saline and nonsaline conditions. The correlation coefficients between the grain yield and SPAD were positive and significant both in the sand culture and in the field experiment. These findings suggested that SPAD readings could be used as a tool for rapid assessment of relative Chl content in wheat genotypes. It could be used for the indirect selection of high-yielding genotypes of wheat under saline condition in sand-culture and field experiments., A. Kiani-Pouya, F. Rasouli., and Obsahuje bibliografii
The purpose of this study was to investigate the possible relationship between Toxoplasma gondii (Nicolle et Manceaux, 1908) and stuttering. We investigated the seropositivity rate for anti-T. gondii IgG and antibodies by enzyme-linked immunosorbent assay (ELISA) in stuttering children to ascertain a possible relationship between T. gondii infection and stuttering. We selected 65 stuttering children and 65 control children (non-stutterers) to investigate the seropositivity rate of anti-T. gondii antibodies by ELISA. Cranial magnetic resonance imaging (MRI) and scalp electroencephalography (EEG) were also performed in stuttering children. The seropositivity rate of anti-T. gondii IgG antibodies among stuttering children (28%) was significantly higher than in control group (5%; p = 0.001). No abnormality was detected in cranial MRI's of stutttering children and their EEG recordings were also normal. There was no significant difference in seropositivity rate regarding age, genders and residence area. The association between seroprevalence of infection with T. gondii and stuttering may be due to hyperdopaminergic state in brains of patients who are T. gondii-seropositive. Thus, there might be a causal relationship between toxoplasmosis and stuttering., Tuncay Çelik, Cem Gökçen, Özgür Aytaş, Aysima Özçelik, Mustafa Çelik, Nurdan Çoban., and Obsahuje bibliografii
Red alga contains four extrinsic proteins in photosystem II (PSII), which are PsbO, PsbV, PsbU, and PsbQ′. Except for the PsbQ′, the composition is the same in cyanobacterial PSII. Reconstitution analysis of cyanobacterial PSII has shown that oxygen-evolving activity does not depend on the presence of PsbQ′. Recently, the structure of red algal PSII was elucidated. However, the role of PsbQ′ remains unknown. In this study, the function of the acceptor side of PSII was analyzed in PsbQ′-reconstituted PSII by redox titration of QA and thermoluminescence. The redox potential of QA was positively shifted when PsbQ′ was attached to the PSII. The positive shift of QA is thought to cause a decrease in the amount of triplet chlorophyll in PSII. On the basis of these results, we propose that PsbQ′ has a photoprotective function when irradiated with strong light., M. Yamada, R. Nagao, M. Iwai, Y. Arai, A. Makita, H. Ohta, T. Tomo., and Obsahuje bibliografické odkazy
The aim of this study was to determine the effects of insulin infusion on oxidative stress induced by acute changes in glycemia in non-stressed hereditary hypertriglyceridemic rats (hHTG) and Wistar (control) rats. Rats were treated with glucose and either insulin or normal saline infusion for 3 hours followed by 90 min of hyperglycemic (12 mmol/l) and 90 min of euglycemic (6 mmol/l) clamp. Levels of total glutathione (GSH), oxidized glutathione (GSSG) and total antioxidant capacity (AOC) were determined to assess oxidative stress. In steady states of each clamp, glucose infusion rate (GIR) was calculated for evaluation of insulin sensitivity. GIR (mg.kg-1.min-1) was significantly lower in hHTG in comparison with Wistar rats; 25.46 (23.41 - 28.45) vs. 36.30 (27.49 - 50.42) on glycemia 6 mmol/l and 57.18 (50.78 - 60.63) vs. 68.00 (63.61 - 85.92) on glycemia 12 mmol/l. GSH/GSSG ratios were significantly higher in hHTG rats at basal conditions. Further results showed that, unlike in Wistar rats, insulin infusion significantly increases GSH/GSSG ratios in hHTG rats: 10.02 (9.90 - 11.42) vs. 6.01 (5.83 - 6.43) on glycemia 6 mmol/l and 7.42 (7.15 - 7.89) vs. 6.16 (5.74 - 7.05) on glycemia 12 mmol/l. Insulin infusion thus positively influences GSH/GSSG ratio and that way reduces intracellular oxidative stress in insulin-resistant animals., M. Žourek, P. Kyselová, J. Mudra, M. Krčma, Z. Jankovec, S. Lacigová, J. Víšek, Z. Rušavý., and Obsahuje bibliografii a bibliografické odkazy
The aim of this work was to determine two types of photosynthetic water-use efficiency in order to examine their utility as selection criteria for tolerance of energy crops to soil water deficit. Furthermore, effects of crop cultivation on soil water content and storage were investigated. Seven energy crops were examined: miscanthus, prairie cordgrass, willow, thorn-free rose, Virginia mallow, Bohemian knotweed, and topinambour. The highest values of instantaneous (WUE) and intrinsic (WUEi) water-use efficiencies were found for miscanthus and prairie cordgrass. The reduction of WUE and/or WUEi was caused mainly by a rapid rise in the transpiration rate and a greater stomatal conductance, respectively. Principal component analysis showed that neither WUE nor WUEi could be recommended as universal selection criteria for the drought tolerance in different energy crops. The proper localization of soil with a good supply of water is most the important condition for energy crop plantations., S. Podlaski, S. Pietkiewicz, D. Chołuj, T. Horaczek, G. Wiśniewski, D. Gozdowski, H. M. Kalaji., and Obsahuje bibliografii