Biochemical response of hybrid black poplar tissue culture (Populus × canadensis) on water stress.

In this study, poplar tissue culture (hybrid black poplar, M1 genotype) was subjected to water stress influenced by polyethyleneglycol 6000 (100 and 200 mOsm PEG 6000). The aim of the research was to investigate the biochemical response of poplar tissue culture on water deficit regime. Antioxidant status was analyzed including antioxidant enzymes, superoxide-dismutase (SOD), catalase (CAT), guiacol-peroxidase (GPx), glutathione-peroxidase (GSH-Px), glutathione-reductase, reduced glutathione, total phenol content, Ferric reducing antioxidant power and DPPH radical antioxidant power. Polyphenol oxidase and phenylalanine-ammonium-lyase were determined as enzymatic markers of polyphenol metabolism. Among oxidative stress parameters lipid peroxidation, carbonyl-proteins, hydrogen-peroxide, reactive oxygen species, nitric-oxide and peroxynitrite were determined. Proline, proline-dehydrogenase and glycinebetaine were measured also as parameters of water stress. Cell viability is finally determined as a biological indicator of osmotic stress. It was found that water stress induced reactive oxygen and nitrogen species and lipid peroxidation in leaves of hybrid black poplar and reduced cell viability. Antioxidant enzymes including SOD, GPx, CAT and GSH-Px were induced but total phenol content and antioxidant capacity were reduced by PEG 6000 mediated osmotic stress. The highest biochemical response and adaptive reaction was the increase of proline and GB especially by 200 mOsm PEG. While long term molecular analysis will be necessary to fully address the poplar potentials for water stress adaptation, our results on hybrid black poplar suggest that glycine-betaine, proline and PDH enzyme might be the most important markers of poplar on water stress and that future efforts should be focused on these markers and strategies to enhance their concentration in poplar.

Mesophyll conductance to CO2 and Rubisco as targets for improving intrinsic water use efficiency in C3 plants.

Water limitation is a major global constraint for plant productivity that is likely to be exacerbated by climate change. Hence, improving plant water use efficiency (WUE) has become a major goal for the near future. At the leaf level, WUE is the ratio between photosynthesis and transpiration. Maintaining high photosynthesis under water stress, while improving WUE requires either increasing mesophyll conductance (gm ) and/or improving the biochemical capacity for CO2 assimilation-in which Rubisco properties play a key role, especially in C3 plants at current atmospheric CO2 . The goals of the present analysis are: (1) to summarize the evidence that improving gm and/or Rubisco can result in increased WUE; (2) to review the degree of success of early attempts to genetically manipulate gm or Rubisco; (3) to analyse how gm , gsw and the Rubisco's maximum velocity (Vcmax ) co-vary across different plant species in well-watered and drought-stressed conditions; (4) to examine how these variations cause differences in WUE and what is the overall extent of variation in individual determinants of WUE; and finally, (5) to use simulation analysis to provide a theoretical framework for the possible control of WUE by gm and Rubisco catalytic constants vis-à-vis gsw under water limitations.

Diffusional limitations explain the lower photosynthetic capacity of ferns as compared with angiosperms in a common garden study.

Ferns are thought to have lower photosynthetic rates than angiosperms and they lack fine stomatal regulation. However, no study has directly compared photosynthesis in plants of both groups grown under optimal conditions in a common environment. We present a common garden comparison of seven angiosperms and seven ferns paired by habitat preference, with the aims of (1) confirming that ferns do have lower photosynthesis capacity than angiosperms and quantifying these differences; (2) determining the importance of diffusional versus biochemical limitations; and (3) analysing the potential implication of leaf anatomical traits in setting the photosynthesis capacity in both groups. On average, the photosynthetic rate of ferns was about half that of angiosperms, and they exhibited lower stomatal and mesophyll conductance to CO2 (gm ), maximum velocity of carboxylation and electron transport rate. A quantitative limitation analysis revealed that stomatal and mesophyll conductances were co-responsible for the lower photosynthesis of ferns as compared with angiosperms. However, gm alone was the most constraining factor for photosynthesis in ferns. Consistently, leaf anatomy showed important differences between angiosperms and ferns, especially in cell wall thickness and the surface of chloroplasts exposed to intercellular air spaces.

Non-invasive ventilation after extubation in patients with chronic obstructive airways disease: a randomised controlled trial.

Non-invasive positive pressure ventilation (NPPV) is a well established therapy for acute respiratory failure in patients with chronic obstructive pulmonary disease, however its role in post-extubation period is uncertain. The objective of this study was to find the effect of NPPV on rate of re-intubation, intensive care unit and hospital stay, and physiological parameters in severe chronic obstructive pulmonary disease patients after planned extubation. Forty patients with severe chronic obstructive pulmonary disease were randomised immediately after planned extubation to receive NPPV (n=20) or conventional therapy (n=20). NPPV was delivered with mean levels of inspiratory positive-airway pressure of 12.10 +/- 1.37 cmH2O and expiratory positive-airway pressure of 6.50 +/- 1.00 cmH2O for a mean period of 34.75 +/- 10 hours for 7 to 11 hours/day. Patients in conventional therapy group received usual treatment. Reintubation rate among NPPV (15%) and conventional (25%) were similar (P=0.44). The duration of intensive care unit stay after extubation (2.05 +/- 2.15 vs 1.55 +/- 0.82 days, P=0.34) and hospital stay (16.10 +/- 6.29 vs 18.25 +/- 7.91 days, P=0.34) in both groups were comparable. Given the load of chronic obstructive pulmonary disease patients and wide availability of NPPV it is safe to recommend its use in these patients soon after extubation, although clear benefit is not documented in this study.

Differences in root functions during long-term drought adaptation: comparison of active gene sets of two wheat genotypes.

In an attempt to shed light on the role of root systems in differential responses of wheat genotypes to long-term water limitation, transcriptional differences between two wheat genotypes (Triticum aestivum L., cv. Plainsman V and landrace Kobomugi) were identified during adaptation to moderate water stress at the tillering stage. Differences in organ sizes, water-use efficiency and seed production were detected in plants grown in soil, and root functions were characterised by expression profiling. The molecular genetic background of the behaviour of the two genotypes during this stress was revealed using a cDNA macroarray for transcript profiling of the roots. During a 4-week period of moderate water deficit, a set of up-regulated genes displaying transiently increased expression was identified in young plantlets, mostly in the second week in the roots of Kobomugi, while transcript levels remained constantly high in roots of Plainsman V. These genes encode proteins with various functions, such as transport, protein metabolism, osmoprotectant biosynthesis, cell wall biogenesis and detoxification, and also regulatory proteins. Oxidoreductases, peroxidases and cell wall-related genes were induced significantly only in Plainsman V, while induction of stress- and defence-related genes was more pronounced in Kobomugi. Real-time qPCR analysis of selected members of the glutathione S-transferase gene family revealed differences in regulation of family members in the two genotypes and confirmed the macroarray results. The TaGSTZ gene was stress-activated only in the roots of Kobomugi.

Impact of an exceptionally hot dry summer on photosynthetic traits in oak (Quercus pubescens) leaves.

Climatic constraints on diurnal variations in photosynthetic traits were investigated in oaks (Quercus pubescens Willd.) growing in the Swiss Alps. The measurement period included the summer of 2003, when central Europe experienced a record-breaking heat wave. During the summer, a combination of moderate heat and drought caused a reduction in photosynthetic CO(2) assimilation rate (P(n)) by mid-morning, which increased by the afternoon. More extreme drought and heat caused a sharp day-long reduction in P(n). These effects were closely related to changes in stomatal conductance (g(s)), but low g(s) was unaccompanied by low intercellular CO(2) concentrations (C(i)). Around midday, a combination of heat and drought increased C(i), indicating metabolic limitation of photosynthesis. Chlorophyll a (Chl a) fluorescence measurements revealed reversible down-regulation of photosystem (PS) II activity during the day, which was accentuated by heat and drought and correlated with diurnal variation in zeaxanthin accumulation. A combination of heat and drought reduced leaf Chl a + b concentrations and increased ratios of total carotenoids, xanthophyll-cycle carotenoids and lutein to Chl a + b. The combination of summertime heat and drought altered the 77 K Chl fluorescence emission spectra of leaves, indicating changes in the organization of thylakoid membranes, but it had no effect on the amounts of the major light-harvesting Chl-a/b-binding protein of PSII (LHCII), Rubisco, Rubisco activase, Rubisco-binding protein (cpn-60), phosphoribulokinase and chloroplast ATP synthase. The results demonstrate that Q. pubescens can maintain photosynthetic capacity under adverse summer conditions.

High-light stress does not impair biomass accumulation of sun-acclimated tropical tree seedlings (Calophyllum longifolium Willd. and Tectona grandis L. f.).

Studies with seedlings of tropical rainforest trees ( Calophyllum longifolium Willd.; Tectona grandis L. f.) were designed to test whether high-light stress affects photosynthetic performance and growth. Seedlings were cultivated in pots at a field site in Central Panama (9 degrees N) and separated into two groups: (1) plants exposed to full solar radiation; (2) plants subjected to automatic neutral shading (48 %) whenever visible irradiance surpassed 1000, 1200, or 1600 micromol photons m-2 s-1. After 2-4 months, chlorophyll fluorescence (Fv/Fm ratio), photosynthetic net CO2 uptake, pigment composition, alpha-tocopherol content of leaves, and plant biomass accumulation were measured. Fully sun-exposed, compared to periodically shaded plants, experienced substantial high-light stress around midday, indicated by photoinhibition of photosystem II and depressed net CO2 uptake. Higher contents of xanthophyll cycle pigments, lutein, and alpha-tocopherol showed an enhancement of photoprotection in fully sun-exposed plants. However, in all experiments, the maximum capacity of net CO2 uptake and plant dry mass did not differ significantly between the two treatments. Thus, in these experiments, high-light stress did not impair productivity of the seedlings studied. Obviously, the continuously sun-exposed plants were capable of fully compensating for any potential costs associated with photoinhibition and repair of photosystem II, reduced CO2 assimilation, and processes of high-light acclimation.

Leukemia inhibitory factor by systemic administration rescues spinal motor neurons in the SOD1 G93A murine model of familial amyotrophic lateral sclerosis.

Leukemia inhibitory factor (LIF) is a survival factor for motoneurons. In this study we investigated whether intense systemic LIF therapy prevents the loss of lumbar motoneurons in the transgenic SOD1 G93A mouse model of familial amyotrophic lateral sclerosis. Treatment involved daily 25 microg/kg intraperitoneal injection for a period of 6 weeks starting at 70 days of age. Using the unbiased optical dissector technique, significant rescue of motoneurons in the LIF-treated group (3809+/-455) was found compared to the vehicle group (1085+/-140).

Isolation: analysis and properties of three bradykinin-potentiating peptides (BPP-II, BPP-III, and BPP-V) from Bothrops neuwiedi venom.

In the course of systematic investigations on low-molecular-weight compounds from the venom of Crotalidae and Viperidae, we have isolated and characterized at least three bradykinin-potentiating peptides (BPP-II, BPP-III, and BPP-V) from Bothrops neuwiedi venom by gel filtration on Sephadex G-25 M, Sephadex G-10 followed by HPLC. The peptides showed bradykinin-potentiating action on isolated guinea-pig ileum, for which the BPP-V was more active than of BPP-II, and BPP-III, rat arterial blood pressure, and a relevant angiotensin-converting enzyme (ACE) competitive inhibiting activity. The kinetic studies showed a Ki of the order of 9.7 x 10(-3) microM to BPP-II, 7 x 10(-3) microM to BPP-III, and 3.3 x 10(-3) microM to BPP-V. The amino acid sequence of the BPP-III has been determined to be pGlu-Gly-Gly-Trp-Pro-Arg-Pro-Gly-Pro-Glu-Ile-Pro-Pro, and the amino acid compositions of the BPP-II and BPP-V by amino acid analysis were 2Glu-2Gly-1Arg-4Pro-1Ile and 2Glu-2Gly-1Ser-3Pro-2Val-1Ile, with molecular weight of 1372, 1046, and 1078, respectively.

Biosynthesis of gamma-linolenic acid in developing seeds of borage (Borago officinalis L.).

delta 6-desaturation of [14C]linoleoyl-CoA or [14C]oleoyl-CoA leading to the synthesis of gamma-linolenic acid was studied in vitro with microsomal fractions from developing seeds of Borago officinalis. Time course of the reaction, effects of protein and precursor concentrations and nucleotide requirements were examined. These parameters allowed us to improve the in vitro delta 6-desaturation assay. We observed that the precursors were acylated mainly in phosphatidylcholine, diacylglycerol and triacylglycerol, and then desaturated. NADH was absolutely required when [14C]oleoyl-CoA was the precursor, but not when [14C]linoleoyl-CoA was the precursor although it stimulated the reaction. The in vitro delta 6-desaturase activity was found mainly in phosphatidylcholine, associated with enriched endoplasmic reticulum membranes (ER) from embryos. No activity was observed in ER from seed coat or seedling. During maturation of the seeds, delta 6-desaturase reached its highest activity 14 to 16 days after pollination.

N-terminal sequences of oat avenins compared to other cereal prolamins.

Like the alcohol-soluble seed storage proteins (also called prolamins) of other cereals, avenins, the oat prolamins, are a series of polymorphic molecules belonging to a multigenic family stored within the protein bodies of the starchy endosperm. Nevertheless, they exhibit some pecularities: among the seed storage proteins, their proportion is low compared to prolamins from other cereal species; their net charge is higher; the amount of Gln + Pro only reaches 49 mol%; they are less polymorphic. We have isolated and purified several avenins and sequenced their N-terminal end. The microheterogeneity and the pecularity of avenins are revealed by the comparison of the N-terminal sequences. Like other prolamins, they exhibit tandem repeats; these repetitive peptides are slightly different from those of other prolamins of the Festucoideae, and the repetition begins earlier in the sequence. As for prolamins from other species, their predicted secondary structure reveals successive beta-turns which might be arranged in a pseudo-helix structure.

Purification and properties of plant cytochrome b5.

Microsomal cytochrome b5 was 352-fold purified from potato tubers with a yield of 10.4%. To our knowledge, this is the first report relating the purification of higher-plant cytochrome b5. Its Mr (16 700) and absorption spectrum are similar to those of animal and yeast cytochrome b5.

Purification of a NADH-ferricyanide reductase from plant microsomal membranes with a zwitterionic detergent.

A microsomal NADH-ferricyanide reductase was purified to homogeneity from potato tubers. A zwitterionic detergent (CHAPS) was used for the extraction of this reductase which is the first to be purified from plant microsomal membranes. The successive steps of purification included an anion exchange column (DEAE-cellulose or DEAE-Trisacryl), a blue-Ultrogel affinity column and a gel filtration on Sephadex G75. The purification factor was 280 and the yield was 1.6%. The protein has an apparent molecular weight of 44,000 +/- 1,000 as estimated from SDS-PAGE. This successful purification opens new perspectives in the study of oleate desaturase of higher plants which is assumed to contain NADH-ferricyanide reductase as an essential component.