Enzymatic and quantitative properties of Rubisco in some conifers and lycopods.

Information on the kinetic properties of Rubisco, a key enzyme for photosynthesis, is scarce in land plants that emerged early during the evolutionary process. This study examined the carboxylase activity and abundance of Rubisco in five conifers, two lycopods, and three control C crops. The turnover rates of Rubisco carboxylation (k) under saturated-CO conditions in conifers and lycopods were comparable to those in the control C crops.

Measuring the Release of Ammonia from Leaves.

Ammonia (NH) is released from the leaves to the atmosphere when atmospheric NH concentration is low; in contrast, when atmospheric NH concentration is high, NH in the atmosphere is absorbed by the leaves. Some previous studies have examined relationships of such NH gas exchange with photorespiration, because a NH production reaction is involved in the photorespiratory pathway. NH compensation point (χ) is known as a parameter that represents an NH emission potential of the leaves.

Equisetum praealtum and E. hyemale have abundant Rubisco with a high catalytic turnover rate and low CO affinity.

The kinetic properties of Rubisco, a key enzyme for photosynthesis, have been examined in numerous plant species. However, this information on some plant groups, such as ferns, is scarce. This study examined Rubisco carboxylase activity and leaf Rubisco levels in seven ferns, including four Equisetum plants (E.

Different photorespiratory mechanisms in conifer leaves, where peroxisomes have intrinsically low catalase activity.

Photorespiration is an essential metabolic mechanism associated with photosynthesis; however, little is known about the photorespiratory pathway of conifer gymnosperms. Metabolite analyses of the leaves of 27 tree species showed that the mean glycerate content in conifer leaves was lower than that in angiosperm leaves. We performed experiments where [ C]-serine was fed to detached shoots of a conifer (Cryptomeria japonica), via the transpiration stream, and compared the labeling patterns of photorespiratory metabolites with those of an angiosperm tree (Populus nigra), because glycerate is produced from serine via hydroxypyruvate in peroxisomes.

Effect of symbiotic N fixation on leaf protein contents, protein degradation and nitrogen resorption during leaf senescence in temperate deciduous woody species.

Nitrogen (N) resorption from senescing leaves enables plants to reuse N, making them less dependent on current N uptake from the environment, leading to higher fitness, particularly under low N supply. Species that form a symbiotic association with N-fixing bacteria have not evolved proficient N resorption, i.e.

Somatic Embryogenesis Initiation in Sugi (Japanese Cedar, D. Don): Responses from Male-Fertile, Male-Sterile, and Polycross-Pollinated-Derived Seed Explants.

This study aimed to obtain information from several embryogenic cell (EC) genotypes analyzing the factors that affect somatic embryogenesis (SE) initiation in sugi ( Cupressaceae) to apply them in the improvement of protocols for efficient induction of embryogenic cell lines (ECLs). The results of several years of experiments including studies on the influence of initial explant, seed collection time, and explant genotype as the main factors affecting SE initiation from male-fertile, male-sterile, and polycross-pollinated-derived seeds are described. Initiation frequencies depending on the plant genotype varied from 1.

Dehydroquinate dehydratase/shikimate dehydrogenases involved in gallate biosynthesis of the aluminum-tolerant tree species Eucalyptus camaldulensis.

Eucalyptus camaldulensis EcDQD/SDH2 and 3 combine gallate formation, dehydroquinate dehydratase, and shikimate dehydrogenase activities. They are candidates for providing the essential gallate for the biosynthesis of the aluminum-detoxifying metabolite oenothein B. The tree species Eucalyptus camaldulensis shows exceptionally high tolerance against aluminum, a widespread toxic metal in acidic soils.

Oxygen response of leaf CO compensation points used to determine Rubisco specificity factors of gymnosperm species.

Rubisco specificity factor (S), a measure of the relative capacities of an enzyme to catalyze carboxylation and oxygenation of ribulose-1,5-bisphosphate, determines the extent of photosynthetic CO assimilation and photorespiratory CO release. The current model of C3 photosynthesis, the Farquhar-von Caemmerer-Berry (FvCB) model, requires a species-specific S. However, S values have never been reported in conifers, likely because in vitro kinetic analysis of conifer Rubisco presents difficulties.

Effects of Elevated Atmospheric CO2 on Respiratory Rates in Mature Leaves of Two Rice Cultivars Grown at a Free-Air CO2 Enrichment Site and Analyses of the Underlying Mechanisms.

Respiratory CO2 efflux and O2 uptake rates in leaves change in response to the growth CO2 concentration ([CO2]). The degrees of change vary depending on the responses of cellular processes such as nitrogen (N) assimilation and accumulation of organic acids to growth [CO2]. However, the underlying mechanisms remain unclear.

Elevated CO2 decreases the Photorespiratory NH3 production but does not decrease the NH3 compensation point in rice leaves.

The exchange of gaseous NH3 between the atmosphere and plants plays a pivotal role in controlling the global NH3 cycle. Photorespiration generates NH3 through oxygenation instead of carboxylation by the CO2-fixing enzyme, ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO). The future increase in the atmospheric CO2 concentration, [CO2], is expected to reduce plant NH3 production by suppressing RuBisCO oxygenation (Vo).

Sites of action of elevated CO2 on leaf development in rice: discrimination between the effects of elevated CO2 and nitrogen deficiency.

Elevated CO2 concentrations (eCO2) trigger various plant responses. Despite intensive studies of these responses, the underlying mechanisms remain obscure. In this work, we investigated when and how leaf physiology and anatomy are affected by eCO2 in rice plants.

Lessons from engineering a single-cell C(4) photosynthetic pathway into rice.

The transfer of C(4) plant traits into C(3) plants has long been a strategy for improving the photosynthetic performance of C(3) plants. The introduction of a pathway mimicking the C(4) photosynthetic pathway into the mesophyll cells of C(3) plants was only a realistic approach when transgenic technology was sufficiently well developed and widely adopted. Here an attempt to introduce a single-cell C(4)-like pathway in which CO(2) capture and release occur in the mesophyll cell, such as the one found in the aquatic plant Hydrilla verticillata (L.

Determination of the site of CO₂ sensing in poplar: is the area-based N content and anatomy of new leaves determined by their immediate CO₂ environment or by the CO₂ environment of mature leaves?

Exposure to an elevated CO(2) concentration ([CO(2)]) generally decreases leaf N content per unit area (N(area)) and stomatal density, and increases leaf thickness. Mature leaves can 'sense' elevated [CO(2)] and this regulates stomatal development of expanding leaves (systemic regulation). It is unclear if systemic regulation is involved in determination of leaf thickness and N(area)-traits that are significantly correlated with photosynthetic capacity.

Role of OsNPR1 in rice defense program as revealed by genome-wide expression analysis.

NPR1 is a central regulator of salicylic-acid (SA)-mediated defense signaling in Arabidopsis. Here, we report the characterization of OsNPR1, an Oryzae sativa (rice) ortholog of NPR1, focusing on its role in blast disease resistance and identification of OsNPR1-regulated genes. Blast resistance tests using OsNPR1 knockdown and overexpressing rice lines demonstrated the essential role of OsNPR1 in benzothiadiazole (BTH)-induced blast resistance.

Phosphoenolpyruvate carboxylase intrinsically located in the chloroplast of rice plays a crucial role in ammonium assimilation.

Phosphoenolpyruvate carboxylase (PEPC) is a key enzyme of primary metabolism in bacteria, algae, and vascular plants, and is believed to be cytosolic. Here we show that rice (Oryza sativa L.) has a plant-type PEPC, Osppc4, that is targeted to the chloroplast.

Metabolic turnover analysis by a combination of in vivo 13C-labelling from 13CO2 and metabolic profiling with CE-MS/MS reveals rate-limiting steps of the C3 photosynthetic pathway in Nicotiana tabacum leaves.

Understanding of the control of metabolic pathways in plants requires direct measurement of the metabolic turnover rate. Sugar phosphate metabolism, including the Calvin cycle, is the primary pathway in C(3) photosynthesis, the dynamic status of which has not been assessed quantitatively in the leaves of higher plants. Since the flux of photosynthetic carbon metabolism is affected by the CO(2) fixation rate in leaves, a novel in vivo (13)C-labelling system was developed with (13)CO(2) for the kinetic determination of metabolic turnover that was the time-course of the (13)C-labelling ratio in each metabolite.

Deactivation of aquaporins decreases internal conductance to CO diffusion in tobacco leaves grown under long-term drought.

We compared the diffusion conductance to CO from the intercellular air space to the chloroplasts (internal conductance (g )) between tobacco leaves acclimated to long-term drought (drought-acclimated (DA)) and those grown under sufficient irrigation (well-watered (WW)), and analysed the changes in g in relation to the leaf anatomical characteristics and a possible CO transporter, aquaporin. The g , which was estimated by combined analyses of CO gas exchange with chlorophyll fluorescence, in the DA plants was approximately half of that in the WW plants. The mesophyll and chloroplast surface areas exposing the intercellular air space, which potentially affect g , were not significantly different between the WW and DA plants.

Maintenance mechanisms of the pipe model relationship and Leonardo da Vinci's rule in the branching architecture of Acer rufinerve trees.

The pipe model relationship (constancy of branch cross-sectional area/leaf area) and Leonardo da Vinci's rule (equality of total cross-sectional area of the daughter branches and cross-sectional area of their mother branch) are empirical rules of tree branching. Effects of branch manipulation on the pipe model relationships were examined using five Acer rufinerve trees. Half the branches in each tree were untreated (control branches, CBs), and, for the others (manipulated branches, MBs), either light intensity or leaf area (both relating to photosynthetic source activity), or shoot elongation (source + sink activities), was reduced, and responses of the pipe model relationships were followed for 2 years.

Biosynthesis of astaxanthin in tobacco leaves by transplastomic engineering.

The natural pigment astaxanthin has attracted much attention because of its beneficial effects on human health, despite its expensive market price. In order to produce astaxanthin, transgenic plants have so far been generated through conventional genetic engineering of Agrobacterium-mediated gene transfer. The results of trials have revealed that the method is far from practicable because of low yields, i.

Effects of polyploidy on photosynthetic properties and anatomy in leaves of Phlox drummondii.

Polyploidy affects photosynthesis by causing changes in morphology, anatomy and biochemistry. However, in newly developed polyploids, the genome may be unstable. In this study, diploid (2×) and synthetic autotetraploids in initial (4×-C) and 11th generations (4×-C) of Phlox drummondii Hook were used to study the effects of chromosome doubling and genome stabilisation on leaf photosynthesis and anatomical properties.

Stomatal development in new leaves is related to the stomatal conductance of mature leaves in poplar (Populus trichocarpaxP. deltoides).

In general, stomatal density (SD) decreases when plants are grown at high CO2 concentrations. Recent studies suggest that signals produced from mature leaves regulate the SD of expanding leaves. To determine the underlying driver of these signals in poplar (Populus trichocarpaxP.

Construction and maintenance of the optimal photosynthetic systems of the leaf, herbaceous plant and tree: an eco-developmental treatise.

Background And Aims: The paper by Monsi and Saeki in 1953 (Japanese Journal of Botany 14: 22-52) was pioneering not only in mathematical modelling of canopy photosynthesis but also in eco-developmental studies of seasonal changes in leaf canopies.

Scope: Construction and maintenance mechanisms of efficient photosynthetic systems at three different scaling levels--single leaves, herbaceous plants and trees--are reviewed mainly based on the nitrogen optimization theory. First, the nitrogen optimization theory with respect to the canopy and the single leaf is briefly introduced.

Histone deacetylase inhibitor suppression of autoantibody-mediated arthritis in mice via regulation of p16INK4a and p21(WAF1/Cip1) expression.

Objective: To examine whether depsipeptide (FK228), a histone deacetylase (HDA) inhibitor, has inhibitory effects on the proliferation of synovial fibroblasts from rheumatoid arthritis (RA) patients, and to examine the effects of systemic administration of FK228 in an animal model of arthritis.

Methods: Autoantibody-mediated arthritis (AMA) was induced in 19 male DBA/1 mice (6-7 weeks old); 10 of them were treated by intravenous administration of FK228 (2.5 mg/kg), and 9 were used as controls.

Relationships between light, leaf nitrogen and nitrogen remobilization in the crowns of mature evergreen Quercus glauca trees.

We estimated the amount of nitrogen (N) remobilized from 1-year-old leaves at various positions in the crowns of mature Quercus glauca Thunb. ex Murray trees and related this to the production of new shoots. Leaf N concentration on an area basis (Na) and total N (Nt= Na x lamina area of all leaves on a shoot) were related to photosynthetic photon flux (PPF) on the leaves of current-year and 1-year-old shoots.