Adjustment of light-responsive NADP dynamics in chloroplasts by stromal pH.

Cyclic electron transfer (CET) predominates when NADP is at basal levels, early in photosynthetic induction; however, the mechanism underlying the subsequent supply of NADP to fully drive steady-state linear electron transfer remains unclear. Here, we investigated whether CET is involved in de novo NADP supply in Arabidopsis thaliana and measured chloroplastic NADP dynamics to evaluate responsiveness to variable light, photochemical inhibitors, darkness, and CET activity. The sum of oxidized and reduced forms shows that levels of NADP and NAD increase and decrease, respectively, in response to light; levels of NADP and NAD decrease and increase in the dark, respectively.

Loss of chloroplast-localized NAD kinase causes ROS stress in Arabidopsis thaliana.

Chloroplast-localized NAD kinase (NADK2) is responsible for the production of NADP, which is an electron acceptor in the linear electron flow of photosynthesis. The Arabidopsis T-DNA-inserted mutant of NADK2 (nadk2) showed delayed growth and pale-green leaves under continuous light conditions. Under short-day conditions (8 h light / 16 h dark), the nadk2 mutant showed more severe growth inhibition.

Altered metabolism of chloroplastic NAD kinase-overexpressing Arabidopsis in response to magnesium sulfate supplementation.

Nicotinamide adenine dinucleotide (NAD)/NAD phosphate (NADPH) is essential for numerous redox reactions and serve as co-factors in multiple metabolic processes in all organisms. NAD kinase (NADK) is an enzyme involved in the synthesis of NADP from NAD and ATP. Arabidopsis NADK2 (AtNADK2) is a chloroplast-localizing enzyme that provides recipients of reducing power in photosynthetic electron transfer.

Measurement of Chloroplastic NAD Kinase Activity and Whole Tissue NAD Kinase Assay.

Nicotinamide adenine dinucleotide phosphate (NADP) synthesis requires nicotinamide adenine dinucleotide (NAD) kinase activity, substrate NAD and ATP. The NAD kinase responds to various environmental stimuli and its activity is regulated via various regulatory pathways, such as Ca-dependent and redox-dependent signals. Conventional NAD kinase assay has been useful to evaluate enzyme activity; however, recent reports revealed a dynamics of NADP pool (the sum of NADP and NADPH) under fluctuating light condition, indicating that the rate of NADP synthesis is not always determined by NAD kinase activity.

Inter-Organelle NAD Metabolism Underpinning Light Responsive NADP Dynamics in Plants.

Upon illumination, photosystem I in chloroplasts catalyzes light-driven electron transport from plastocyanin to ferredoxin, followed by the reduction of NADP to NADPH by ferredoxin:NADP reductase for CO fixation. At the beginning of photosynthesis, NADP supply control is dominated by NADP synthesis rather than being recycled from the Calvin cycle. Importantly, ferredoxin distributes electrons to NADP as well as to thioredoxins for light-dependent regulatory mechanisms, to cyclic electron flow for more adenosine triphosphate (ATP) production, and to several metabolites for reductive reactions.

Assessment of gamma radiation from a limited area of forest floor using a cumulative personal dosimeter.

To elucidate long term changes in gamma radiation from a limited region of interest of the forest floor, a simple monitoring procedure using a cumulative personal dosimeter (D-shuttle) was examined from 2016 to 2017. The test site was in a small forest in Abiko, Japan, where the initial radiocesium contamination from the Fukushima Dai-ichi Nuclear Power Plant was 60-100 kBq m. Three experimental plots basically containing a set of two 5 × 5 m observation areas were arranged at the site.

Detection of Disulfides in Protein Extracts of using Monobromobimane (mBB).

Thiol-disulfide exchange is a key posttranslational modification, determining the folding process of intra- and inter-protein structures. Thiols can be detected by colorimetric reagents, which are stoichiometrically reduced by free thiols, and by fluorescent adducts, showing fluorescence only after thioester formation. We adapted a simple three-step method for detection of disulfide bonds in proteins.

Ferredoxin/thioredoxin system plays an important role in the chloroplastic NADP status of Arabidopsis.

NADP is a key electron carrier for a broad spectrum of redox reactions, including photosynthesis. Hence, chloroplastic NADP status, as represented by redox status (ratio of NADPH to NADP ) and pool size (sum of NADPH and NADP ), is critical for homeostasis in photosynthetic cells. However, the mechanisms and molecules that regulate NADP status in chloroplasts remain largely unknown.

Increased Rate of NAD Metabolism Shortens Plant Longevity by Accelerating Developmental Senescence in Arabidopsis.

NAD is a well-known co-enzyme that mediates hundreds of redox reactions and is the basis of various processes regulating cell responses to different environmental and developmental cues. The regulatory mechanism that determines the amount of cellular NAD and the rate of NAD metabolism remains unclear. We created Arabidopsis thaliana plants overexpressing the NAD synthase (NADS) gene that participates in the final step of NAD biosynthesis.

Radiocesium contamination in living and dead foliar parts of Japanese cedar during 2011-2015.

Radiocesium (Cs) activity concentrations, mainly derived from the Fukushima accident of March 2011, were measured in green foliar parts without separation by age (bulk green foliar parts; GL) and litterfall (LF) of Japanese cedar (Cryptomeria japonica) from 2011 to 2015. In all samples, Cs concentrations decreased exponentially over time, but were always higher in LF (7.36-0.

Disparate radiocesium leaching from two woody species by acceleration of litter decomposition using microbial inoculation.

Studies focusing on the migration of radionuclides in the forest floor have demonstrated that the ecological half-life of radiocesium on organic layer containing the debris of plant litter with various fungi and microorganisms is shorter than that in the deeper soil zone, suggesting that the litter decomposition affects radiocesium mobilization. Here, we showed the involvement of lignin, one of the major cell wall components of plant litter, in the fate of contaminated radiocesium during the process of fungal litter decomposition. In this study, litter decomposition of two different woody species, broadleaf deciduous Japanese cherry consisted of hardwood lignin and coniferous evergreen Japanese cedar with softwood lignin, were accelerated by in vitro fungal inoculation.

Changes in radiocesium contamination from Fukushima in foliar parts of 10 common tree species in Japan between 2011 and 2013.

Yearly changes in radiocesium ((137)Cs) contamination, primarily due to the Fukushima accident of March 2011, were observed in the foliar parts of 10 common woody species in Japan (Chamaecyparis obtusa, Cedrus deodara, Pinus densiflora, Cryptomeria japonica, Phyllostachys pubescens, Cinnamomum camphora, Metasequoia glyptostroboides, Prunus × yedoensis, Acer buergerianum, and Aesculus hippocastanum). The samples were obtained from Abiko (approximately 200 km SSW of the Fukushima Dai-ichi Nuclear Power Plant) during each growing season between 2011 and 2013, and the foliar parts were examined based on their year of expansion and location in each trees. The radiocesium concentrations generally decreased with time; however, the concentrations and rates of decrease varied among species, age of foliar parts, and locations.

A time dependent behavior of radiocesium from the Fukushima-fallout in litterfalls of Japanese flowering cherry trees.

Radiocesium ((134)Cs + (137)Cs) concentrations, primarily derived from the Fukushima accident in March 2011, were measured in litterfalls and green leaves of Japanese flowering cherry trees (Prunus x yedoensis cv. Somei-Yoshino). The sampling was performed mainly during the defoliation season in 2011 and 2012 using traps to collect litterfalls before contact with the ground.

A kinetic analysis of cadmium accumulation in a Cd hyper-accumulator fern, Athyrium yokoscense and tobacco plants.

Cadmium (Cd) accumulations in a Cd hyper-accumulator fern, Athyrium yokoscense (Ay), and tobacco, Nicotiana tabacum (Nt), were kinetically analysed using the positron-emitting tracer imaging system under two medium conditions (basal and no-nutrient). In Ay, maximumly 50% and 15% of the total Cd accumulated in the distal roots and the shoots under the basal condition, respectively. Interestingly, a portion of the Cd in the distal roots returned to the medium.

Real-time N2O gas detection system for agricultural production using a 4.6-µm-band laser source based on a periodically poled LiNbO3 ridge waveguide.

This article describes a gas monitoring system for detecting nitrous oxide (N2O) gas using a compact mid-infrared laser source based on difference-frequency generation in a quasi-phase-matched LiNbO3 waveguide. We obtained a stable output power of 0.62 mW from a 4.

NAD⁺ accumulation as a metabolic off switch for orthodox pollen.

Terrestrial plant pollen is classified into two categories based on its metabolic status: pollen with low-metabolism are termed "orthodox" and pollen with high-metabolism are termed "recalcitrant." Nicotinamide adenine dinucleotide (NAD) is crucial for a number of metabolisms in all extant organisms. It has recently been shown that NAD homeostasis plays an important role in a broad range of developmental processes and responses to environment.

NAD+ accumulation during pollen maturation in Arabidopsis regulating onset of germination.

Although the nicotinamide nucleotides NAD(H) and NADP(H) are essential for various metabolic reactions that play major roles in maintenance of cellular homeostasis, the significance of NAD biosynthesis is not well understood. Here, we investigated the dynamics of pollen nicotinamide nucleotides in response to imbibition, a representative germination cue. Metabolic analysis with capillary electrophoresis electrospray ionization mass spectrometry revealed that excess amount of NAD+ is accumulated in freshly harvested dry pollen, whereas it dramatically decreased immediately after contact with water.

Radiocesium contaminations of 20 wood species and the corresponding gamma-ray dose rates around the canopies at 5 months after the Fukushima nuclear power plant accident.

Radiocesium ((134)Cs + (137)Cs) deposition from the Fukushima nuclear power plant accident was measured in 20 woody plants (12 evergreen and 8 deciduous species) grown in Abiko (approximately 200 km SSW from the NPP). Leaves (needles) and twigs were sampled from each of three foliar positions (top, middle, and bottom) in the plant canopy in early August 2011. At the time, soils around the plants were also sampled, and gamma radiation dose rates were measured at each sampling position.

Temperature controls nuclear import of Tam3 transposase in Antirrhinum.

It has been proposed that environmental stimuli can activate transposable elements (TEs), whereas few substantial mechanisms have been shown so far. The class-II element Tam3 from Antirrhinum majus exhibits a unique property of low-temperature-dependent transposition (LTDT). LTDT has proved invaluable in developing the gene isolation technologies that have underpinned much of modern plant developmental biology.

Nicotinate/nicotinamide mononucleotide adenyltransferase-mediated regulation of NAD biosynthesis protects guard cells from reactive oxygen species in ABA-mediated stomatal movement in Arabidopsis.

Nicotinamide adenine dinucleotide (NAD) and its derivative nicotinamide adenine dinucleotide phosphate (NADP) are indispensable co-factors in broad-spectrum metabolic events for the maintenance of cellular homeostasis in all living organisms. In this study, the cellular expression levels of NAD biosynthesis genes in Arabidopsis were investigated. A very high expression of nicotinate/nicotinamide mononucleotide adenyltransferase (NMNAT) was observed in the differentiated stomatal guard cells of the leaf surface.

Metabolome and photochemical analysis of rice plants overexpressing Arabidopsis NAD kinase gene.

The chloroplastic NAD kinase (NADK2) is reported to stimulate carbon and nitrogen assimilation in Arabidopsis (Arabidopsis thaliana), which is vulnerable to high light. Since rice (Oryza sativa) is a monocotyledonous plant that can adapt to high light, we studied the effects of NADK2 expression in rice by developing transgenic rice plants that constitutively expressed the Arabidopsis chloroplastic NADK gene (NK2 lines). NK2 lines showed enhanced activity of NADK and accumulation of the NADP(H) pool, while intermediates of NAD derivatives were unchanged.

Pleiotropic modulation of carbon and nitrogen metabolism in Arabidopsis plants overexpressing the NAD kinase2 gene.

Nicotinamide nucleotides (NAD and NADP) are important cofactors in many metabolic processes in living organisms. In this study, we analyzed transgenic Arabidopsis (Arabidopsis thaliana) plants that overexpress NAD kinase2 (NADK2), an enzyme that catalyzes the synthesis of NADP from NAD in chloroplasts, to investigate the impacts of altering NADP level on plant metabolism. Metabolite profiling revealed that NADP(H) concentrations were proportional to NADK activity in NADK2 overexpressors and in the nadk2 mutant.

The role of NAD biosynthesis in plant development and stress responses.

Background: Pyridine nucleotides are essential for electron transport and serve as co-factors in multiple metabolic processes in all organisms. Each nucleotide has a particular role in metabolism. For instance, the NAD/NADP ratio is believed to be responsible for sustaining the functional status of plant cells.

Arabidopsis thaliana nicotinate/nicotinamide mononucleotide adenyltransferase (AtNMNAT) is required for pollen tube growth.

While mammals and fungi possess nicotinate/nicotinamide mononucleotide adenyltransferase (NMNAT) isoforms, Arabidopsis thaliana only contains a single NMNAT gene, AtNMNAT (At5g55810). We analyzed the enzymatic activity of the AtNMNAT-encoded protein to determine the role of AtNMNAT in plant development. AtNMNAT catalyzed the synthesis of nicotinate adenine dinucleotide (NaAD) from nicotinate mononucleotide (NaMN) in the Preiss-Handler-dependent pathway, and of nicotinamide adenine dinucleotide (NAD) from nicotiamide mononucleotide (NMN) in the Preiss-Handler-independent pathway.