Metabolism of L-threonate, an ascorbate degradation product, requires a protein with L-threonate metabolizing domains in Arabidopsis.

L-Threonate is one of the major degradation products of ascorbate in plants. While bacteria can utilize L-threonate as a sole carbon source by converting it to dihydroxyacetone phosphate, a glycolysis intermediate, through a three- or four-step metabolic pathway, the corresponding processes in plants remain uncharacterized. Remarkably, an Arabidopsis gene encodes a unique protein containing domains homologous to all three enzymes involved in the bacterial three-step pathway.

The rice BRITTLE CULM 4 gene encodes a membrane protein involved in cellulose synthesis in the secondary cell wall.

The formation of secondary cell walls, which provide mechanical strength to the plant body, depends on numerous factors. Studies on rice brittle culm (bc) mutants allow us to identify these factors and gain insights into the mechanisms of secondary cell wall formation. Rice bc4 is a recessive bc mutant with fragile culms and leaves, similar to other bc mutants.

The deficiency of methylglyoxal synthase promotes cell proliferation in sp. PCC 6803 under mixotrophic conditions.

Methylglyoxal synthase (MGS), which converts dihydroxyacetone phosphate to methylglyoxal (MG), is found in only prokaryotes. sp. PCC 6803 possesses the gene , which encodes MGS.

Metabolic diversity analysis and genome wide assessment of oxalate accumulation in the leaves of rice () cultivars.

Soluble oxalate accumulates in rice leaves, and it causes mineral deficiency and urinary syndrome in livestock that consume the leaves. In our previous study, we found that the oxalate content was higher in the leaves of Koshihikari ( type cultivar) than in those of Takanari ( type cultivar). This difference was seen even when the two cultivars were grown under a high CO concentration, which inhibits oxalate synthesis via photorespiration, suggesting that the difference resulted from genetic factors rather than environmental factors.

Metabolic changes associated with dark-induced leaf senescence in Arabidopsis mutants.

Arabidopsis NADK2 (NAD kinase 2) is a chloroplast-localized enzyme involved in NADP synthesis, which acts as the final electron acceptor in the photosynthetic electron transfer chain. The NADK2-deficient mutant (nadk2) was used to analyze the effect of NAD(P)(H) unbalance in the dark-induced leaf senescence. During senescence, WT plants and nadk2 mutants showed a similar reduction in chlorophyll content.

Loss of peroxisomal NAD kinase 3 (NADK3) affects photorespiration metabolism in Arabidopsis.

Nicotinamide adenine dinucleotides (NAD and NADP) are electron mediators involved in various metabolic pathways. NADP(H) are produced by NAD kinase (NADK) through the phosphorylation of NAD(H). The Arabidopsis NADK3 (AtNADK3) is reported to preferentially phosphorylate NADH to NADPH and is localized in the peroxisome.

Dynamic seasonal changes in photosynthesis systems in leaves of Asarum tamaense, an evergreen understorey herbaceous species.

Background And Aims: Evergreen herbaceous species in the deciduous forest understorey maintain their photosystems in long-lived leaves under dynamic seasonal changes in light and temperature. However, in evergreen understorey herbs, it is unknown how photosynthetic electron transport acclimates to seasonal changes in forest understorey environments, and what photoprotection systems function in excess energy dissipation under high-light and low-temperature environments in winter.

Methods: Here, we used Asarum tamaense, an evergreen herbaceous species in the deciduous forest understorey with a single-flush and long-lived leaves, and measured photosynthetic CO2 assimilation and electron transport in leaves throughout the year.

Metabolomic analysis of rice brittle culm mutants reveals each mutant- specific metabolic pattern in each organ.

Introduction: Plant cell walls play an important role in providing physical strength and defence against abiotic stress. Rice brittle culm (bc) mutants are a strength-decreased mutant because of abnormal cell walls, and it has been reported that the causative genes of bc mutants affect cell wall composition. However, the metabolic alterations in each organ of bc mutants have remained unknown.

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.

VND-INTERACTING2 effectively inhibits transcriptional activities of VASCULAR-RELATED NAC-DOMAIN7 through a conserved sequence.

An Arabidopsis NAC domain transcription factor VND-INTERACTING2 (VNI2) was originally isolated as an interacting protein with another NAC domain transcription factor, VASCULAR-RELATED NAC-DOMAIN7 (VND7), a master regulator of xylem vessel element differentiation. VNI2 inhibits transcriptional activation activity of VND7 by forming a protein complex. Here, to obtain insights into how VNI2 regulates VND7, we tried to identify the amino acid region of VNI2 required for inhibition of VND7.

Arabidopsis nitrate-induced aspartate oxidase gene expression is necessary to maintain metabolic balance under nitrogen nutrient fluctuation.

Nitrate is a nutrient signal that regulates growth and development through NLP transcription factors in plants. Here we identify the L-aspartate oxidase gene (AO) necessary for de novo NAD biosynthesis as an NLP target in Arabidopsis. We investigated the physiological significance of nitrate-induced AO expression by expressing AO under the control of the mutant AO promoter lacking the NLP-binding site in the ao mutant.

An Arabidopsis NAC domain transcriptional activator VND7 negatively regulates expression.

A NAC domain transcription factor, VND-INTERACTING2 (VNI2) is originally isolated as an interacting protein with another NAC domain transcription factor, VASCULAR-RELATED NAC-DOMAIN7 (VND7), a master regulator of xylem vessel element differentiation. VND7 directly or indirectly induces expression of a number of genes associated with xylem vessel element differentiation, while VNI2 inhibits the transcriptional activation activities of VND7 by forming a protein complex. is expressed at an earlier stage of xylem vessel element differentiation than .

Change in expression levels of NAD kinase-encoding genes in Flaveria species.

Nicotinamide adenine dinucleotides (NAD(H)) and NAD phosphates (NADP(H)) are electron carriers involved in redox reactions and metabolic processes in all organisms. NAD kinase (NADK) is the only enzyme that phosphorylates NAD into NADP, using ATP as a phosphate donor. In NADP-dependent malic enzyme (NADP-ME)-type C photosynthesis, NADP(H) are required for dehydrogenation by NADP-dependent malate dehydrogenase (NADP-MDH) in mesophyll cells, and decarboxylation by NADP-ME in bundle sheath cells.

The NAD Kinase Slr0400 Functions as a Growth Repressor in Synechocystis sp. PCC 6803.

NADP+, the phosphorylated form of nicotinamide adenine dinucleotide (NAD), plays an essential role in many cellular processes. NAD kinase (NADK), which is conserved in all living organisms, catalyzes the phosphorylation of NAD+ to NADP+. However, the physiological role of phosphorylation of NAD+ to NADP+ in the cyanobacterium Synechocystis remains unclear.

Redox regulation of NADP-malate dehydrogenase is vital for land plants under fluctuating light environment.

Many enzymes involved in photosynthesis possess highly conserved cysteine residues that serve as redox switches in chloroplasts. These redox switches function to activate or deactivate enzymes during light-dark transitions and have the function of fine-tuning their activities according to the intensity of light. Accordingly, many studies on chloroplast redox regulation have been conducted under the hypothesis that "fine regulation of the activities of these enzymes is crucial for efficient photosynthesis.

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.

Metabolome analysis of rice leaves to obtain low-oxalate strain from ion beam-mutagenised population.

Introduction: Rice leaves and stems, which can be used as rice straw for livestock feed, accumulate soluble oxalate. The oxalate content often reaches 5% of the dry weight leaves. Excess uptake of oxalate-rich plants causes mineral deficiencies in vertebrates, so it is important to reduce the oxalate content in rice leaves to produce high-quality rice straw.

Dehydroascorbate Reductases and Glutathione Set a Threshold for High-Light-Induced Ascorbate Accumulation.

Plants require a high concentration of ascorbate as a redox buffer for survival under stress conditions, such as high light. Dehydroascorbate reductases (DHARs) are enzymes that catalyze the reduction of DHA to ascorbate using reduced glutathione (GSH) as an electron donor, allowing rapid ascorbate recycling. However, a recent study using an Arabidopsis () triple mutant lacking all three genes (herein called ∆) did not find evidence for their role in ascorbate recycling under oxidative stress.

Plant-Unique / Isomerism of Long-Chain Base Unsaturation is Selectively Required for Aluminum Tolerance Resulting from Glucosylceramide-Dependent Plasma Membrane Fluidity.

/ isomerism of the Δ8 unsaturation of long-chain base (LCB) is found only in plant sphingolipids. This unique geometry is generated by sphingolipid LCB Δ8 desaturase SLD which produces both isomers at various ratios, resulting in diverse / ratios in plants. However, the biological significance of this isomeric diversity remains controversial.

High-yielding rice Takanari has superior photosynthetic response to a commercial rice Koshihikari under fluctuating light.

Leaves within crop canopies experience variable light over the course of a day, which greatly affects photosynthesis and crop productivity. Little is known about the mechanisms of the photosynthetic response to fluctuating light and their genetic control. Here, we examined gas exchange, metabolite levels, and chlorophyll fluorescence during the photosynthetic induction response in an Oryza sativa indica cultivar with high yield (Takanari) and a japonica cultivar with lower yield (Koshihikari).

Mitochondrial AOX Supports Redox Balance of Photosynthetic Electron Transport, Primary Metabolite Balance, and Growth in under High Light.

When leaves receive excess light energy, excess reductants accumulate in chloroplasts. It is suggested that some of the reductants are oxidized by the mitochondrial respiratory chain. Alternative oxidase (AOX), a non-energy conserving terminal oxidase, was upregulated in the photosynthetic mutant of , , which accumulated reductants in chloroplast stroma.

One of the NAD kinases, sll1415, is required for the glucose metabolism of Synechocystis sp. PCC 6803.

Pyridine nucleotides (NAD(P)(H)) are electron carriers that are the driving forces in various metabolic pathways. Phosphorylation of NAD(H) to NADP(H) is performed by the enzyme NAD kinase (NADK). Synechocystis sp.

Metabolic and biochemical responses of Potamogeton anguillanus Koidz. (Potamogetonaceae) to low oxygen conditions.

Oxygen availability in water is considered one of the most important factors for growth and productivity in aquatic submerged macrophytes. In the present study, the growth, stress responses, and metabolic changes in Potamogeton anguillanus Koidz. (Potamogetonaceae) were assessed after a 21-day exposure to low (hypoxia; dissolved oxygen, DO < 1 mg/L) or null (anoxia) oxygen concentrations in water.