Exogenous ethanol treatment alleviates oxidative damage of under conditions of high-light stress.

Abiotic stresses, such as high light and salinity, are major factors that limit crop productivity and sustainability worldwide. Chemical priming is a promising strategy for improving the abiotic stress tolerance of plants. Recently, we discovered that ethanol enhances high-salinity stress tolerance in and rice by detoxifying reactive oxygen species (ROS).

CP12 Is Involved in Protection against High Light Intensity by Suppressing the ROS Generation in PCC7942.

We previously reported that CP12 formed a complex with GAPDH and PRK and regulated the activities of these enzymes and the Calvin-Benson cycle under dark conditions as the principal regulatory system in cyanobacteria. More interestingly, we found that the cyanobacterial CP12 gene-disrupted strain was more sensitive to photo-oxidative stresses such as under high light conditions and paraquat treatment. When a mutant strain that grew normally under low light was subjected to high light conditions, decreases in chlorophyll and photosynthetic activity were observed.

Sugar Transporter Protein 1 (STP1) contributes to regulation of the genes involved in shoot branching via carbon partitioning in Arabidopsis.

We previously demonstrated that alterations in sugar partitioning affect the expression of genes involved in hormone biosynthesis and responses, including BRANCHED1 (BRC1), resulting in enhanced shoot branching in transgenic Arabidopsis plants overexpressing cyanobacterial fructose-1,6-bisphosphatase-II in the cytosol (AcF). The exogenous treatment of wild-type Arabidopsis plants with sugars showed the same transcript characteristics, indicating that sugars act as a signal for branching. We also found that the reductions induced in BRC1 expression levels in wild-type plants by the sugar treatments were suppressed in the knockout mutant of sugar transporter 1 (stp1-1).

The basic helix-loop-helix transcription factor, bHLH11 functions in the iron-uptake system in Arabidopsis thaliana.

Iron (Fe) is a micronutrient that is essential for plant development and growth. Basic helix-loop-helix (bHLH) transcription factors are a superfamily of transcription factors that are important regulatory components in transcriptional networks in plants. bHLH transcription factors have been divided into subclasses based on their amino acid sequences and domain structures.

Clade Ib basic helix-loop-helix transcription factor, bHLH101, acts as a regulatory component in photo-oxidative stress responses.

The accumulation of reactive oxygen species (ROS) leads to oxidative damage; however, ROS also acts as signaling molecules. We previously demonstrated that the inducible silencing of thylakoid membrane-bound ascorbate peroxidase Arabidopsis plants (IS-tAPX) accumulated HO in their chloroplasts, resulting in the clarification of ROS-responsive genes. In IS-tAPX plants, the transcript levels of the basic helix-loop-helix (bHLH) transcription factor bHLH101, which belongs to clade Ib bHLH, were down-regulated.

Enhancements in sucrose biosynthesis capacity affect shoot branching in Arabidopsis.

We previously demonstrated that transgenic tobacco plants expressing cyanobacterial fructose-1,6-/sedoheptulose-1,7-bisphosphatase in the cytosol increased the number of lateral shoots and leaves at elevated CO levels. These findings suggest that alterations in carbon partitioning affect the development of shoot branching. In order to elucidate the underlying mechanisms at the molecular level, we generated transgenic Arabidopsis plants overexpressing cyanobacterial fructose-1,6-bisphosphatase-II in the cytosol (AcF).

Enhanced photosynthetic capacity increases nitrogen metabolism through the coordinated regulation of carbon and nitrogen assimilation in Arabidopsis thaliana.

Plant growth and productivity depend on interactions between the metabolism of carbon and nitrogen. The sensing ability of internal carbon and nitrogen metabolites (the C/N balance) enables plants to regulate metabolism and development. In order to investigate the effects of an enhanced photosynthetic capacity on the metabolism of carbon and nitrogen in photosynthetically active tissus (source leaves), we herein generated transgenic Arabidopsis thaliana plants (ApFS) that expressed cyanobacterial fructose-1,6-/sedoheptulose-1,7-bisphosphatase in their chloroplasts.

Wax Ester Fermentation and Its Application for Biofuel Production.

In Euglena cells under anaerobic conditions, paramylon, the storage polysaccharide, is promptly degraded and converted to wax esters. The wax esters synthesized are composed of saturated fatty acids and alcohols with chain lengths of 10-18, and the major constituents are myristic acid and myristyl alcohol. Since the anaerobic cells gain ATP through the conversion of paramylon to wax esters, the phenomenon is named "wax ester fermentation".

Diverse strategies of O usage for preventing photo-oxidative damage under CO limitation during algal photosynthesis.

Photosynthesis produces chemical energy from photon energy in the photosynthetic electron transport and assimilates CO using the chemical energy. Thus, CO limitation causes an accumulation of excess energy, resulting in reactive oxygen species (ROS) which can cause oxidative damage to cells. O can be used as an alternative energy sink when oxygenic phototrophs are exposed to high light.

Arabidopsis dehydroascorbate reductase 1 and 2 modulate redox states of ascorbate-glutathione cycle in the cytosol in response to photooxidative stress.

Ascorbate and glutathione are indispensable cellular redox buffers and allow plants to acclimate stressful conditions. Arabidopsis contains three functional dehydroascorbate reductases (DHAR1-3), which catalyzes the conversion of dehydroascorbate into its reduced form using glutathione as a reductant. We herein attempted to elucidate the physiological role in DHAR1 and DHAR2 in stress responses.

Suppression of Chloroplastic Alkenal/One Oxidoreductase Represses the Carbon Catabolic Pathway in Arabidopsis Leaves during Night.

Lipid-derived reactive carbonyl species (RCS) possess electrophilic moieties and cause oxidative stress by reacting with cellular components. Arabidopsis (Arabidopsis thaliana) has a chloroplast-localized alkenal/one oxidoreductase (AtAOR) for the detoxification of lipid-derived RCS, especially α,β-unsaturated carbonyls. In this study, we aimed to evaluate the physiological importance of AtAOR and analyzed AtAOR (aor) mutants, including a transfer DNA knockout, aor (T-DNA), and RNA interference knockdown, aor (RNAi), lines.

Identification and characterization of cytosolic fructose-1,6-bisphosphatase in Euglena gracilis.

Euglena gracilis has the ability to accumulate a storage polysaccharide, a β-1,3-glucan known as paramylon, under aerobic conditions. Under anaerobic conditions, E. gracilis cells degrade paramylon and synthesize wax esters.

Enhancement of photosynthetic capacity in Euglena gracilis by expression of cyanobacterial fructose-1,6-/sedoheptulose-1,7-bisphosphatase leads to increases in biomass and wax ester production.

Background: Microalgae have recently been attracting attention as a potential platform for the production of biofuels. Euglena gracilis, a unicellular phytoflagellate, has been proposed as an attractive feedstock to produce biodiesel because it can produce large amounts of wax esters, consisting of medium-chain fatty acids and alcohols with 14:0 carbon chains. E.

Identification and characterization of Arabidopsis AtNUDX9 as a GDP-d-mannose pyrophosphohydrolase: its involvement in root growth inhibition in response to ammonium.

GDP-d-mannose (GDP-d-Man) is an important intermediate in ascorbic acid (AsA) synthesis, cell wall synthesis, protein N-glycosylation, and glycosylphosphatidylinositol-anchoring in plants. Thus, the modulation of intracellular levels of GDP-d-Man could be important for maintaining various cellular processes. Here an Arabidopsis GDP-d-Man pyrophosphohydrolase, AtNUDX9 (AtNUDT9; At3g46200), which hydrolysed GDP-d-Man to GMP and mannose 1-phosphate, was identified.

The sweet potato RbcS gene (IbRbcS1) promoter confers high-level and green tissue-specific expression of the GUS reporter gene in transgenic Arabidopsis.

Sweet potato is an important crop because of its high yield and biomass production. We herein investigated the potential of the promoter activity of a small subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase (RbcS) from sweet potato (Ipomoea batatas) in order to develop the high expression system of exogenous DNA in Arabidopsis. We isolated two different cDNAs (IbRbcS1 and IbRbcS2) encoding RbcS from sweet potato.

Characterization and physiological role of two types of chloroplastic fructose-1,6-bisphosphatases in Euglena gracilis.

The chloroplastic fructose-1,6-bisphosphatase (FBPase) is a late-limiting enzyme in the Calvin cycle. In the present study, we isolated and characterized the cDNAs encoding two types of chloroplastic FBPase isoforms (EgFBPaseI and II) from Euglena gracilis. The Km values of recombinant EgFBPaseI and EgFBPaseII for fructose 1,6-bisphosphate (Fru 1,6-P2) were 165 ± 17 and 2200 ± 200 μM, respectively.

Diversity of regulatory mechanisms of photosynthetic carbon metabolism in plants and algae.

To clarify the regulatory mechanisms of the Calvin cycle in algae, we analyzed the molecular properties of the enzymes involved in this cycle. We demonstrated that these enzymes were not regulated by redox modulation through the ferredoxin/thioredoxin system under light/dark conditions and were not sensitive to treatments with hydrogen peroxide in vitro, unlike the chloroplastic thiol-modulated enzymes of plants. On the other hand, we found that cyanobacteria possessed a unique enzyme involved in the Calvin cycle.

A gain-of-function mutation of plastidic invertase alters nuclear gene expression with sucrose treatment partially via GENOMES UNCOUPLED1-mediated signaling.

Plastid gene expression (PGE) is one of the signals that regulate the expression of photosynthesis-associated nuclear genes (PhANGs) via GENOMES UNCOUPLED1 (GUN1)-dependent retrograde signaling. We recently isolated Arabidopsis sugar-inducible cotyledon yellow-192 (sicy-192), a gain-of-function mutant of plastidic invertase, and showed that following the treatment of this mutant with sucrose, the expression of PhANGs as well as PGE decreased, suggesting that the sicy-192 mutation activates a PGE-evoked and GUN1-mediated retrograde pathway. To clarify the relationship between the sicy-192 mutation, PGE, and GUN1-mediated pathway, plastid and nuclear gene expression in a double mutant of sicy-192 and gun1-101, a null mutant of GUN1 was studied.

Transcriptional control of vitamin C defective 2 and tocopherol cyclase genes by light and plastid-derived signals: the partial involvement of GENOMES UNCOUPLED 1.

Previous findings have suggested that light and plastid-derived signals are involved in the regulation of biosynthetic pathways for l-ascorbic acid (AsA) and tocopherols (Toc). Photosynthetic electron transport (PET) activity, plastid gene expression (PGE), and the tetrapyrrole metabolism have been identified as signals that regulate nuclear gene expression through the GENOMES UNCOUPLED 1 (GUN1) protein. Here, we examined the effects of disrupting GUN1 on these pathways.

Crystal structure of the catalase-peroxidase KatG W78F mutant from Synechococcus elongatus PCC7942 in complex with the antitubercular pro-drug isoniazid.

Isoniazid (INH) is a pro-drug that has been extensively used to treat tuberculosis. INH is activated by the heme enzyme catalase-peroxidase (KatG), but the mechanism of the activation is poorly understood, in part because the INH binding site has not been clearly established. Here, we observed that a single-residue mutation of KatG from Synechococcus elongatus PCC7942 (SeKatG), W78F, enhances INH activation.

O2-dependent large electron flow functioned as an electron sink, replacing the steady-state electron flux in photosynthesis in the cyanobacterium Synechocystis sp. PCC 6803, but not in the cyanobacterium Synechococcus sp. PCC 7942.

To determine whether alternative electron flow (AEF) can replace the photosynthetic electron flow in cyanobacteria, we used an open O2-electrode system to monitor O2-exchange over a long period. In air-grown Synechocystis sp. PCC 6803 (S.

The 2.2 Å resolution structure of the catalase-peroxidase KatG from Synechococcus elongatus PCC7942.

The crystal structure of catalase-peroxidase from Synechococcus elongatus PCC7942 (SeKatG) was solved by molecular replacement and refined to an Rwork of 16.8% and an Rfree of 20.6% at 2.

Ferulic acid 5-hydroxylase 1 is essential for expression of anthocyanin biosynthesis-associated genes and anthocyanin accumulation under photooxidative stress in Arabidopsis.

Anthocyanins are important for preventing photoinhibition and photodamage. By comprehensive reverse genetic analysis of chloroplast-produced H2O2-responsive genes, we isolated here an anthocyanin-deficient mutant under photooxidative stress, which lacked ferulate 5-hydroxylase 1 (FAH1) involved in the phenylpropanoid pathway. Interestingly, the expression of anthocyanin biosynthesis-associated genes was also inhibited in this mutant.

Activation of γ-aminobutyrate production by chloroplastic H(2)O(2) is associated with the oxidative stress response.

We isolated an Arabidopsis knockout line lacking glutamate decarboxylase 1 (GAD1), one that produced γ-aminobutyrate (GABA), as an oxidative stress-insensitive mutant, and found that chloroplastic H(2)O(2) enhances GAD1 expression and GABA levels. This suggests a possible relationship between GABA metabolism and the chloroplastic H(2)O(2)-mediated stress response.