Explore the vast range of titles available.

OsTZF1 is a member of the CCCH-type zinc finger gene family in rice (Oryza sativa). Expression of OsTZF1 was induced by drought, high-salt stress, and hydrogen peroxide. OsTZF1 gene expression was also induced by abscisic acid, methyl jasmonate, and salicylic acid. Histochemical activity of β-glucuronidase in transgenic rice plants containing the promoter of OsTZF1 fused with β-glucuronidase was observed in callus, coleoptile, young leaf, and panicle tissues. Upon stress, OsTZF1-green fluorescent protein localization was observed in the cytoplasm and cytoplasmic foci. Transgenic rice plants overexpressing OsTZF1 driven by a maize (Zea mays) ubiquitin promoter (Ubi:OsTZF1-OX [for overexpression]) exhibited delayed seed germination, growth retardation at the seedling stage, and delayed leaf senescence. RNA interference (RNAi) knocked-down plants (OsTZF1-RNAi) showed early seed germination, enhanced seedling growth, and early leaf senescence compared with controls. Ubi:OsTZF1-OX plants showed improved tolerance to high-salt and drought stresses and vice versa for OsTZF1-RNAi plants. Microarray analysis revealed that genes related to stress, reactive oxygen species homeostasis, and metal homeostasis were regulated in the Ubi:OsTZF1-OX plants. RNA-binding assays indicated that OsTZF1 binds to U-rich regions in the 3' untranslated region of messenger RNAs, suggesting that OsTZF1 might be associated with RNA metabolism of stress-responsive genes. OsTZF1 may serve as a useful biotechnological tool for the improvement of stress tolerance in various plants through the control of RNA metabolism of stress-responsive genes.

High temperature effects attributable to climate change can affect rice quality. The chalky area of rice grains is often used to evaluate of rice grain starch quality, but the overall effect of high temperatures on grain chalkiness and overall nutrient quality has not been fully clarified. Thus, in this study, we assessed high temperature effects on grain weight, chalkiness, and nutrient contents. Rice grains were classified into four groups on the basis of the chalky area in scanned grain images: P (0%), S (0–15%), M (15–40%), and L (≥40%). Then, the amylose, protein and mineral nutrient concentrations were assessed in each chalkiness classification. High temperatures during grain filling markedly decreased the grain weight and the amylose content of milled rice but increased the chalky area of the grains as well as protein content and the concentrations of most minerals. There were significant negative correlations between mineral contents and both grain weights and amylose contents of milled rice. These results indicate that increases in grain chalky areas due to high temperatures during grain filling also increase grain mineral contents.

Osmotic adjustment plays a fundamental role in water stress responses and growth in plants; however, the molecular mechanisms governing this process are not fully understood. Here, we demonstrated that the KUP potassium transporter family plays important roles in this process, under the control of abscisic acid (ABA) and auxin. We generated Arabidopsis thaliana multiple mutants for K⁺ uptake transporter 6 (KUP6), KUP8, KUP2/SHORT HYPOCOTYL3, and an ABA-responsive potassium efflux channel, guard cell outward rectifying K⁺ channel (GORK). The triple mutants, kup268 and kup68 gork, exhibited enhanced cell expansion, suggesting that these KUPs negatively regulate turgor-dependent growth. Potassium uptake experiments using ⁸⁶radioactive rubidium ion (⁸⁶Rb⁺) in the mutants indicated that these KUPs might be involved in potassium efflux in Arabidopsis roots. The mutants showed increased auxin responses and decreased sensitivity to an auxin inhibitor (1-N-naphthylphthalamic acid) and ABA in lateral root growth. During water deficit stress, kup68 gork impaired ABAmediated stomatal closing, and kup268 and kup68 gork decreased survival of drought stress. The protein kinase SNF1-related protein kinases 2E (SRK2E), a key component of ABA signaling, interacted with and phosphorylated KUP6, suggesting that KUP functions are regulated directly via an ABA signaling complex. We propose that the KUP6 subfamily transporters act as key factors in osmotic adjustment by balancing potassium homeostasis in cell growth and drought stress responses.

Two free flavin-independent enzymes were purified by detecting the NAD(P)H oxidation in the presence of Fe(III)-EDTA and t-butyl hydroperoxide from E. coli. The enzyme that requires NADH or NADPH as an electron donor was a 28 kDa protein, and N-terminal sequencing revealed it to be oxygen-insensitive nitroreductase (NfnB). The second enzyme that requires NADPH as an electron donor was a 30 kDa protein, and N-terminal sequencing revealed it to be ferredoxin-NADP⁺ reductase (Fpr). The chemical stoichiometry of the Fenton activities of both NfnB and Fpr in the presence of Fe(III)-EDTA, NAD(P)H and hydrogen peroxide was investigated. Both enzymes showed a one-electron reduction in the reaction forming hydroxyl radical from hydrogen peroxide. Also, the observed Fenton activities of both enzymes in the presence of synthetic chelate iron compounds were higher than their activities in the presence of natural chelate iron compounds. When the Fenton reaction occurs, the ferric iron must be reduced to ferrous iron. The ferric reductase activities of both NfnB and Fpr occurred with synthetic chelate iron compounds. Unlike NfnB, Fpr also showed the ferric reductase activity on an iron storage protein, ferritin, and various natural iron chelate compounds including siderophore. The Fenton and ferric reductase reactions of both NfnB and Fpr occurred in the absence of free flavin. Although the k cat/K m value of NfnB for Fe(III)-EDTA was not affected by free flavin, the k cat/K m value of Fpr for Fe(III)-EDTA was 12-times greater in the presence of free FAD than in the absence of free FAD.

We purified free flavin-independent NADPH oxidoreductase from Synechocystis sp. PCC6803 based on NADPH oxidation activity elicited during reduction of t-butyl hydroperoxide in the presence of Fe(III)-EDTA. The N-terminal sequencing of the purified enzyme revealed it to be ferredoxin-NADP⁺ oxidoreductase (FNR S ). The purified enzyme reacted with cytochrome c, ferricyanide and 2,6-dichloroindophenol (DCIP). The substrate specificity of the enzyme was similar to the known FNR. DNA degradation occurring in the presence of NADPH, Fe(III)-EDTA and hydrogen peroxide was potently enhanced by the purified enzyme, indicating that Synechocystis FNR S may drive the Fenton reaction. The Fenton reaction by Synechocystis FNR S in the presence of natural chelate iron compounds tended to be considerably lower than that in the presence of synthetic chelate iron compounds. The Synechocystis FNR S is considered to reduce ferric iron to ferrous iron when it evokes the Fenton reaction. Although Synechocystis FNR S was able to reduce iron compounds in the absence of free flavin, the ferric reduction by the enzyme was enhanced by the addition of free flavin. The enhancement was detected not only in the presence of natural chelate iron compounds but also synthetic chelate iron compounds.

The photosynthetic bacterium Rhodobacter sphaeroides (R. sphaeroides) f. sp. denitrificans IL106 accumulates trehalose as the major organic osmoprotectant in response to a salt stress. An analysis of the R. sphaeroides 2.4.1 genome sequence revealed the presence of five different genes encoding enzymes belonging to three putative trehalose biosynthesis pathways (OtsA-OtsB, TreY-TreZ, and TreS). The function of the different pathways of trehalose was studied by characterizing strains defective in individual trehalose biosynthetic routes. A phenotypic comparison revealed that trehalose synthesis in R. sphaeroides f. sp. denitrificans IL106 is mediated mainly by the OtsA-OtsB pathway and, to some extent, by the TreY-TreZ pathway. Strains with the simultaneous inactivation of these two pathways were completely unable to synthesize trehalose. On the other hand, treS mutants showed an increase in the trehalose level. These results suggest that treS plays a role in trehalose degradation. In addition, treS was found to be important in reducing trehalose after osmotic stress was removed. In this report, we show that the strains that accumulate the most trehalose adapt to salt stress earlier. This is the first report of an organism using multiple pathways to synthesize trehalose solely for use as a compatible solute against salt stress.

The purpose of this study is to confirm whether T2-weighted imaging and perfusion imaging, i.e. autoradiogram of^sup 14^C-iodoantipyrine, on the course of brain edema correspond to each other or not. Cold injured rat brains were used as a model and were sequentially examined by both methods and compared with each other and with histological specimens. Special focus relies on the time changes in the lesions. High SI of T2-weighted images were observed and the percentages in the high SI area to the total brain area in the same slice were 4.7±0.31, 5.6±0.46 and 3.4±0.42 for 6,24 and 48 hours, respectively. By contrast, low perfusion areas were indicated in the perfusion study and their percentages were 4.6±0.55, 5.6±0.86 and 2.4±0.35 for 6,24 and 48 hours, respectively. At 48 hours after cold injury, low perfusion areas were smaller than high SI areas. Moreover, high accumulation areas consisting of macrophages were observed surrounding necrosis. It is concluded that there is dissociation between perfusion and T2-weighted MR imaging, where the collection of macrophages surrounding edema lesions and necrosis had the same appearance on MRI and different accumulations on perfusion studies.[PUBLICATION ABSTRACT]

We purified free flavin-independent NADPH oxidoreductase from Synechocystis sp. PCC6803 based on NADPH oxidation activity elicited during reduction of t-butyl hydroperoxide in the presence of Fe(III)-EDTA. The N-terminal sequencing of the purified enzyme revealed it to be ferredoxin-NADP super(+) oxidoreductase (FNR sub( S )). The purified enzyme reacted with cytochrome c, ferricyanide and 2,6-dichloroindophenol (DCIP). The substrate specificity of the enzyme was similar to the known FNR. DNA degradation occurring in the presence of NADPH, Fe(III)-EDTA and hydrogen peroxide was potently enhanced by the purified enzyme, indicating that Synechocystis FNR sub( S ) may drive the Fenton reaction. The Fenton reaction by Synechocystis FNR sub( S ) in the presence of natural chelate iron compounds tended to be considerably lower than that in the presence of synthetic chelate iron compounds. The Synechocystis FNR sub( S ) is considered to reduce ferric iron to ferrous iron when it evokes the Fenton reaction. Although Synechocystis FNR sub( S ) was able to reduce iron compounds in the absence of free flavin, the ferric reduction by the enzyme was enhanced by the addition of free flavin. The enhancement was detected not only in the presence of natural chelate iron compounds but also synthetic chelate iron compounds.

We purified free flavin-independent NADPH oxidoreductase from Synechocystis sp. PCC6803 based on NADPH oxidation activity elicited during reduction of t-butyl hydroperoxide in the presence of Fe(III)-EDTA. The N-terminal sequencing of the purified enzyme revealed it to be ferredoxin-NADP^sup +^ oxidoreductase (FNR^sub S^). The purified enzyme reacted with cytochrome c, ferricyanide and 2,6-dichloroindophenol (DCIP). The substrate specificity of the enzyme was similar to the known FNR. DNA degradation occurring in the presence of NADPH, Fe(III)-EDTA and hydrogen peroxide was potently enhanced by the purified enzyme, indicating that Synechocystis FNR^sub S^ may drive the Fenton reaction. The Fenton reaction by Synechocystis FNR^sub S^ in the presence of natural chelate iron compounds tended to be considerably lower than that in the presence of synthetic chelate iron compounds. The Synechocystis FNR^sub S^ is considered to reduce ferric iron to ferrous iron when it evokes the Fenton reaction. Although Synechocystis FNR^sub S^ was able to reduce iron compounds in the absence of free flavin, the ferric reduction by the enzyme was enhanced by the addition of free flavin. The enhancement was detected not only in the presence of natural chelate iron compounds but also synthetic chelate iron compounds.[PUBLICATION ABSTRACT]

Two free flavin-independent enzymes were purified by detecting the NAD(P)H oxidation in the presence of Fe(III)-EDTA and t-butyl hydroperoxide from E. coli. The enzyme that requires NADH or NADPH as an electron donor was a 28kDa protein, and N-terminal sequencing revealed it to be oxygen-insensitive nitroreductase (NfnB). The second enzyme that requires NADPH as an electron donor was a 30kDa protein, and N-terminal sequencing revealed it to be ferredoxin-NADP super(+) reductase (Fpr). The chemical stoichiometry of the Fenton activities of both NfnB and Fpr in the presence of Fe(III)-EDTA, NAD(P)H and hydrogen peroxide was investigated. Both enzymes showed a one-electron reduction in the reaction forming hydroxyl radical from hydrogen peroxide. Also, the observed Fenton activities of both enzymes in the presence of synthetic chelate iron compounds were higher than their activities in the presence of natural chelate iron compounds. When the Fenton reaction occurs, the ferric iron must be reduced to ferrous iron. The ferric reductase activities of both NfnB and Fpr occurred with synthetic chelate iron compounds. Unlike NfnB, Fpr also showed the ferric reductase activity on an iron storage protein, ferritin, and various natural iron chelate compounds including siderophore. The Fenton and ferric reductase reactions of both NfnB and Fpr occurred in the absence of free flavin. Although the k sub(cat)/K sub(m) value of NfnB for Fe(III)-EDTA was not affected by free flavin, the k sub(cat)/K sub(m) value of Fpr for Fe(III)-EDTA was 12-times greater in the presence of free FAD than in the absence of free FAD.