ERECTA is required for protection against heat-stress in the AS1/ AS2 pathway to regulate adaxial-abaxial leaf polarity in Arabidopsis

In seed plants, formation of the adaxial–abaxial polarity is of primary importance in leaf patterning. Since Arabidopsis thaliana (L.) Heynh. genes ASYMMETRIC LEAVES1 (AS1) and ASYMMETRIC LEAVES2 (AS2) are key regulators in specifying adaxial leaf identity, and ERECTA is involved in the AS1/AS2 pathway for regulating adaxial–abaxial polarity [L. Xu et al. (2003) Development 130:4097–4107], we studied the physiological functions of the ERECTA protein in plant development. We analyzed the effects of different environmental conditions on a special leaf structure in the as1 and as2 mutants. This structure, called the lotus-leaf, reflects a severe loss of adaxial–abaxial polarity in leaves. Higher concentrations of salt or other osmotic substance and lower temperature severely affected plant growth both in the wild type and the mutants, but did not affect lotus-leaf frequency in the as1 and as2 mutants. as1 and as2 mutants exhibited a very low lotus-leaf frequency at 22°C, a temperature that favors Arabidopsis growth. The lotus-leaf frequency rose significantly with an increase in growth temperature, and only in plants that are in the erecta mutation background. These results suggest that ERECTA function is required for reducing plant sensitivity to heat stress during adaxial–abaxial polarity formation in leaves.Abbreviations AS1, AS2 ASYMMETRIC LEAVES1, 2 - ER ERECTA     

The petunia homologue of the Antirrhinum majus candi and Zea mays A2 flavonoid genes; homology to flavanone 3-hydroxylase and ethylene-forming enzyme

The synthesis of anthocyanins in higher plants involves many enzymatic steps. Here we describe the isolation and characterization of a cDNA, ant17, which encodes a protein that has 73% amino acid sequence identity with the candi gene product of Antirrhinum majus and 48% with that of the maize a2 gene. This protein may therefore be involved in the synthesis of anthocyanins in the steps after the action of dihydroflavonol 4-reductase. This is consistent with the absence of ant17 expression in the regulatory anthocyanin mutants of petunia an1, an2 and an11. Furthermore, ant17 is predominantly expressed in corollas and anthers and is induced by gibberellic acid.     

CHB2, a member of the SWI3 gene family,is a global regulator in Arabidopsis

The SWI/SNF complex is an ATP-dependent chromatin remodeling complex that plays an important role in the regulation of eukaryotic gene expression. Very little is known about the function of SWI/SNF complex in plants compared with animals and yeast. SWI3 is one of the core components of the SWI/SNF chromatin remodeling complexes in yeast. We have identified a putative SWI3-like cDNA clone, CHB2 (AtSWI3B), from Arabidopsis thaliana by screening the expressed sequence tag database. CHB2 encodes a putative protein of 469 amino acids and shares 23% amino acid sequence identity and 64% similarity with the yeast SWI3. The Arabidopsis genome contains four SWI3-like genes, namely CHB1 (AtSWI3A), CHB2 (AtSWI3B), CHB3 (AtSWI3C) and CHB4 (AtSWI3D). The expression of CHB2, CHB3 and CHB4 mRNA was detected in all tissues analyzed by RT-PCR. The expression of CHB1 mRNA, however, could not be detected in the siliques, suggesting that there is differential expression among CHB genes in different Arabidopsis tissues. To investigate the role of CHB2 in plants, Arabidopsis plants were transformed with a gene construct comprising a CHB2 cDNA in the antisense orientation driven by the CaMV 35S promoter. Repression of CHB2 expression resulted in pleiotropic developmental abnormalities including abnormal seedling and leaf phenotypes, dwarfism, delayed flowering and no apical dominance, suggesting a global role for CHB2 in the regulation of gene expression. Our results indicate that CHB2 plays an essential role in plant growth and development.     

Role of Neostriatal Dopamine D1 and D2 Receptors in the Organization of Neuronal Activity in the Entopeduncular Nucleus

In chronic experiments on cats, we studied the effects of selective blockade of the dopamine D1 and D2 receptors in the nucleus caudatus (NC) against the background neuronal activity (BA) in the entopeduncular nucleus (ENT) and on the responses of these neurons evoked by stimulation of the subthalamic nucleus (STN). A blocker of D1 receptors, SCH 23390, and sulpiride, a blocker of D2 receptors, when injected into the NC head, led to changes in the BA frequency. The direction of these effects was different: blockade of the D2 receptors evoked a significant decrease in the BA frequency of ENT neurons, but when the D2 receptors were blocked, a trend toward an increase in this frequency was observed. Some of the ENT cells demonstrated similar changes in the temporal organization of their impulse activity with blockade of the D1 and D2 receptors. Namely, besides single action potentials (AP), high-frequency burst discharges began to be generated. Blockade of both D1 and D2 receptors prolonged the responses of ENT neurons to STN stimulation due to the appearance of similar AP bursts, while control animals demonstrated reactions consisting of solely single AP. The question on a dual (synergic and antagonistic) involvement of the neostriatal D1 and D2 receptors in the dopaminergic regulation of the basal ganglia is under discussion.     

Redirection of biochemical pathways for the enhancement of H2 production by Enterobacter cloacae

Improvement in H₂ production was achieved through redirection of metabolic pathways by blocking formation of alcohol and some organic acids in Enterobacter cloacae IIT-BT 08. The wild type strain was more susceptible to allyl alcohol (7 mM) and to the combined effect of NaBr and NaBrO₃ (40 mM each at pH 5.5) than were double mutants, with defects in both alcohol and organic acid formation pathways, which had higher H₂ yields (3.4 mol mol^–1 glucose) than the wild type strain (2.1 mol mol^–1 glucose).     

塔里木河下游胡杨群落CO2通量特征与水分利用效率

以极端干旱环境中的胡杨群落为研究对象,利用涡度相关通量观测系统,研究了胡杨群落CO_2通量与水分利用效率在不同物候期的动态规律。结果表明:胡杨CO_2通量在不同物候期日变化趋势基本一致,但存在明显的季节差异,其中果熟期CO_2通量变化幅度最大,开花期最小,展叶期介于二者之间。相关分析表明,胡杨群落CO_2通量均与显热通量、潜热通量、动量通量、土壤热通量、净辐射以及空气相对湿度呈极显著相关。其中,净辐射、潜热通量和显热通量与CO_2通量的相关系数较大,其变化范围分别为-0.82—-0.88、-0.64—-0.66和-0.63—-0.94,是影响群落CO_2通量的最主要环境因子。胡杨群落水分利用效率(WUE)同样存在明显日变化规律。其时间动态表现为:群落水分利用效率在开花期、叶黄期和落叶期变化幅度大,开花期最高,在展叶期和果熟期WUE最稳定。净辐射和风速是影响群落水分利用效率的两个最关键要素。     

A locus controlling the activity of UDP-galactose:GM2(NeuGc) galactosyltransferase in mouse liver is linked to the H-2 complex

Genetic polymorphism in the expression of the G_M1(NeuGc) ganglioside has been shown in the liver of inbred strains of mice. Through analysis of the gangliosides of H-2 congenic and recombinant strains, this polymorphism was demonstrated to be controlled by a locus mapped left outside of the H-2 complex on chromosome 17, and the locus was assumed to control the level of the activity of G_M1(NeuGc) synthetase, UDP-galactose:G_M2(NeuGc) galactosyltransferase (E.C.2.4.1.62) [Hashimotoet al., J Biochem (1983) 94:2049-54].In the present study we analyzed the genetic linkage between the activity of the galactosyltransferase and the H-2 haplotype. For this purpose, we selected two inbred strains of mice, WHT/Ht and BALB/c, because they have different levels of the transferase activity and show different H-2 haplotypes; the specific activity of the transferase obtained with BALB/c was one-eighth of that with WHT/Ht, and BALB/c expressed the la.7 antigen as one of the products encoded in their H-2^d complex, whereas WHT/Ht did not. To analyze the linkage between these two phenotypes, WHT/Ht were mated with BALB/c to obtain the F₁ mice, and the female F₁ mice were then backcrossed to WHT/Ht. It was found that one half of the backcross generation expressed the la.7 antigen derived from BALB/c and had a significantly lower specific activity of the transferase than that of WHT/Ht, while the other half did not express the la.7 antigen but had the same specific activity of the transferase as that obtained with WHT/Ht.These results suggest that the locus controlling the level of the transferase activity in mouse liver is linked to the H-2 complex on chromosome 17.Abbreviations NeuGc N-glycolylneuraminic acid The ganglioside nomenclature is based on the system of Svennerholm, J Neurochem (1963) 10:613-23. The sialic acid species present is shown in parentheses after the ganglioside abbreviation.     

The roles of amino acid residues at positions 216 and 219 in the structural stability and metabolic functions of rat cytochrome P450 2D1 and 2D2

We examined the effects of the mutual substitution of amino acid residues at positions 216 and 219 between rat CYP2D1 and CYP2D2 on their microsomal contents and enzymatic functions using a yeast cell expression system and 5-methoxy-N,N-diisopropyltryptamine (5-MeO-DIPT) as a substrate. CYP2D1 has amino acid residues, leucine and valine, at positions of 216 and 219, respectively, whereas CYP2D2 has phenylalanine and aspartic acid at the same positions. In reduced carbon monoxide-difference spectroscopic analysis, the substitution of Asp-219 of CYP2D2 by valine markedly increased a peak at 450 nm and concomitantly decreased a peak at 420 nm, while the replacement of Phe-216 of CYP2D2 with leucine gave no observable change. The double substitution of Phe-216 and Asp-219 by leucine and valine, respectively, yielded a typical CYP spectrum. The substitution of Val-219 of CYP2D1 by aspartic acid decreased the CYP content to one-half, whereas the replacement of Leu-216 with phenylalanine did not have any effect. The double substitution of Leu-216 and Val-219 of CYP2D1 by phenylalanine and aspartic acid, respectively, diminished the CYP content by 90%. CYP2D1 catalyzed both 5-MeO-DIPT N-deisopropylation and O-demethylation at relatively low levels, while CYP2D2 catalyzed 5-MeO-DIPT O-demethylation efficiently. The substitution of the amino acid at position 216 substantially increased 5-MeO-DIPT oxidation activities of the two CYP2D enzymes. The replacement of the amino acid at position 219 increased the 5-MeO-DIPT O- and N-dealkylation activities of CYP2D1, whereas it decreased the 5-MeO-DIPT O-demethylation activity of CYP2D2. These results indicate that amino acid residues at positions 216 and 219 have important roles in the enzymatic functions of rat CYP2D1 and CYP2D2.     

Atrazine resistance in the grass Poa annua is due to a single base change in the chloroplast gene for the D1 protein of photosystem II

Summary We report here the first molecular characterization of maternally inherited atrazine resistance in a monocot. As has been found in dicots, resistance in the grass Poa annua is correlated with a decrease in the ability of herbicides to bind to thylakoids and with an alteration in the gene for the D1 protein of photosystem II which would result in a change from a serine to an alanine residue at position 264 of the protein. Azidoatrazine, a photoaffinity-labelled analogue of atrazine, binds to the putative product of this gene in sensitive but not resistant biotypes of P. annua. The wheat gene and protein are shown to resemble those of the atrazine-sensitive P. annua biotype.Now Institute of Plant Science Research (Cambridge Laboratory)     

Vitamin D and metabolic health with special reference to the effect of vitamin D on serum lipids

Considering that the vitamin D receptor as well as the 1-α-hydroxylase enzyme that converts 25-hydroxyvitamin D (25(OH)D) to its active form 1,25-dihydroxyvitamin D have been found in tissues throughout the body, it is likely that vitamin D is important for more than the calcium balance. Accordingly, low serum levels of 25(OH)D have been associated with mortality, cardiovascular disease, type 2 diabetes, hypertension and obesity. Low serum levels of 25(OH)D have also been associated with an unfavourable lipid profile, which could possible explain the relation with cardiovascular disease and mortality. However, the relation between vitamin D and lipids have so far received little attention and is therefore the main focus of the present review. A PubMed search identified 22 cross-sectional studies where serum levels of 25(OH)D and lipids were related and that included a minimum of 500 subjects, and 10 placebo-controlled double-blind intervention studies with vitamin D where more than 50 subjects were included. In all the cross-sectional studies serum 25(OH)D was positively associated with high-density lipoprotein cholesterol (HDL-C) resulting in a favourable low-density lipoprotein cholesterol (LDL-C) (or total cholesterol) to HDL-C ratio. There was also a uniform agreement between studies on a negative relation between serum 25(OH)D and triglycerides (TG). On the other hand, the intervention studies gave divergent results, with some showing a positive and some a negative effect of vitamin D supplementation. However, none of the intervention studies were specifically designed for evaluating the relation between vitamin D and lipids, none had hyperlipemia as an inclusion criterion, and none were sufficiently powered. In only one study was a significant effect seen with an 8% (0.28 mmol/L) increase in serum LDL-C and a 16% (0.22 mmol/L) decrease in serum TG in those given vitamin D as compared to the placebo group. Accordingly, the effect of vitamin D supplementation on serum lipids is at present uncertain. Considering the numerous other promising vitamins and minerals that when properly tested have been disappointing, one should wait for the results of forthcoming vitamin D intervention studies before drawing conclusions on potential beneficial effects of vitamin D.     

Genome-scale reconstruction and <Emphasis Type="Italic">in silico</Emphasis> analysis of the <Emphasis Type="Italic">Clostridium acetobutylicum</Emphasis> ATCC 824 metabolic network

To understand the metabolic characteristics of Clostridium acetobutylicum and to examine the potential for enhanced butanol production, we reconstructed the genome-scale metabolic network from its annotated genomic sequence and analyzed strategies to improve its butanol production. The generated reconstructed network consists of 502 reactions and 479 metabolites and was used as the basis for an in silico model that could compute metabolic and growth performance for comparison with fermentation data. The in silico model successfully predicted metabolic fluxes during the acidogenic phase using classical flux balance analysis. Nonlinear programming was used to predict metabolic fluxes during the solventogenic phase. In addition, essential genes were predicted via single gene deletion studies. This genome-scale in silico metabolic model of C. acetobutylicum should be useful for genome-wide metabolic analysis as well as strain development for improving production of biochemicals, including butanol. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users. J. L. and H. Y. equally contributed to this work.     

Differential regulation of the ascorbic acid transporter SVCT2 during development and in response to ascorbic acid depletion

The sodium-dependent vitamin C transporter-2 (SVCT2) is the only ascorbic acid (ASC) transporter significantly expressed in brain. It is required for life and is critical during brain development to supply adequate levels of ASC. To assess SVCT2 function in the developing brain, we studied time-dependent SVCT2 mRNA and protein expression in mouse brain, using liver as a comparison tissue because it is the site of ASC synthesis. We found that SVCT2 expression followed an inverse relationship with ASC levels in the developing brain. In cortex and cerebellum, ASC levels were high throughout late embryonic stages and early post-natal stages and decreased with age, whereas SVCT2 mRNA and protein levels were low in embryos and increased with age. A different response was observed for liver, in which ASC levels and SVCT2 expression were both low throughout embryogenesis and increased post-natally. To determine whether low intracellular ASC might be capable of driving SVCT2 expression, we depleted ASC by diet in adult mice unable to synthesize ASC. We observed that SVCT2 mRNA and protein were not affected by ASC depletion in brain cortex, but SVCT2 protein expression was increased by ASC depletion in the cerebellum and liver. The results suggest that expression of the SVCT2 is differentially regulated during embryonic development and in adulthood.     

The D1-173 amino acid is a structural determinant of the critical interaction between D1-Tyr161 (TyrZ) and D1-His190 in Photosystem II

The main cofactors of Photosystem II (PSII) are borne by the D1 and D2 subunits. In the thermophilic cyanobacterium Thermosynechococcus elongatus, three psbA genes encoding D1 are found in the genome. Among the 344 residues constituting the mature form of D1, there are 21 substitutions between PsbA1 and PsbA3, 31 between PsbA1 and PsbA2, and 27 between PsbA2 and PsbA3. In a previous study (Sugiura et al., J. Biol. Chem. 287 (2012), 13336-13347) we found that the oxidation kinetics and spectroscopic properties of Tyr_Z were altered in PsbA2-PSII when compared to PsbA(1/3)-PSII. The comparison of the different amino acid sequences identified the residues Cys144 and Pro173 found in PsbA1 and PsbA3, as being substituted in PsbA2 by Pro144 and Met173, and thus possible candidates accounting for the changes in the geometry and/or the environment of the Tyr_Z/His190 phenol/imidizol motif. Indeed, these amino acids are located upstream of the α-helix bearing Tyr_Z and between the two α-helices bearing Tyr_Z and its hydrogen-bonded partner, D1/His190. Here, site-directed mutants of PSII, PsbA3/Pro173Met and PsbA2/Met173Pro, were analyzed using X- and W-band EPR and UV-visible time-resolved absorption spectroscopy. The Pro173Met substitution in PsbA2-PSII versus PsbA3-PSII is shown to be the main structural determinant of the previously described functional differences between PsbA2-PSII and PsbA3-PSII. In PsbA2-PSII and PsbA3/Pro173Met-PSII, we found that the oxidation of Tyr_Z by P₆₈₀^+● was specifically slowed during the transition between S-states associated with proton release. We thus propose that the increase of the electrostatic charge of the Mn₄CaO₅ cluster in the S₂ and S₃ states could weaken the strength of the H-bond interaction between Tyr_Z^● and D1/His190 in PsbA2 versus PsbA3 and/or induce structural modification(s) of the water molecules network around Tyr_Z.     

TheCBP2 gene fromSaccharomyces douglasii is a functional homologue of theSaccharomyces cerevisiae gene and is essential for respiratory growth in the presence of a wild-type (intron-containing) mitochondrial genome

InSaccharomyces cerevisiae the only known role of theCBP2 gene is the excision of the fifth intron of the mitochondrialcyt b gene (bI5). We have cloned theCBP2 gene fromSaccharomyces douglasii (a close relative ofS. cerevisiae). A comparison of theS. douglasii andS. cerevisiae sequences shows that there are 14% nucleotide substitutions in the coding region, with transitions being three times more frequent than transversions. At the protein level sequence identity is 87%. We have demonstrated that theS. douglasii CBP2 gene is essential for respiratory growth in the presence of a wild-typeS. douglasii mitochondrial genome, but not in the presence of an intronlessS. cerevisiae mitochondrial genome. Also theS. douglasii andS. cerevisiae CBP2 genes are completely interchangeable, even though the intron bI5 is absent from theS. douglasii mitochondrial genome.     

Application of the secondary structure model of rRNA for phylogeny: D2-D3 expansion segments of the LSU gene of plant-parasitic nematodes from the family Hoplolaimidae Filipjev, 1934

Knowledge of rRNA structure is increasingly important to assist phylogenetic analysis through reconstructing optimal alignment, utilizing molecule features as an additional source of data and refining appropriate models of evolution of the molecule. We describe a procedure of optimization for alignment and a new coding method for nucleotide sequence data using secondary structure models of the D2 and D3 expansion fragments of the LSU-rRNA gene reconstructed for fifteen nematode species of the agriculturally important and diverse family Hoplolaimidae, order Tylenchida. Using secondary structure information we converted the original sequence data into twenty-eight symbol codes and submitted the transformed data to maximum parsimony analysis. We also applied the original sequence data set for Bayesian inference. This used the doublet model with sixteen states of nucleotide doublets for the stem region and the standard model of DNA substitution with four nucleotide states for loops and bulges. By this approach, we demonstrate that using structural information for phylogenetic analyses led to trees with lower resolved relationships between clades and likely eliminated some artefactual support for misinterpreted relationships, such as paraphyly of Helicotylenchus or Rotylenchus. This study as well as future phylogenetic analyses is herein supported by the development of an on-line database, NEMrRNA, for rRNA molecules in a structural format for nematodes. We also have developed a new computer program, RNAstat, for calculation of nucleotide statistics designed and proposed for phylogenetic studies.