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Tomato (Solanum lycopersicum) is one of the highest-value vegetable crops worldwide. Understanding the genetic regulation of primary metabolite levels can inform efforts aimed toward improving the nutrition of commercial tomato cultivars, while maintaining key traits such as yield and stress tolerance. We identified 388 suggestive association loci (including 126 significant loci) for 92 metabolic traits including nutrition and flavor-related loci by genome-wide association study from 302 accessions in two different environments. Among them, an ascorbate quantitative trait locus TFA9 (OMATO RUIT SCORBATEON CHROMOSOME ) co-localized with SlbHLH59, which promotes high ascorbate accumulation by directly binding to the promoter of structural genes involved in the D-mannose/L-galactose pathway. The causal mutation of TFA9 is an 8-bp InDel, named InDel_8, located in the promoter region of SlbHLH59 and spanned a 5’UTR Py-rich stretch motif affecting its expression. Phylogenetic analysis revealed that differentially expressed SlbHLH59 alleles were selected during tomato domestication. Our results provide a dramatic illustration of how ascorbate biosynthesis can be regulated and was selected during the domestication of tomato. Furthermore, the findings provide novel genetic insights into natural variation of metabolites in tomato fruit, and will promote efficient utilization of metabolite traits in tomato improvement. [ABSTRACT FROM AUTHOR]

The aim of this work was to study the toxicity of nanosheet zinc oxide nanoparticle with the size of 45 nm. The penetration of nanoparticles at an exposure by a localized spray does not make it possible to understand the mechanism of transport and bioavailability of the nanoparticles. In contrast, nanoparticles penetrated, via the roots, as a function of their diameter, the smaller ones having caused leaf stress (by translocation) at low concentrations. So that the choice of method of root application. Plants treated with 50 mg L−1 of ZnO-NPs presented disturbance in leaf due to changes in chlorophyll's biosynthesis. The highest value of the photosynthetic pigments was recorded at 5 mg L−1 of ZnO-NPs. However, the treatment with 50 mg L−1 of ZnO-NPs caused a decrease in the levels of chlorophyll a and b. Moreover, ZnO-NPs leaves significantly enhanced antioxidant enzymes activities. [ABSTRACT FROM AUTHOR]

Summary: Fenugreek microgreen and mint leaf displayed antidiabetic potential during in vitro assays including cell line‐based analysis. Aqueous fenugreek microgreen extract (FME) (2 mg mL−1) inhibited α‐amylase by 70%. It also enhanced glucose uptake in L6 cells by 25% at 10 mg mL−1 which further improved to 44% in the presence of insulin. On the other hand, fresh mint leaf extract (MLE) inhibited α‐glucosidase up to 90% and increased glucose uptake by 15% in HepG2 cells. Besides, both these extracts also inhibited nonenzymatic glycation of protein. FME and MLE were also found to have high levels of total phenolics, flavonoids and antioxidants which could play a possible role in the observed antidiabetic activity. As blood glucose levels in diabetes can be regulated by inhibition of enzymes regulating carbohydrate metabolism and improving glucose uptake in cells, the findings indicate a complimentary therapeutic role of these two dietary herbs in diabetes. [ABSTRACT FROM AUTHOR]

This study was conducted to elucidate the regulating mechanism of sodium nitroprussiate on seed germination and seedling growth of cherry tomato. After the treatment with different concentrations of sodium nitroprusside, the effects on the metabolites and key enzyme activities in carbon-nitrogen metabolism of cherry tomato cultivar Zhuyun as an experimental material were investigated. The results showed that from seed germination to seedling period, the contents of starch and total nitrogen decreased, but the contents of soluble sugar, reducing sugar, sucrose and soluble protein increased firstly and then decreased; and free amino acids content increased gradually. Sodium nitroprusside made the contents of starch, sucrose and fiee amino acids higher than CK. From seed germination to seedling period in cherry tomato, the activities of amylase, glutamine synthetase (GS) and sucrose phosphate synthase (SPS) decreased; the activities of nitrate reductase (NR) and glutamate synthase (GOGAT) increased at first and decreased then; and the CK and the 0.25 mmol/L sodium nitroprusside treatments exhibited decreased sucrose synthase (SS) activity, and the trend was increasing at first and decreasing then after the treatment with 0.50 and 1.00 mmol/L sodium nitroprusside. Sodium nitroprusside treatment improved amylase activity; and the carbon-nitrogen ratio of the CK increased at first and decreased then, while the values of other treatments tended to decrease. In addition, sodium nitroprusside did not affect seed germination potential and germination rate, but significantly improved biomass accumulation, root length and height of seedlings. These data suggest that sodium nitroprusside could affect the conversion of starch and sugar accumulation, delay the decomposition of total nitrogen and soluble protein, and achieve the effects of accelerating the accumulation of free amino acids, and promoting seed germination and seedling growth, and 0.50 mmol/L sodium nitroprusside has the best effect. [ABSTRACT FROM AUTHOR]

All living organisms communicate with their environment, and part of this dialogue is mediated by secondary messengers such as cyclic guanosine mono phosphate (cGMP). In plants, most of the specific components that allow production and breakdown of cGMP have now been identified apart from cGMP dependent phosphodiesterases, enzymes responsible for cGMP catabolism. Irrespectively, the role of cGMP in plant signal transductions is now firmly established with involvement of this nucleotide in development, stress response, ion homeostasis and hormone function. Within these areas, several consistent themes where cGMP may be particularly relevant are slowly emerging: these include regulation of cation fluxes, for example via cyclic nucleotide gated channels and in stomatal functioning. Many details of signalling pathways that incorporate cGMP remain to be unveiled. These include downstream targets other than a small number of ion channels, in particular cGMP dependent kinases. Improved genomics tools may help in this respect, especially since many proteins involved in cGMP signalling appear to have multiple and often overlapping functional domains which hampers identification on the basis of simple homology searches. Another open question regards the topographical distribution of cGMP signals are they cell limited? Does long distance cGMP signalling occur and if so, by what mechanisms? The advent of non-disruptive fluorescent reporters with high spatial and temporal resolution will provide a tool to accelerate progress in all these areas. Automation can facilitate large scale screens of mutants or the action of effectors that impact on cGMP signalling. [ABSTRACT FROM AUTHOR]

Terpenes are a multifarious group of secondary compounds present throughout the living world that function primarily in defence, or otherwise in regulating interactions between an organism and its environment. Terpene synthases (TPS) are a mid-sized gene family whose diversity and make-up reflects a plant's ecological requirements and unique adaptive history. Here we catalogue TPS in Melaleuca alternifolia and examine lineage-specific expansion in TPS relative to other sequenced Myrtaceae. Overall, far fewer (37) putative TPS genes were identified in M. alternifolia compared with Eucalyptus grandis (113) and E. globulus (106). The number of genes in clade TPS-b1 (12), which encode enzymes that produce cyclic monoterpenes, was proportionally larger in M. alternifolia than in any other well-characterised plant. Relative to E. grandis, the isoprene-/ocimene-producing TPS-b2 clade in M. alternifolia tended to be proportionally smaller. This suggested there may be lineage-specific subfamily change in Melaleuca relative to other sequenced Myrtaceae, perhaps as a consequence of its semi-aquatic evolutionary history. [ABSTRACT FROM AUTHOR]

Key message: Rice and chickpea GDPD s are transcriptionally influenced by mineral deficiencies; especially, by phosphate starvation and CaGDP1 encodes an active glycerophosphodiester phosphodiesterase enzyme. Abstract: Glycerophosphodiester phosphodiesterases (GDPDs) are enzymes involved in the degradation of glycerophosphodiesters into sn-glycerol-3-phosphate and corresponding alcohols. These phospholipid remodeling genes have been suggested to play important roles in phosphate homeostasis. However, comprehensive information about the role of GDPDs under low phosphate (P) and other nutrient deficiencies (N, K, Fe, Zn) in rice and chickpea is missing. Here, we identified 13 OsGDPDs and 6 CaGDPDs in rice and chickpea, respectively, and partly characterized their roles in multiple nutrient stresses. Expression profiling after 7 and 15 days of deficiency treatments revealed unique and overlapping differential expression patterns of OsGDPDs and CaGDPDs under different nutrient stresses. Principal component analysis on the expression patterns of OsGDPDs and CaGDPDs revealed their preferential role in P starvation. Some of the GDPDs were also induced by N, K, Fe and Zn deficiency in temporal manner in both crops suggesting their roles in multiple nutrient stresses. Biochemical characterization of highly responsive chickpea GDPD, CaGDPD1, confirmed its in vitro GDPD activity and revealed its optimal temperature, pH and cofactor requirements. Further, CaGDPD1 showed its accumulation in ER and endomembranes. We hereby propose CaGDPD1 and various OsGDPDs as low P responsive marker genes in chickpea and rice, respectively. Our data uphold role of GDPDs in multinutrient responses and suggest them as candidates for rice and chickpea improvement for tolerance to various nutrient deficiencies. [ABSTRACT FROM AUTHOR]

Rubisco activase (RCA) is essential for the activation of Rubisco, the carboxylating enzyme of photosynthesis. In Arabidopsis, RCA is composed of a large RCAα and small RCAβ isoform that are formed by alternative splicing of a single gene (At2g39730). The activity of Rubisco is controlled in response to changes in irradiance by regulation of RCA activity, which is known to involve a redox-sensitive disulfide bond located in the carboxy-terminal extension of the RCAα subunit. Additionally, phosphorylation of RCA threonine-78 (Thr-78) has been reported to occur in the dark suggesting that phosphorylation may also be associated with dark-inactivation of RCA and deactivation of Rubisco. In the present study, we developed site-specific antibodies to monitor phosphorylation of RCA at the Thr-78 site and used non-reducing SDS-PAGE to monitor the redox status of the RCAα subunit. By immunoblotting, phosphorylation of both RCA isoforms occurred at low light and in the dark and feeding peroxide or DTT to leaf segments indicated that redox status of the chloroplast stroma was a critical factor controlling RCA phosphorylation. Use of a knockout mutant identified the plastid-targeted casein kinase 2 (cpCK2α) as the major protein kinase involved in RCA phosphorylation. Studies with recombinant cpCK2α and synthetic peptide substrates identified acidic residues at the -1, +2, and +3 positions surrounding Thr-78 as strong positive recognition elements. The cpck2 knockout mutant had strongly reduced phosphorylation at the Thr-78 site but was similar to wild type plants in terms of induction kinetics of photosynthesis following transfer from darkness or low light to high light, suggesting that if phosphorylation of RCA Thr-78 plays a direct role it would be redundant to redox regulation for control of Rubisco activation state under normal conditions. [ABSTRACT FROM AUTHOR]

The plant cell wall (PCW) represents the most abundant renewable biomass resource for lignocellulosic ethanol production. Economical and efficient degradation of PCW to fermentable sugars is an essential subprocess during lignocellulosic ethanol production. At present, the recalcitrance of PCW to various pretreatments and enzymatic hydrolysis makes the PCW degradation unacceptably expensive. Engineering cell wall-degrading enzymes into growing plants provides a promising solution to lower the PCW degradation cost and increase its degradation efficiency for lignocellulosic ethanol production. Avoiding damage by the expressed biomass-degrading enzymes to growing plants is the key to successful use of this method. Two modern biological technologies can be used to solve this problem. One is to engineer a thermoregulated intein-modified cell wall-degrading enzyme into growing plants. The other is to use the genetimed expression technique. This editorial will give a brief discussion of opportunities and challenges of engineering cell wall-degrading enzymes into growing plants for improvement of lignocellulosic ethanol production. [ABSTRACT FROM AUTHOR]

NADPH is a key reductant carrier that maintains internal redox and antioxidant status, and that links biosynthetic, catabolic and signalling pathways. Plants have a mitochondrial external NADPH oxidation pathway, which depends on Ca2+ and pH in vitro, but concentrations of Ca2+ needed are not known. We have determined the K0.5(Ca2+) of the external NADPH dehydrogenase from Solanum tuberosum mitochondria and membranes of E. coli expressing Arabidopsis thaliana NDB1 over the physiological pH range using O2 and decylubiquinone as electron acceptors. The K0.5(Ca2+) of NADPH oxidation was generally higher than for NADH oxidation, and unlike the latter, it depended on pH. At pH 7.5, K0.5(Ca2+) for NADPH oxidation was high (≈100 μM), yet 20-fold lower K0.5(Ca2+) values were determined at pH 6.8. Lower K0.5(Ca2+) values were observed with decylubiquinone than with O2 as terminal electron acceptor. NADPH oxidation responded to changes in Ca2+ concentrations more rapidly than NADH oxidation did. Thus, cytosolic acidification is an important activator of external NADPH oxidation, by decreasing the Ca2+-requirements for NDB1. The results are discussed in relation to the present knowledge on how whole cell NADPH redox homeostasis is affected in plants modified for the NDB1 gene. [ABSTRACT FROM AUTHOR]

Small molecules (xenobiotics) that inhibit cell-wall-localised enzymes are valuable for elucidating the enzymes’ biological roles. We applied a high-throughput fluorescent dot-blot screen to search for inhibitors of Petroselinum xyloglucan endotransglucosylase (XET) activity in vitro . Of 4216 xenobiotics tested, with cellulose-bound xyloglucan as donor-substrate, 18 inhibited XET activity and 18 promoted it (especially anthraquinones and flavonoids). No compounds promoted XET in quantitative assays with (cellulose-free) soluble xyloglucan as substrate, suggesting that promotion was dependent on enzyme–cellulose interactions. With cellulose-free xyloglucan as substrate, we found 22 XET-inhibitors – especially compounds that generate singlet oxygen ( 1 O 2 ) e.g., riboflavin (IC 50 29 μM), retinoic acid, eosin (IC 50 27 μM) and erythrosin (IC 50 36 μM). The riboflavin effect was light-dependent, supporting 1 O 2 involvement. Other inhibitors included tannins, sulphydryl reagents and triphenylmethanes. Some inhibitors (vulpinic acid and brilliant blue G) were relatively specific to XET, affecting only two or three, respectively, of nine other wall-enzyme activities tested; others [e.g. (−)-epigallocatechin gallate and riboflavin] were non-specific. In vivo , out of eight XET-inhibitors bioassayed, erythrosin (1 μM) inhibited cell expansion in Rosa and Zea cell-suspension cultures, and 40 μM mycophenolic acid and (−)-epigallocatechin gallate inhibited Zea culture growth. Our work showcases a general high-throughput strategy for discovering wall-enzyme inhibitors, some being plant growth inhibitors potentially valuable as physiological tools or herbicide leads. [ABSTRACT FROM AUTHOR]

Twenty-four compounds, including the previously unknown artoxanthocarpuone A, artoxanthocarpuone B, hydroxylakoochin A, methoxylakoochin A, epoxylakoochin A, and artoxanthol, were isolated and characterized spectroscopically. Among them, artoxanthol is stilbene oligomer presumably constructed in a 5,11,12-triphenyl hexahydrochrysene scaffold by a Diels–Alder type of reaction, for which a biosynthetic pathway is proposed. Artoxanthol, alboctalol, steppogenin, norartocarpetin, resveratrol, oxyresveratrol, and chlorophorin potently inhibited mushroom tyrosinase activity with IC 50 values from 0.9 to 5.7 μM that were all far stronger than the positive controls. Artoxanthocarpuone A, artoxanthocarpuone B, methoxylakoochin A, lakoochin A, cudraflavone C, artonin A, resveratrol, and chlorophorin reduced tyrosinase activity and inhibited α-melanocyte-stimulating hormone-induced melanin production in B16F10 melanoma cells without affecting cell proliferation. Collectively, the results suggest that the constituents of Artocarpus xanthocarpus have potential to be used as depigmentation agents. [ABSTRACT FROM AUTHOR]

Aims: Heavy metals pollution is one of the most challenging problems to the environment and agricultural soils in recent decades. The purpose of the present work was to elucidate the effects of vanadium (V) on growth, V uptake, protein content and enzymes activity to sort out the V-tolerant and the sensitive genotypes of chickpea under hydroponic conditions. Methods: The activities of antioxidant enzymes (SOD, CAT, POD, and GSH, MDA) and protein contents were determined by using UV-1600 Spectrophotometer, and V concentration was determined by using GFAAS (GTA 120). Results: The findings show that V significantly increased the enzymes activities in all chickpea genotypes however, V significantly reduced the protein contents, and more accumulation of V was observed in roots than shoots in all genotypes. The plant biomass and lengths of roots and shoots were also significantly reduced by V. Moreover, NHVO caused more toxicity than NaVO. Conclusions: The previous studies report that higher activities of enzymes increase the tolerance of plants against stress. The obtained data of present study indicated that Noor-2009 and C-44 are tolerant and G-1 and Balkasar are sensitive genotypes of chickpea against V stress. [ABSTRACT FROM AUTHOR]

Main conclusion: Abscisic acid mediates the effect of post-anthesis soil drying on grain filling through regulating the activities of key enzymes and expressions of genes involved in sucrose-to-starch conversion in rice spikelets. This study investigated if abscisic acid (ABA) would mediate the effect of post-anthesis soil drying on grain filling through regulating the key enzymes in sucrose-to-starch conversion in rice ( Oryza sativa L.) spikelets. Two rice cultivars were field-grown. Three treatments, well-watered (WW), moderate soil drying (MD), and severe soil drying (SD), were imposed from 6 days after full heading until maturity. When compared with those under the WW, grain filling rate, grain weight, and sink activity, in terms of the activities and gene expression levels of sucrose synthase, ADP glucose pyrophosphorylase, starch synthase, and starch branching enzyme, in inferior spikelets were substantially increased under the MD, whereas they were markedly decreased in both superior and inferior spikelets under the SD. The two cultivars showed the same tendencies. Both MD and SD increased ABA content and expression levels of its biosynthesis genes in spikelets, with more increase under the SD than the MD. ABA content was significantly correlated with grain filling rate and sink activities under both WW and MD, while the correlations were not significant under the SD. Application of a low concentration ABA to WW plants imitated the results under the MD, and applying with a high concentration ABA showed the effect of the SD. The results suggest that ABA plays a vital role in grain filling through regulating sink activity and functions in a dose-dependent manner. An elevated ABA level under the MD enhances, whereas a too high level of ABA under the SD decreases, sink activity. [ABSTRACT FROM AUTHOR]

Suberin is a lipid-phenolic biopolyester deposited in the cell walls of certain boundary tissue layers of plants, such as root endodermis, root and tuber peridermis, and seed coats. Suberin serves as a protective barrier in these tissue layers, controlling, for example, water and ion transport. It is also a stress-induced anti-microbial barrier. The suberin polymer contains a variety of C16-C24 chain-length aliphatics, such as ω-hydroxy fatty acids, α,ω-dicarboxylic fatty acids, and primary fatty alcohols. Suberin also contains high amounts of glycerol and phenolics, especially ferulic acid. In addition, non-covalently linked waxes are likely associated with the suberin polymer. This review focusses on the suberin biosynthetic enzymes identified to date, which include β-ketoacyl-CoA synthases, fatty acyl reductases, long-chain acyl-CoA synthetases, cytochrome P450 monooxygenases, glycerol 3-phosphate acyltransferases, and phenolic acyltransferases. We also discuss recent advances in our understanding of the transport of suberin components intracellularly and to the cell wall, polymer assembly, and the regulation of suberin deposition. [ABSTRACT FROM AUTHOR]

Sawdust hemicellulosic hydrolysate can be used as a promising xylose source for enzymatic conversion to xylitol, a specialty product. The aim of this study was to design various factors by observing their effects on xylitol production from hemicellulosic hydrolysate by xylose reductase (XR) enzyme. The one-factor-at-a-time (OFAT) strategy was adopted to determine the effective levels of process factors influencing xylitol yield. Enzymatic xylitol production was conducted in batch mode using different levels of reaction time (2-18 h), temperature (20-70°C), pH (4.0-9.0), xylose concentration (9.4-37.6 g/L), NADPH concentration (1.17-5.32 g/L), enzyme concentration (2-6%), and agitation (50-150rpm). Among the factors examined, time, temperature, pH, NADPH, and enzyme concentration significantly influenced the biosynthesis of xylitol with the suitable level of 10 h, 30 °C, 7.0,3.66 g/L, and 3% (v/v), respectively. Xylitol yield obtained was 56% (w/w) under these observed optimum conditions. This is the first report on the bioproduction of xylitol from lignocellulosic substrate by XR. [ABSTRACT FROM AUTHOR]

Enzymatic hydrolysis is a widely used approach to improve the functional, nutritional and physiological properties of food proteins. In this study, cross-linked enzyme aggregates (CLEAs) have been prepared from cell-envelope proteinases (CEPs) of Lactobacillus delbruecfeii subsp. lactis 313 and their proteolytic properties have been evaluated using several food proteins. We have optimized cross-linking conditions including ammonium sulphate concentration, incubation temperatures, agitation speed, glutaraldehyde cross-linker concentration, reaction time and the addition of proteic feeders. Particularly, the presence of BSA improves retained activity of cross-linked CEP aggregates (CLCEPAs) from 21.5% to 40.9%. Blocking unreacted cross-linking groups on aggregates is important to enhance recyclability of CLCEPAs. CLCEPAs had attractive thermal stability at 50 °C and it showed enhanced catalytic activity over long-term storage after lyophilization. We have demonstrated that CLCEPAs has proteolytic properties on different food proteins including complex (chicken egg albumin, skimmed-milk protein), fractionated (bovine casein, whey protein isolate), and purified (bovine serum albumin) proteins. Being the first report of CLEAs from lactobacilli CEPs, this study demonstrates the feasibility of using LDL 313 CLCEPAs for degradation of various food proteins. [ABSTRACT FROM AUTHOR]

In plants sugar sensing and signal transduction involves pathways dependent or independent on HXK1 as a glucose sensor. Research was conducted to determine which pathway is responsible for regulation of the nitrate reduction. The effect of selected carbon and nitrogen metabolites on nitrate reductase (NR) activity in Arabidopsis thaliana wild type (WT) and hxk1 mutant roots was studied. Exogenously supplied sugar, sucrose (Suc) and organic acid, 2-oxoglutarate (2-OG) led to an increase in the total and actual activity of NR. It was due to both the increase in expression of NIA genes and NR activation state. The stimulatory effect of Suc and 2-OG on nitrate reduction was less pronounced in hxk1 mutant roots with T-DNA insertion in the AtHXK1 gene encoding hexokinase1 (HXK1) and characterized by reduced hexokinase activity and root level of G6P and F6P. On the other hand, it was shown that exogenous glucose did not mimic Suc-mediated NR activation in Arabidopsis roots. Taken together, this data suggest that the Suc signaling pathway might be independent from hexose's sensor dependent mechanism. [ABSTRACT FROM AUTHOR]

The RubisCO enzyme activity was studied in wheat cultivars exposed to salinity. Four Cuban varieties of wheat species T. aestivum and T. durum were selected and mounted two experimental variants in hydroponic conditions. He saline the first treatment with NaCl to a conductivity of 8 dS.m-1 in the nutrient solution, while in the control treatment (no applied NaCl for all cases) the pH of the solution was adjusted to 6.0. Treatments were applied from the time of planting to 35 days after seed germination when the determinations were made. As a result a significant decrease in RubisCO enzyme activity was obtained in all varieties in saline, where there were highly significant differences compared to the control treatment. Affectations than 10 % due to salinity were found. Wheat varieties of the species T. durum always occurred in the control treatment increased enzyme activity of RubisCO but the intensity of stress was higher in this species so it showed increased sensitivity to salinity compared to T. aestivum. [ABSTRACT FROM AUTHOR]

The article focuses on a study regarding the need of metabolic requirements for photo respiratory enzyme activities in heterotrophic tissues. Topics discussed are the role of photorespiration in avoiding the accumulation of 2-phosphoglycolate (2PG), analysis of expression of genes encoding photo respiratory enzymes and the presence of high transcripts levels of glycolate oxidase, alanine:glyoxylate aminotransferase 2 and glyoxylate reductase 1 in tissues.

Abstract: Transgenic tomato lines (cv. Kashi Vishesh) over-expressing AtDREB1A/CBF3 driven by stress-inducible rd29A promoter showed significantly higher activities of key antioxidant enzymes when exposed to water-deficit for 7, 14, and 21 days. Transgenic tomato plants exposed to water-deficit recorded lower levels of hydrogen peroxide and superoxide anion formation compared to the non-transgenic plants, suggesting alleviation of reactive oxygen species (ROS). A significant increase in activities of enzymes superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), glutathione reductase (GR), dehydroascorbate reductase (DHAR), and monodehydroascorbate reductase (MDHAR) was observed in response to the different durations of water-deficit conditions. In contrast, enzyme guaiacol peroxidase (POD) activity was lower in the transgenic lines and showed a negative correlation with ROS, ascorbic acid (AsA), and glutathione levels. The concentrations of AsA, glutathione and their reduced forms were higher in the transgenic plants and increased with ROS levels. These results indicate that AtDREB1A transgenic tomato lines are better adapted to water-deficit as they showed lower drought-induced oxidative stress due to activation of the antioxidant response. [Copyright &y& Elsevier]

Background: The mountain pine beetle (MPB, Dendroctonus ponderosae) epidemic has affected lodgepole pine (Pinus contorta) across an area of more than 18 million hectares of pine forests in western Canada, and is a threat to the boreal jack pine (Pinus banksiana) forest. Defence of pines against MPB and associated fungal pathogens, as well as other pests, involves oleoresin monoterpenes, which are biosynthesized by families of terpene synthases (TPSs). Volatile monoterpenes also serve as host recognition cues for MPB and as precursors for MPB pheromones. The genes responsible for terpene biosynthesis in jack pine and lodgepole pine were previously unknown. Results: We report the generation and quality assessment of assembled transcriptome resources for lodgepole pine and jack pine using Sanger, Roche 454, and Illumina sequencing technologies. Assemblies revealed transcripts for approximately 20,000 - 30,000 genes from each species and assembly analyses led to the identification of candidate full-length prenyl transferase, TPS, and P450 genes of oleoresin biosynthesis. We cloned and functionally characterized, via expression of recombinant proteins in E. coli, nine different jack pine and eight different lodgepole pine mono-TPSs. The newly identified lodgepole pine and jack pine mono-TPSs include (+)-α-pinene synthases, (-)-α-pinene synthases, (-)-β-pinene synthases, (+)-3-carene synthases, and (-)-β-phellandrene synthases from each of the two species. Conclusion: In the absence of genome sequences, transcriptome assemblies are important for defence gene discovery in lodgepole pine and jack pine, as demonstrated here for the terpenoid pathway genes. The product profiles of the functionally annotated mono-TPSs described here can account for the major monoterpene metabolites identified in lodgepole pine and jack pine. [ABSTRACT FROM AUTHOR]

Abstract: Vitamin B6 (pyridoxal 5′-phosphate and its vitamers) is an important cofactor in numerous enzymatic reactions. In spite of its importance, the consequences of altering vitamin B6 content on plant growth and development are not well understood. This study compares two mutants for vitamin B6-metabolizing enzymes in Arabidopsis thaliana: a pdx1.3 mutant in the de novo synthesis pathway and a salvage pathway sos4 mutant that accumulates more vitamin B6. We show that despite a difference in total B6 content in leaf tissue, both mutants share similar phenotypes, including chlorosis, decreased size, altered chloroplast ultrastructure, and root sensitivity to sucrose. Assay of B6 vitamer content from isolated chloroplasts showed that, despite differing B6 vitamer content in whole leaf tissue, both mutants share a common deficiency in total and phosphorylated vitamers in chloroplasts. One of the splice variants of the SOS4 proteins was shown to be located in the chloroplast. Our data indicate that some of the phenotypic consequences shared between the pdx1.3 and sos4 mutants are due to B6 deficiency in chloroplasts, and show that SOS4 is required for maintenance of phosphorylated B6 vitamer concentrations in chloroplasts. Further, our data are consistent with a diffusion model for transport of vitamin B6 into chloroplasts. [Copyright &y& Elsevier]

A new hypothesis is proposed to explain the metabolic regulation of intracellular pH (especially of the cytoplasm) in plants and replace the classic biochemical pH-stat [Davies (1973) Symp. Soc. Exp. Biol. 27: 513]. Alternative route glycolysis [Plaxton (1996) Annu. Rev. Plant Physiol. Plant Mol. Biol. 47: 185], alternative pathway respiration [Day et al. (1996) Plant Physiol. 110: 1], and malate-de-rived lactic and alcoholic fermentation (alternative pathway fermentation), all unique to plants, are organized into a novel mechanism that functions in toto as biochemical pH-stat. Its uniqueness to plants is examined from the evolutionary viewpoint that plants adopted the proton as the ion with which to create the electrochemical potential difference across the plasma membrane to energize uphill transports (“proton system”). The biochemical pH-stat is assumed to have evolved as a security mechanism for the “proton system” so that it could cope with the potential acidification of the cytoplasm under environmental stress. [ABSTRACT FROM AUTHOR]

In a recent paper (Ohana et al. 1998), we described the purification and structural characterization of a novel glycosidic triterpenoid saponin (GTS), a specific inhibitor of diguanylate cyclase (dgc), the key regulatory enzyme of the cellulose synthesizing apparatus of the bacterium Acetobacter xylinum. This compound and an identical or very similar one were isolated from pea (Pisum sativum), and A. xylinum respectively. We now present the effects of GTS on the kinetic properties of dgc. The observed inhibition is non-competitive with respect to the substrate GTP, is decreased by 50% in the presence of 20 μM c-di-GMP, and is not observed in the presence of various detergents. Photo-affinity labeling studies using [32P]c-di-GMP and purified enzyme showed that the inhibitor affects binding of c-di-GMP to dgc. It was ascertained that GTS, or at least a very similar compound, is present in other plant systems. The antibiotic Papulacandin B also inhibits dgc, although less efficiently than GTS (Ki = 70 μM vs. 5 μM). In in situ assays, highly purified GTS inhibits bacterial cellulose synthesis and dgc activity. Similary, digitonin permeabilized tobacco cell cultures display inhibition of glucan synthesis in the presence of GTS. [ABSTRACT FROM AUTHOR]