262,477 research outputs found
Myosin-cross-reactive antigen (MCRA) protein from Bifidobacterium breve is a FAD-dependent fatty acid hydratase which has a function in stress protection
Full text linkpeer-reviewedBackground The aim of this study was to determine the catalytic activity and physiological role of myosin-cross-reactive antigen (MCRA) from Bifidobacterium breve NCIMB 702258. MCRA from B. breve NCIMB 702258 was cloned, sequenced and expressed in heterologous hosts (Lactococcus and Corynebacterium) and the recombinant proteins assessed for enzymatic activity against fatty acid substrates. Results MCRA catalysed the conversion of palmitoleic, oleic and linoleic acids to the corresponding 10-hydroxy fatty acids, but shorter chain fatty acids were not used as substrates, while the presence of trans-double bonds and double bonds beyond the position C12 abolished hydratase activity. The hydroxy fatty acids produced were not metabolised further. We also found that heterologous Lactococcus and Corynebacterium expressing MCRA accumulated increasing amounts of 10-HOA and 10-HOE in the culture medium. Furthermore, the heterologous cultures exhibited less sensitivity to heat and solvent stresses compared to corresponding controls. Conclusions MCRA protein in B. breve can be classified as a FAD-containing double bond hydratase, within the carbon-oxygen lyase family, which may be catalysing the first step in conjugated linoleic acid (CLA) production, and this protein has an additional function in bacterial stress protection
Wound‐induced triacylglycerol biosynthesis is jasmonoy‐l‐isoleucin and abscisic acid independent
No full textTriacylglycerol (TAG) plays a significant role during plant stress – it maintains lipid homeostasis. Upon wounding plants accumulate TAG, likely as a storage form of fatty acids (FAs) that originate from damaged membranes. This study asked if this process depends on the two phytohormones jasmonoyl-isoleucine (JA-Ile) and abscisic acid (ABA), which are involved in wound signalling.
To analyse regulation of wound-induced TAG accumulation, we used mutants deficient in JA-Ile, with reduced ABA and the myb96 mutant, which is deficient in an ABA-dependent transcription factor. The expression of genes involved in TAG biosynthesis, and TAG content after wounding were analysed via LC–MS and GC-FID, plastidial lipid content in all mentioned mutant lines was also determined. The localization of newly synthesized TAG was investigated using lipid droplet staining.
TAG accumulation upon wounding was confirmed as well as the fact that the newly synthesized TAG are mostly composed of polyunsaturated fatty acids. Nevertheless, all tested mutant lines were able to accumulate TAG similar to the WT. We observed differences in reduction of plastidial lipids – in WT plants this was higher than in mutant lines. Newly synthesized TAGs were stored in lipid droplets at and around the wounded area.
Our results show that TAG accumulation upon wounding is not dependent on JA-Ile or ABA. The newly synthesized TAG species are composed of unsaturated fatty acids of membrane origin, and most likely serves as a transient energy store.Göttingen Graduate School of Neuroscience and Molecular Biology (GGNB)Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659Natural Sciences and Engineering Research Council of Canada http://dx.doi.org/10.13039/50110000003
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Full text linkThe biotrophic fungus Ustilago maydis causes smut disease in maize with characteristic tumor formation and anthocyanin induction. Here, we show that anthocyanin biosynthesis is induced by the virulence promoting secreted effector protein Tin2. Tin2 protein functions inside plant cells where it interacts with maize protein kinase ZmTTK1. Tin2 masks a ubiquitin-proteasome degradation motif in ZmTTK1, thus stabilizing the active kinase. Active ZmTTK1 controls activation of genes in the anthocyanin biosynthesis pathway. Without Tin2, enhanced lignin biosynthesis is observed in infected tissue and vascular bundles show strong lignification. This is presumably limiting access of fungal hyphae to nutrients needed for massive proliferation. Consistent with this assertion, we observe that maize brown midrib mutants affected in lignin biosynthesis are hypersensitive to U. maydis infection. We speculate that Tin2 rewires metabolites into the anthocyanin pathway to lower their availability for other defense responses
Phloem-Specific Expression of Yang Cycle Genes and Identification of Novel Yang Cycle Enzymes in<i>Plantago</i>and<i>Arabidopsis</i>
No full textAbstractThe 5-methylthioadenosine (MTA) or Yang cycle is a set of reactions that recycle MTA to Met. In plants, MTA is a byproduct of polyamine, ethylene, and nicotianamine biosynthesis. Vascular transcriptome analyses revealed phloem-specific expression of the Yang cycle gene 5-METHYLTHIORIBOSE KINASE1 (MTK1) in Plantago major and Arabidopsis thaliana. As Arabidopsis has only a single MTK gene, we hypothesized that the expression of other Yang cycle genes might also be vascular specific. Reporter gene studies and quantitative analyses of mRNA levels for all Yang cycle genes confirmed this hypothesis for Arabidopsis and Plantago. This includes the Yang cycle genes 5-METHYLTHIORIBOSE-1-PHOSPHATE ISOMERASE1 and DEHYDRATASE-ENOLASE-PHOSPHATASE-COMPLEX1. We show that these two enzymes are sufficient for the conversion of methylthioribose-1-phosphate to 1,2-dihydroxy-3-keto-5-methylthiopentene. In bacteria, fungi, and animals, the same conversion is catalyzed in three to four separate enzymatic steps. Furthermore, comparative analyses of vascular and nonvascular metabolites identified Met, S-adenosyl Met, and MTA preferentially or almost exclusively in the vascular tissue. Our data represent a comprehensive characterization of the Yang cycle in higher plants and demonstrate that the Yang cycle works primarily in the vasculature. Finally, expression analyses of polyamine biosynthetic genes suggest that the Yang cycle in leaves recycles MTA derived primarily from polyamine biosynthesis.</jats:p
Arabidopsis GH3 .10 conjugates jasmonates
No full textAbstract Jasmonates regulate plant development and defence. In angiosperms, the canonical bioactive jasmonate is jasmonoyl‐isoleucine (JA‐Ile), which is formed in Arabidopsis thaliana by JAR1 and GH3.10. In contrast to other jasmonate biosynthesis or perception mutants, however, gh3.10 jar1 knockout lines are still fertile. Therefore we investigated whether further jasmonates and GH3 enzymes contribute to regulation of fertility. Jasmonate levels were analysed by liquid chromatography–mass spectrometry. The substrate range of recombinant GH3.10 and related GH3 enzymes was studied using non‐targeted ex vivo metabolomics with flower and leaf extracts of A. thaliana and in vitro enzyme assays. Jasmonate application experiments were performed to study their potential bioactivity. In flowers and wounded leaves of gh3.10 jar1 knockout lines JA‐Ile was below the detection limit. While 12‐hydroxy‐JA was identified as the preferred substrate of GH3.10, no other recombinant GH3 enzymes tested were capable of JA‐Ile formation. Additional JA conjugates found in wounded leaves (JA‐Gln) or formed in flowers upon MeJA treatment in the absence of JA‐Ile (JA‐Gln, JA‐Asn, JA‐Glu) were identified. The aos gh3.10 jar1 was introduced as a novel tool to test for the bioactivity of JA‐Gln to regulate fertility. This study found JAR1 and GH3.10 are the only contributors to JA‐Ile biosynthesis in Arabidopsis and identified a number of JA conjugates as potential bioactive jasmonates acting in the absence of JA‐Ile. However, their contribution in regulating fertility is yet to be conclusively determined.Deutsche Forschungsgemeinschaft https://doi.org/10.13039/50110000165
Green light for lipid fingerprinting
No full textThe use of targeted lipidomic approaches for the analysis of plant lipids has steadily increased during recent years. We review recent developments of these methods and suggest the introduction of discovery lipidomics as additional approach through a new workflow, lipid fingerprinting, that integrates the advantages of shotgun lipidomics (quantitative data) with LC-MS-based strategies (higher resolution and/or coverage). This article is part of a Special Issue entitled:BBALIP_Lipidomics Opinion Articles edited by Sepp Kohlwein
progenies
No full textConditions in the parental environment during reproduction can affect the performance of the progenies. The goals of this study were to investigate whether warm or cold temperatures in the parental environment during flowering and seed development affect Arabidopsis thaliana seed properties, growth performance, reproduction and stress tolerance of the progenies, and to find candidate genes for progeny‐related differences in stress responsiveness. Parental plants were raised at 20 °C and maintained from bolting to seed maturity at warm (25 °C) or cold (15 °C) temperatures. Analysis of seed properties revealed significant increases in nitrogen in seeds from warm temperature and significant increases in lipids and in the ratio of α‐linolenic to oleic acid in seeds from the cold parental environment. Progenies of the warm parental environment showed faster germination rates, faster root elongation growth, higher leaf biomass and increased seed production at various temperatures compared with those from the cold parental environment. This indicates that under stable environmental conditions, progenies from warm parental environments had a clear adaptive advantage over those from cold parental environments. This parental effect was presumably transmitted by the higher nitrogen content of the seeds developed in warm conditions. When offspring from parents grown at different temperatures were exposed to chilling or freezing stress, photosynthetic yield recovered faster in progenies originating from cold parental environments. Cold acclimation involved up‐regulation of transcripts of flavanone 3‐hydroxylase (F3H) and pseudo response regulator 9 (PRR9) and down‐regulation of growth‐associated transcription factors (TFs) NAP and AP2domain containing RAP2.3. NAP, a regulator of senescence, and PRR9, a temperature‐sensitive modulator of the circadian clock, were probably involved in mediating parent‐of‐origin effects, because they showed progeny‐related expression differences under chilling. Because low temperatures also delay senescence, cold responsiveness of NAP suggests that this factor is linked with the regulatory network that is important for environmental acclimation of plants
Production of wax esters in plant seed oils by oleosomal cotargeting of biosynthetic enzymes
No full textWax esters are neutral lipids exhibiting desirable properties for lubrication. Natural sources have traditionally been whales. Additionally some plants produce wax esters in their seed oil. Currently there is no biological source available for long chain length monounsaturated wax esters that are most suited for industrial applications. This study aimed to identify enzymatic requirements enabling their production in oilseed plants. Wax esters are generated by the action of fatty acyl-CoA reductase (FAR), generating fatty alcohols and wax synthases (WS) that esterify fatty alcohols and acyl-CoAs to wax esters. Based on their substrate preference, a FAR and a WS from Mus musculus were selected for this study (MmFAR1 and Mm WS). Mm WS resides in the endoplasmic reticulum (ER), whereas MmFAR1 associates with peroxisomes. The elimination of a targeting signal and the fusion to an oil body protein yielded variants of MmFAR1 and Mm WS that were cotargeted and enabled wax ester production when coexpressed in yeast or Arabidopsis. In the fae1 fad2 double mutant, rich in oleate, the cotargeted variants of MmFAR1 and Mm WS enabled formation of wax esters containing >65% oleyl-oleate. The data suggest that cotargeting of unusual biosynthetic enzymes can result in functional interplay of heterologous partners in transgenic plants.-Heilmann, M., T. Iven, K. Ahmann, E. Hornung, S. Stymne, and I. Feussner. Production of wax esters in plant seed oils by oleosomal cotargeting of biosynthetic enzymes. J. Lipid Res. 2012. 53: 2153-2161
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