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1.
Suberin is a cell wall lipid polyester found in the cork cells of the periderm offering protection against dehydration and pathogens. Its biosynthesis and assembly, as well as its contribution to the sealing properties of the periderm, are still poorly understood. Here, we report on the isolation of the coding sequence CYP86A33 and the molecular and physiological function of this gene in potato (Solanum tuberosum) tuber periderm. CYP86A33 was down-regulated in potato plants by RNA interference-mediated silencing. Periderm from CYP86A33-silenced plants revealed a 60% decrease in its aliphatic suberin load and greatly reduced levels of C18:1 ω-hydroxyacid (approximately 70%) and α,ω-diacid (approximately 90%) monomers in comparison with wild type. Moreover, the glycerol esterified to suberin was reduced by 60% in the silenced plants. The typical regular ultrastructure of suberin, consisting of dark and light lamellae, disappeared and the thickness of the suberin layer was clearly reduced. In addition, the water permeability of the periderm isolated from CYP86A33-silenced lines was 3.5 times higher than that of the wild type. Thus, our data provide convincing evidence for the involvement of ω-functional fatty acids in establishing suberin structure and function.Periderm, the boundary tissue that replaces the epidermis in the secondary organs of plants, provides efficient protection against dehydration, UV radiation, and pathogens (Esau, 1965). Periderm is regularly found in the bark of woody plants, but herbaceous plants may also form a well-developed periderm in roots, tubers, and the oldest portions of stem. The periderm has been widely studied in potato (Solanum tuberosum) tubers because of the latter''s great agronomic significance (Schmidt and Schönherr, 1982; Vogt et al., 1983; Lulai and Freeman, 2001; Sabba and Lulai, 2002). Shrinkage and flaccidity occur in tubers if the protection afforded by the periderm against water loss is compromised (Lulai et al., 2006). Suberin and waxes embedded into the suberin matrix are considered essential for periderm imperviousness (Franke and Schreiber, 2007). Chemically, suberin is a complex lipid polymer consisting of a fatty acid-derived domain (aliphatic suberin) cross-linked by ester bonds to a polyaromatic lignin-like domain (aromatic suberin; Kolattukudy, 2001; Bernards, 2002; Franke and Schreiber, 2007). Aliphatic suberin has been widely analyzed in potato periderm (Kolattukudy and Agrawal, 1974; Graça and Pereira, 2000; Schreiber et al., 2005). The main monomers released from potato aliphatic suberin are a mixture of ω-hydroxyacids and α,ω-diacids with chain lengths ranging from C16 to C28 (mainly C18), together with glycerol. Small amounts of monofunctional fatty acids, alcohols, and ferulic acid are also released. Waxes are complex mixtures of lipids extractable with chloroform that in potato periderm consist mostly of linear very-long-chain aliphatics up to C32 (Schreiber et al., 2005). Suberin is deposited in the cell wall as a continuous deposit or secondary cell wall that overlays the polysaccharide primary cell wall from the inside (Esau, 1965). These suberin deposits appear under the transmission electron microscope (TEM) as regularly alternating opaque and translucent lamellae (Schmidt and Schönherr, 1982). Although several molecular models for suberin have been proposed (Kolattukudy, 1980; Bernards, 2002; Graça and Santos, 2007), how the suberin and wax components are organized in the lamellated suberin secondary cell wall is a matter of debate (Graça and Santos, 2007). Moreover, to what extent suberin and wax deposition and composition determine sealing properties of periderm still remains unclear (Schreiber et al., 2005). Several studies confirm the importance of waxes for the diffusion barrier (Soliday et al., 1979; Vogt et al., 1983; Schreiber et al., 2005), but the significance of aliphatic suberin has hardly been investigated at all. Interestingly, an Arabidopsis (Arabidopsis thaliana) knockout mutant for the GLYCEROL-3-PHOSPHATE ACYLTRANSFERASE5 gene (GPAT5) with altered suberin showed higher tetrazolium salt permeability in the seed coat (Beisson et al., 2007).ω-Hydroxylation of fatty acids, a reaction carried out in plants by cytochrome P450 monooxygenases, is a crucial step in the biosynthesis of plant biopolymers (Kolattukudy, 1980; Nawrath, 2002). The Arabidopsis mutant lacerata, which shows phenotype defects compatible with a cutin deficiency, is defective in CYP86A8 encoding a fatty acid ω-hydroxylase (Wellesen et al., 2001). The aberrant induction of type three genes1 (att1) mutant, showing an altered cuticle ultrastructure and a higher transpiration rate than wild type, is defective in CYP86A2 and contains reduced amounts of ω-functionalized cutin monomers (Xiao et al., 2004). Moreover, a genome-wide study of cork oak (Quercus suber) bark highlighted a member of the cytochrome P450 of the CYP86A subfamily as a strong candidate gene for aliphatic suberin biosynthesis (Soler et al., 2007); and a role for CYP86A1 in the biosynthesis of suberin has recently been confirmed in the primary root of Arabidopsis knockout mutants (Li et al., 2007; Hofer et al., 2008). However, how the lack of fatty acid ω-hydroxylase activity may affect the structural features and sealing properties of suberin in periderm cell walls has not been documented.To provide experimental evidence of the role of CYP86A genes in periderm fine structure and water transpiration properties, especially quantitative permeability studies so far unexplored in Arabidopsis, we followed a strategy based on the potato (cv Desirée). The potato is a model of choice for such studies because transgenic plants can be produced in reasonable time and sufficient amounts of periderm can easily be obtained from tubers for chemical and physiological studies (Vogt et al., 1983; Schreiber et al., 2005). Based on the CYP86A gene that was highlighted in cork oak periderm as a strong suberin candidate for aliphatic suberin biosynthesis, we isolated the putative ortholog in potato and used a reverse genetic approach to analyze the effects of down-regulation on the chemical and ultrastructural features of suberin and on the physiological properties of the tuber periderm. Our findings indicate that down-regulation of CYP86A33, as this gene was designated, results in a strong decrease of the ω-functionalized monomers in aliphatic suberin, which are necessary for the suberin typical lamellar organization and for the periderm resistance to water loss.  相似文献   

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Recent investigations have shown macromolecules, such as cutins, and suberins as effective markers for above and belowground plant tissues. These biopolyesters contain structural units specific for different litter components and for root biomass. The aim of this work was to understand the fate of plant organic matter (OM) in Mediterranean forest soils by evaluating the incorporation of cutin and suberin by measuring specific biomarkers. Soil and plant tissue (leaves, woods and roots) samples were collected in two mixed Mediterranean forests of Quercus ilex (holm oak) in costal stands in Tuscany (central Italy), which have different ecological and edaphic features. Ester-bound lipids of mineral and organic horizons and the overlying vegetation were analysed using the saponification method in order to depolymerise cutins and suberins and release their specific structural units. Cutin and suberin specific aliphatic monomers were identified and quantified by gas chromatographic techniques. The distribution of cutin and suberin specific monomers in plant tissue suggested that mid-chain hydroxy acids can be used as leaf-specific markers and α,ω-alkanedioic acids and ωC18:1 as root-specific markers. Differences in the distributions of biomarkers specific for above and belowground plant-derived OM was observed in the two types of soils, suggesting contrasted degradation, stabilisation and transport mechanisms that may be related to soil physico-chemical properties. The acidic and dry soil appeared to inhibit microbial activity, favouring stabilization of leaf-derived compounds, while, in the more fertile soil, protection within aggregates appeared to better preserve root-derived compounds.  相似文献   

4.
Wound‐induced suberin deposition involves the temporal and spatial coordination of phenolic and fatty acid metabolism. Phenolic metabolism leads to both soluble metabolites that accumulate as defense compounds as well as hydroxycinnamoyl derivatives that form the basis of the poly(phenolic) domain found in suberized tissue. Fatty acid metabolism involves the biosynthesis of very‐long‐chain fatty acids, 1‐alkanols, ω‐hydroxy fatty acids and α,ω‐dioic acids that form a poly(aliphatic) domain, commonly referred to as suberin. Using the abscisic acid (ABA) biosynthesis inhibitor fluridone (FD), we reduced wound‐induced de novo biosynthesis of ABA in potato tubers, and measured the impact on the expression of genes involved in phenolic metabolism (StPAL1, StC4H, StCCR, StTHT), aliphatic metabolism (StCYP86A33, StCYP86B12, StFAR3, StKCS6), metabolism linking phenolics and aliphatics (StFHT) or acyl chains and glycerol (StGPAT5, StGPAT6), and in the delivery of aliphatic monomers to the site of suberization (StABCG1). In FD‐treated tissue, both aliphatic gene expression and accumulation of aliphatic suberin monomers were delayed. Exogenous ABA restored normal aliphatic suberin deposition in FD‐treated tissue, and enhanced aliphatic gene expression and poly(aliphatic) domain deposition when applied alone. By contrast, phenolic metabolism genes were not affected by FD treatment, while FD + ABA and ABA treatments slightly enhanced the accumulation of polar metabolites. These data support a role for ABA in the differential induction of phenolic and aliphatic metabolism during wound‐induced suberization in potato.  相似文献   

5.
Insect double‐stranded (ds)RNA expression in transgenic crops can increase plant resistance to biotic stress; however, creating transgenic crops to defend against every insect pest is impractical. Arabidopsis Mob1A is required for organ growth and reproduction. When Arabidopsis roots were soaked in dsMob1A, the root lengths and numbers were significantly suppressed and plants could not bolt or flower. Twenty‐four hours after rice roots were immersed in fluorescent‐labelled dsEYFP (enhanced yellow fluorescent protein), fluorescence was observed in the rice sheath and stem and in planthoppers feeding on the rice. The expression levels of Ago and Dicer in rice and planthoppers were induced by dsEYFP. When rice roots were soaked in dsActin, their growth was also significantly suppressed. When planthoppers or Asian corn borers fed on rice or maize that had been irrigated with a solution containing the dsRNA of an insect target gene, the insect's mortality rate increased significantly. Our results demonstrate that dsRNAs can be absorbed by crop roots, trigger plant and insect RNAi and enhance piercing‐sucking and stem‐borer insect mortality rates. We also confirmed that dsRNA was stable under outdoor conditions. These results indicate that the root dsRNA soaking can be used as a bioinsecticide strategy during crop irrigation.  相似文献   

6.
Suberin composition of various plants including Arabidopsis (Arabidopsis thaliana) has shown the presence of very long chain fatty acid derivatives C20 in addition to the C16 and C18 series. Phylogenetic studies and plant genome mining have led to the identification of putative aliphatic hydroxylases belonging to the CYP86B subfamily of cytochrome P450 monooxygenases. In Arabidopsis, this subfamily is represented by CYP86B1 and CYP86B2, which share about 45% identity with CYP86A1, a fatty acid ω-hydroxylase implicated in root suberin monomer synthesis. Here, we show that CYP86B1 is located to the endoplasmic reticulum and is highly expressed in roots. Indeed, CYP86B1 promoter-driven β-glucuronidase expression indicated strong reporter activities at known sites of suberin production such as the endodermis. These observations, together with the fact that proteins of the CYP86B type are widespread among plant species, suggested a role of CYP86B1 in suberin biogenesis. To investigate the involvement of CYP86B1 in suberin biogenesis, we characterized an allelic series of cyp86B1 mutants of which two strong alleles were knockouts and two weak ones were RNA interference-silenced lines. These root aliphatic plant hydroxylase lines had a root and a seed coat aliphatic polyester composition in which C22- and C24-hydroxyacids and α,ω-dicarboxylic acids were strongly reduced. However, these changes did not affect seed coat permeability and ion content in leaves. The presumed precursors, C22 and C24 fatty acids, accumulated in the suberin polyester. These results demonstrate that CYP86B1 is a very long chain fatty acid hydroxylase specifically involved in polyester monomer biosynthesis during the course of plant development.  相似文献   

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Three C18 epoxy acids occur in plant cutins and suberins. 9,10-Epoxy-18-hydroxyoctadecanoic acid is a common constituent of both cutins and suberins whilst 9,10-epoxy-18-hydroxyoctadec-12-enoic acid is also present in some cutins. 9,10-Epoxyoctadecane-1,18-dioic acid occurs more commonly in suberins. Epoxy acids may comprise up to 60% of the total monomers obtained from some polymers. The epoxy compounds are readily converted into their corresponding alkoxyhydrin alkyl esters on depolymerization of cutin or suberin by alcoholysis. The chromatographic and MS properties of the alkoxyhydrin derivatives enable them to be readily distinguished from other cutin and suberin hydroxyfatty acids and to be used for the qualitative and quantitative determination of epoxy acids in the polymers.  相似文献   

12.
A gene coding for a class VII cytochrome P450 monooxygenase (CYP116B5) was identified from Acinetobacter radioresistens S13 growing on media with medium (C14, C16) and long (C24, C36) chain alkanes as the sole energy source. Phylogenetic analysis of its N‐ and C‐terminal domains suggests an evolutionary model involving a plasmid‐mediated horizontal gene transfer from the donor Rhodococcus jostii RHA1 to the receiving A. radioresistens S13. This event was followed by fusion and integration of the new gene in A. radioresistens chromosome. Heterologous expression of CYP116B5 in Escherichia coli BL21, together with the A. radioresistens Baeyer–Villiger monooxygenase, allowed the recombinant bacteria to grow on long‐ and medium‐chain alkanes, showing that CYP116B5 is involved in the first step of terminal oxidation of medium‐chain alkanes overlapping AlkB and in the first step of sub‐terminal oxidation of long‐chain alkanes. It was also demonstrated that CYP116B5 is a self‐sufficient cytochrome P450 consisting of a heme domain (aa 1–392) involved in the oxidation step of n‐alkanes degradation, and its reductase domain (aa 444–758) comprising the NADPH‐, FMN‐ and [2Fe2S]‐binding sites. To our knowledge, CYP116B5 is the first member of this class to have its natural substrate and function identified.  相似文献   

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Introduction – The plant cuticle is a thin, predominantly lipid layer that covers all primary aerial surfaces of vascular plants. The monomeric building blocks of the cutin biopolymer are mainly ω‐hydroxy fatty acids. Objective – Analysis of ω‐hydroxy fatty acids from cutin isolated from tomato fruits at different stages of decomposition in soil. Different derivatives and mass spectrometric techniques were used for peak identification and evaluation. Methodology – Preparation of purified cutin involving dewaxing and HCl treatment. Incubation of purified cutin for 20 months in soil. Pentafluorobenzoyl derivatives were used for GC/MS operated in the electron capture negative ion (ECNI) mode and trimethylsilyl ethers for GC/MS operated in the electron ionisation (EI) mode for analysis of ω‐hydroxy fatty acids. Results – Six ω‐hydroxy fatty acids were detected in the purified cutin, three of which were identified as degradation products of 9,16‐dihydroxyhexadecanoic acid as a consequence of the HCl treatment involved in the purification step. Incubation of the isolated cutin in soil was accompanied with decrease in concentration of all hydroxyl fatty acids. Conclusion – We produced evidence that the HCl treatment only affected free hydroxyl groups and thus could be used for proportioning free and bound OH‐groups on cutin fatty acids. The method enabled a direct quantification of the ω‐hydroxy fatty acids throughout the incubation phase. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

15.
The lipophilic biopolyester suberin forms important boundaries to protect the plant from its surrounding environment or to separate different tissues within the plant. In roots, suberin can be found in the cell walls of the endodermis and the hypodermis or periderm. Apoplastic barriers composed of suberin accomplish the challenge to restrict water and nutrient loss and prevent the invasion of pathogens. Despite the physiological importance of suberin and the knowledge of the suberin composition of many plants, very little is known about its biosynthesis and the genes involved. Here, a detailed analysis of the Arabidopsis aliphatic suberin in roots at different developmental stages is presented. This study demonstrates some variability in suberin amount and composition along the root axis and indicates the importance of omega-hydroxylation for suberin biosynthesis. Using reverse genetics, the cytochrome P450 fatty acid omega-hydroxylase CYP86A1 (At5g58860) has been identified as a key enzyme for aliphatic root suberin biosynthesis in Arabidopsis. The corresponding horst mutants show a substantial reduction in omega-hydroxyacids with a chain length 相似文献   

16.
Polymorphisms of CYP450 metabolizer enzymes and transport proteins play crucial roles in the inter‐individual variability of drug efficiency. The aim of our study was to predict the frequency of functional variants of CYP2D6, CYP2C19 and ABCB1 genes in the Hungarian population. One hundred twelve unrelated healthy subjects donated DNA sample in the study. ABCB1 C3435T and G2677T/A single‐nucleotide polymorphisms (SNPs) were determined by LightCycler polymerase chain reaction. Because only limited amount of data is available on the rare allelic variants of CYP2D6 in the European populations, our study applied an expanded set of CYP2D6 and CYP2C19 alleles by using AmpliChip test. Our results show that the CYP2D6 phenotypes were 1.9% ultra‐rapid metabolizer, 6.5% intermediate metabolizer (IM), 8.3% poor metabolizer (PM) and 83.3% extensive metabolizer (EM), and the CYP2C19 phenotypes were 1.8% PM, 31.2% IM and 67% EM. The prevalence of the commonly observed CYP2D6 and CYP2C19 alleles in our study corresponds with that of other European populations. Nevertheless, our study confirms that extending the CYP2D6 allele set with loss‐of‐function variants such as CYP2D6*7, *9, *41 is worth considering. Frequency of the wild type ABCB1 3435C was 42.8% whereas the prevelance of 2677 G was 50.4%. Although frequency data of G2677T/A SNP in the European area are limited, some discrepancies with other studies were found. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

17.
Salt exclusion at the roots and salt secretion in the leaves were examined in a mangrove, Avicennia officinalis. The non‐secretor mangrove Bruguiera cylindrica was used for comparative study of hydrophobic barrier formation in the roots. Bypass flow was reduced when seedlings were previously treated with high salt concentration. A biseriate exodermis was detected in the salt‐treated roots, along with an enhanced deposition of hydrophobic barriers in the endodermis. These barriers reduced Na+ loading into the xylem, accounting for a 90–95% salt exclusion in A. officinalis. Prominent barriers were found in the roots of B. cylindrica even in the absence of salt treatment. A cytochrome P450 gene that may regulate suberin biosynthesis was up‐regulated within hours of salt treatment in A. officinalis roots and leaves, corresponding with increased suberin deposition. X‐ray microanalysis showed preferential deposition of Na+ and Cl? in the root cortex compared with the stele, suggesting that the endodermis is the primary site of salt exclusion. Enhanced salt secretion and increased suberin deposition surrounding the salt glands were seen in the leaves with salt treatment. Overall, these data show that the deposition of apoplastic barriers increases resistance to bypass flow leading to efficient salt exclusion at the roots in mangroves.  相似文献   

18.

Key message

Potato StCYP86A33 complements the Arabidopsis AtCYP86A1 mutant, horst - 1.

Abstract

Suberin is a cell-wall polymer that comprises both phenolic and aliphatic components found in specialized plant cells. Aliphatic suberin is characterized by bi-functional fatty acids, typically ω-hydroxy fatty acids and α,ω-dioic acids, which are linked via glycerol to form a three-dimensional polymer network. In potato (Solanum tuberosum L.), over 65 % of aliphatics are either ω-hydroxy fatty acids or α,ω-dioic acids. Since the biosynthesis of α,ω-dioic acids proceeds sequentially through ω-hydroxy fatty acids, the formation of ω-hydroxy fatty acids represents a significant metabolic commitment during suberin deposition. Four different plant cytochrome P450 subfamilies catalyze ω-hydroxylation, namely, 86A, 86B, 94A, and 704B; though to date, only a few members have been functionally characterized. In potato, CYP86A33 has been identified and implicated in suberin biosynthesis through reverse genetics (RNAi); however, attempts to express the CYP86A33 protein and characterize its catalytic function have been unsuccessful. Herein, we describe eight fatty acid ω-hydroxylase genes (three CYP86As, one CYP86B, three CYP94As, and a CYP704B) from potato and demonstrate their tissue expression. We also complement the Arabidopsis cyp86A1 mutant horst-1 using StCYP86A33 under the control of the Arabidopsis AtCYP86A1 promoter. Furthermore, we provide preliminary analysis of the StCYP86A33 promoter using a hairy root transformation system to monitor pStCYP86A33::GUS expression constructs. These data confirm the functional role of StCYP86A33 as a fatty acid ω-hydroxylase, and demonstrate the utility of hairy roots in the study of root-specific genes.
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19.
p-Coumaric acid (4-hydroxycinnamic acid) and ferulic acid (4-hydroxy-3-methoxycinnamic acid) have been identified as constituents of cutin. Their reduction products were isolated from a phenolic fraction released from the cutin of the fruits of apple, peach, pear, and two varieties of tomato and apple leaf by treatment with LiAlH(4) or LiAlD(4). They were identified by combined gas chromatography and mass spectrometry. p-Coumaric acid was present in all samples of cutin (0.07-0.53% by weight), whereas only peach and pear cutin contained measurable amounts of ferulic acid (0.007% and 0.035%, respectively). Both p-coumaric acid and ferulic acid were identified to be constituents of the insoluble material recovered after partial hydrolysis (12-42% loss) of cutin in 1 m NaOH at 80 C. A significant part (48%) of the p-coumaric acid contained in tomato cutin was contained in the insoluble material recovered after partial degradation (7.4%) of this cutin with 0.01 m NaOH. These data indicate that these phenolic components are tightly (possibly covalently) bound to cutin. Similar analysis of the phenolic fractions from the suberins of potato, sweet potato, turnip, rutabaga, carrot, and red beet revealed that they contained only ferulic acid (0.05-0.22%). Ferulic acid was identified as a constituent of the insoluble material recovered after partial hydrolysis of potato and beet suberins (34% and 32% loss, respectively) in 1 m NaOH at 80 C. A major part (65%) of the ferulic acid contained in potato suberin was contained in the insoluble material recovered after partial (26.8% loss) degradation of this suberin with 0.01 m NaOH. Ferulic acid appears to be tightly (probably covalently) bound to suberin.  相似文献   

20.
This study investigates associations between gene expressions of aromatase (CYP19), 17α hydroxylase (CYP17), and estrogen receptors α and β and anthropometric measurements in offspring of the Michigan fish eater cohort. Leg and trunk length, height, weight, and BMI and gene expression in peripheral blood cells were measured in offspring of the Michigan fish eater cohort. The parental generation was followed between 1973 and 1991, and maternal age, height, and weight data were collected. Female offspring were contacted in 2001/2002 and followed up in 2006/2007; offspring information included age, education, reproductive history, smoking, and exercise. Gene expression was standardized against 18S ribosomal ribonucleic acid (18SrRNA) and RNA polymerase II (RNA PolII) expressions. Mixed models assessed the statistical effect of gene expression on anthropometric outcomes, accounting for multiple offspring from one mother. Anthropometric measurements and gene expression were measured in 139 female offspring. The two length and the height measurements were correlated, as were BMI and weight. CYP19 expression was correlated with the other gene expressions and both estrogen receptor expressions were associated. For every 1 unit of ΔCt (18SrRNACYP19) or ΔCt (RNA PolIICYP19), BMI was increased by 0.9 (P = 0.03) and 0.87 kg/m2 (P = 0.04), respectively, and weight by 2.35 kg (P = 0.03) and 2.1 kg (P = 0.03), respectively. For every 1 unit of ΔCt (18SrRNACYP17), leg length was increased by 0.84 cm (P = 0.04). The results suggest that CYP17 gene expression may influence growth during childhood and adolescence while CYP19 may be associated with the concurrent measures of weight and BMI.  相似文献   

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