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1.
J Plant Res ; 137(2): 255-264, 2024 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-38112982

RESUMO

The kinetic properties of Rubisco, a key enzyme for photosynthesis, have been examined in numerous plant species. However, this information on some plant groups, such as ferns, is scarce. This study examined Rubisco carboxylase activity and leaf Rubisco levels in seven ferns, including four Equisetum plants (E. arvense, E. hyemale, E. praealtum, and E. variegatum), considered living fossils. The turnover rates of Rubisco carboxylation (kcatc) in E. praealtum and E. hyemale were comparable to those in the C4 plants maize (Zea mays) and sorghum (Sorghum bicolor), whose kcatc values are high. Rubisco CO2 affinity, estimated from the percentage of Rubisco carboxylase activity under CO2 unsaturated conditions in kcatc in these Equisetum plants, was low and also comparable to that in maize and sorghum. In contrast, kcatc and CO2 affinities of Rubisco in other ferns, including E. arvense and E. variegatum were comparable with those in C3 plants. The N allocation to Rubisco in the ferns examined was comparable to that in the C3 plants. These results indicate that E. praealtum and E. hyemale have abundant Rubisco with high kcatc and low CO2 affinity, whereas the carboxylase activity and abundance of Rubisco in other ferns were similar to those in C3 plants. Herein, the Rubisco properties of E. praealtum and E. hyemale were discussed regarding their evolution and physiological implications.


Assuntos
Equisetum , Ribulose-Bifosfato Carboxilase , Dióxido de Carbono , Equisetum/metabolismo , Fotossíntese/fisiologia , Plantas/metabolismo , Zea mays/metabolismo
2.
Plant Mol Biol ; 113(6): 401-414, 2023 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-37129736

RESUMO

Plant cell walls are complex structures mainly made up of carbohydrate and phenolic polymers. In addition to their structural roles, cell walls function as external barriers against pathogens and are also reservoirs of glycan structures that can be perceived by plant receptors, activating Pattern-Triggered Immunity (PTI). Since these PTI-active glycans are usually released upon plant cell wall degradation, they are classified as Damage Associated Molecular Patterns (DAMPs). Identification of DAMPs imply their extraction from plant cell walls by using multistep methodologies and hazardous chemicals. Subcritical water extraction (SWE) has been shown to be an environmentally sustainable alternative and a simplified methodology for the generation of glycan-enriched fractions from different cell wall sources, since it only involves the use of water. Starting from Equisetum arvense cell walls, we have explored two different SWE sequential extractions (isothermal at 160 ºC and using a ramp of temperature from 100 to 160 ºC) to obtain glycans-enriched fractions, and we have compared them with those generated with a standard chemical-based wall extraction. We obtained SWE fractions enriched in pectins that triggered PTI hallmarks in Arabidopsis thaliana such as calcium influxes, reactive oxygen species production, phosphorylation of mitogen activated protein kinases and overexpression of immune-related genes. Notably, application of selected SWE fractions to pepper plants enhanced their disease resistance against the fungal pathogen Sclerotinia sclerotiorum. These data support the potential of SWE technology in extracting PTI-active fractions from plant cell wall biomass containing DAMPs and the use of SWE fractions in sustainable crop production.


Assuntos
Proteínas de Arabidopsis , Arabidopsis , Equisetum , Resistência à Doença , Proteínas de Arabidopsis/genética , Equisetum/metabolismo , Imunidade Vegetal , Biomassa , Arabidopsis/genética , Plantas/metabolismo , Parede Celular/metabolismo , Polissacarídeos/metabolismo , Doenças das Plantas/microbiologia
3.
Bioorg Chem ; 138: 106639, 2023 09.
Artigo em Inglês | MEDLINE | ID: mdl-37276680

RESUMO

Sixteen undescribed apocarotenoids (1-16), along with 22 known analogues, were isolated from the aerial parts of Equisetum debile. Their structures, including absolute configurations, were elucidated by NMR, HRESIMS, X-ray diffraction analysis, the modified Mosher's method and the quantum-chemical calculation of electronic circular dichroism (ECD) spectra. Compounds 1-9, 11-12 are the first example of C16-apocarotenoids appeared in nature. The plausible biosynthetic pathway of 1-16 was proposed. Moreover, the isolates were evaluated for their lipid-lowering activity, and the results showed that 13, 14, 15, 22, 31, 32 and 33 could remarkably decrease the levels of both TC and TG in FFA induced HepG2 cells at 20 µM. The oil red staining assay further demonstrated the lipid-lowering effects of 13, 14 and 15. The western blot results indicated that compounds 13, 14 and 15 could regulate the lipid metabolism via the activation of the AMPK/ACC/SREBP-1c signaling pathway. A preliminary structure-activity relationship (SAR) study of the isolates indicated that the apocarotenoids with 6/5 ring system displayed more potent lipid-lowering effects.


Assuntos
Equisetum , Metabolismo dos Lipídeos , Proteínas Quinases Ativadas por AMP/metabolismo , Proteína de Ligação a Elemento Regulador de Esterol 1/metabolismo , Proteína de Ligação a Elemento Regulador de Esterol 1/farmacologia , Equisetum/química , Equisetum/metabolismo , Transdução de Sinais , Lipídeos/farmacologia
4.
Plant J ; 105(6): 1549-1565, 2021 03.
Artigo em Inglês | MEDLINE | ID: mdl-33314395

RESUMO

Certain transglucanases can covalently graft cellulose and mixed-linkage ß-glucan (MLG) as donor substrates onto xyloglucan as acceptor substrate and thus exhibit cellulose:xyloglucan endotransglucosylase (CXE) and MLG:xyloglucan endotransglucosylase (MXE) activities in vivo and in vitro. However, missing information on factors that stimulate or inhibit these hetero-transglucosylation reactions limits our insight into their biological functions. To explore factors that influence hetero-transglucosylation, we studied Equisetum fluviatile hetero-trans-ß-glucanase (EfHTG), which exhibits both CXE and MXE activity, exceeding its xyloglucan:xyloglucan homo-transglucosylation (XET) activity. Enzyme assays employed radiolabelled and fluorescently labelled oligomeric acceptor substrates, and were conducted in vitro and in cell walls (in situ). With whole denatured Equisetum cell walls as donor substrate, exogenous EfHTG (extracted from Equisetum or produced in Pichia) exhibited all three activities (CXE, MXE, XET) in competition with each other. Acting on pure cellulose as donor substrate, the CXE action of Pichia-produced EfHTG was up to approximately 300% increased by addition of methanol-boiled Equisetum extracts; there was no similar effect when the same enzyme acted on soluble donors (MLG or xyloglucan). The methanol-stable factor is proposed to be expansin-like, a suggestion supported by observations of pH dependence. Screening numerous low-molecular-weight compounds for hetero-transglucanase inhibition showed that cellobiose was highly effective, inhibiting the abundant endogenous CXE and MXE (but not XET) action in Equisetum internodes. Furthermore, cellobiose retarded Equisetum stem elongation, potentially owing to its effect on hetero-transglucosylation reactions. This work provides insight and tools to further study the role of cellulose hetero-transglucosylation in planta by identifying factors that govern this reaction.


Assuntos
Celulose/metabolismo , Glucanos/metabolismo , Xilanos/metabolismo , Equisetum/enzimologia , Equisetum/metabolismo , Glicosídeo Hidrolases/metabolismo , Glicosiltransferases/metabolismo , Proteínas de Plantas/metabolismo , Brotos de Planta/metabolismo
5.
Plant Cell Physiol ; 62(12): 1839-1846, 2021 Dec 27.
Artigo em Inglês | MEDLINE | ID: mdl-34245308

RESUMO

Mixed ß(1,3;1,4)-linkage glucan (MLG) is commonly found in the monocot lineage, at particularly high levels in the Poaceae family, but also in the evolutionally distant genus, Equisetum. MLG has several properties that make it unique from other plant cell wall polysaccharides. It consists of ß1,4-linked polymers of glucose interspersed with ß1,3-linkages, but the presence of ß1,3-linkages provides quite different physical properties compared to its closest form of the cell wall component, cellulose. The mechanisms of MLG biosynthesis have been investigated to understand whether single or multiple enzymes are required to build mixed linkages in the glucan chain. Currently, MLG synthesis by a single enzyme is supported by mutagenesis analyses of cellulose synthase-like F6, the major MLG synthase, but further investigation is needed to gather mechanistic insights. Because of transient accumulation of MLG in elongating cells and vegetative tissues, several hypotheses have been proposed to explain the role of MLG in the plant cell wall. Studies have been carried out to identify gene expression regulators during development and light cycles as well as enzymes involved in MLG organization in the cell wall. A role of MLG as a storage molecule in grains is evident, but the role of MLG in vegetative tissues is still not well understood. Characterization of a cell wall component is difficult due to the complex heterogeneity of the plant cell wall. However, as detailed in this review, recent exciting research has made significant impacts in the understanding of MLG biology in plants.


Assuntos
Parede Celular/metabolismo , Equisetum/metabolismo , Glucanos/metabolismo , Poaceae/metabolismo
7.
Plant J ; 83(5): 753-69, 2015 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-26185964

RESUMO

Cell walls are metabolically active components of plant cells. They contain diverse enzymes, including transglycanases (endotransglycosylases), enzymes that 'cut and paste' certain structural polysaccharide molecules and thus potentially remodel the wall during growth and development. Known transglycanase activities modify several cell-wall polysaccharides (xyloglucan, mannans, mixed-linkage ß-glucan and xylans); however, no transglycanases were known to act on cellulose, the principal polysaccharide of biomass. We now report the discovery and characterization of hetero-trans-ß-glucanase (HTG), a transglycanase that targets cellulose, in horsetails (Equisetum spp., an early-diverging genus of monilophytes). HTG is also remarkable in predominantly catalysing hetero-transglycosylation: its preferred donor substrates (cellulose or mixed-linkage ß-glucan) differ qualitatively from its acceptor substrate (xyloglucan). HTG thus generates stable cellulose-xyloglucan and mixed-linkage ß-glucan-xyloglucan covalent bonds, and may therefore strengthen ageing Equisetum tissues by inter-linking different structural polysaccharides of the cell wall. 3D modelling suggests that only three key amino acid substitutions (Trp → Pro, Gly → Ser and Arg → Leu) are responsible for the evolution of HTG's unique specificity from the better-known xyloglucan-acting homo-transglycanases (xyloglucan endotransglucosylase/hydrolases; XTH). Among land plants, HTG appears to be confined to Equisetum, but its target polysaccharides are widespread, potentially offering opportunities for enhancing crop mechanical properties, such as wind resistance. In addition, by linking cellulose to xyloglucan fragments previously tagged with compounds such as dyes or indicators, HTG may be useful biotechnologically for manufacturing stably functionalized celluloses, thereby potentially offering a commercially valuable 'green' technology for industrially manipulating biomass.


Assuntos
Celulose/metabolismo , Equisetum/metabolismo , Glicosídeo Hidrolases/química , Glicosídeo Hidrolases/metabolismo , Proteínas Recombinantes/metabolismo , Substituição de Aminoácidos , Clonagem Molecular , Equisetum/genética , Evolução Molecular , Glicosídeo Hidrolases/genética , Glicosiltransferases/metabolismo , Pichia/genética , Proteínas de Plantas/química , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Conformação Proteica , Proteínas Recombinantes/genética , Homologia Estrutural de Proteína , Especificidade por Substrato
8.
J Proteome Res ; 14(4): 1779-91, 2015 Apr 03.
Artigo em Inglês | MEDLINE | ID: mdl-25716083

RESUMO

The rhizome is responsible for the invasiveness and competitiveness of many plants with great economic and agricultural impact worldwide. Besides its value as an invasive organ, the rhizome plays a role in the establishment and massive growth of forage, providing biomass for biofuel production. Despite these features, little is known about the molecular mechanisms that contribute to rhizome growth, development, and function in plants. In this work, we characterized the proteome of rhizome apical tips and elongation zones from different species using a GeLC-MS/MS (one-dimensional electrophoresis in combination with liquid chromatography coupled online with tandem mass spectrometry) spectral-counting proteomics strategy. Five rhizomatous grasses and an ancient species were compared to study the protein regulation in rhizomes. An average of 2200 rhizome proteins per species were confidently identified and quantified. Rhizome-characteristic proteins showed similar functional distributions across all species analyzed. The over-representation of proteins associated with central roles in cellular, metabolic, and developmental processes indicated accelerated metabolism in growing rhizomes. Moreover, 61 rhizome-characteristic proteins appeared to be regulated similarly among analyzed plants. In addition, 36 showed conserved regulation between rhizome apical tips and elongation zones across species. These proteins were preferentially expressed in rhizome tissues regardless of the species analyzed, making them interesting candidates for more detailed investigative studies about their roles in rhizome development.


Assuntos
Equisetum/genética , Proteínas de Plantas/análise , Poaceae/genética , Proteoma/genética , Proteoma/metabolismo , Proteômica/métodos , Rizoma/metabolismo , Cromatografia Líquida , Eletroforese em Gel de Poliacrilamida , Equisetum/metabolismo , Proteínas de Plantas/classificação , Proteínas de Plantas/metabolismo , Poaceae/metabolismo , Rizoma/genética , Especificidade da Espécie , Espectrometria de Massas em Tandem
9.
J Fluoresc ; 25(3): 595-601, 2015 May.
Artigo em Inglês | MEDLINE | ID: mdl-25779939

RESUMO

Unicellular model plant systems (vegetative microspores of horsetail Equisetum arvense and pollen of six plant species Corylus avellana, Dolichothele albescens Populus balsamifera, Salix caprea, Saintpaulia ionantha, Tulipa hybridum, on which autofluorescence and fluorescence after histochemical treatment studied, have been represented as bioindicators of ozone. It has found that low doses of ozone 0.005 or 0.008 µl/l did not affect or stimulate the autofluorescence of the samples with the ability to germinate in an artificial medium. In higher ozone concentrations (0.032 µl/l) either the decrease in the intensity of the emission or changing in the position of the maxima in the fluorescence spectrum (new 515-520 nm maximum characteristic for the green-and yellow area has appeared) were observed. In dose of 0.2 µl/l, higher than above the threshold of danger to human health, autofluorescence in all samples fell down to up to zero, and there was no the ability to germinate. In this case the formation of lipofuscin-like compounds fluoresced in blue with maxima from 440 to 485 nm was observed. Stress metabolites, known as neurotransmitters biogenic amines, were found in treated cells as determined on the characteristic fluorescence at 460-480 nm in the samples after a specific histochemical reactions for catecholamines (with glyoxylic acid) or for histamine (with o-phthalic aldehyde). Increased intensity of the emission under the treatment with ozone (total doses from 0.012 to 0.032 µl/l) was associated with an increase in the concentrations of catecholamines and histamine. The fluorescent analysis on undamaged cells-possible bioindicators of ozone can be useful in ecomonitoring for earlier warning about health hazardous concentrations of this compound in the air.


Assuntos
Equisetum/metabolismo , Modelos Teóricos , Neurotransmissores/análise , Ozônio/análise , Plantas/metabolismo , Esporos/metabolismo , Aminas/análise , Equisetum/crescimento & desenvolvimento , Fluorescência , Humanos , Plantas/química , Pólen/crescimento & desenvolvimento , Pólen/metabolismo , Espectrometria de Fluorescência , Esporos/crescimento & desenvolvimento
10.
Plant Physiol Biochem ; 210: 108606, 2024 May.
Artigo em Inglês | MEDLINE | ID: mdl-38615440

RESUMO

The aim was to use the agricultural weed and silica (Si) hyperaccumulator Equisetum arvense as Si fertilizer in plant cultivation. We investigated (1) the Si uptake in various Equisetum species, (2) where Si accumulates in the Equisetum plant, (3) processing methods to release as much Si as possible from dried, ground E. arvense plants and (4) which treatment yields gives the highest uptake of Si in young wheat plants cultivated in soil containing ground E. arvense. The results showed that E. arvense containes 22% Si and was among the best Si accumulators. Equisetum arvense accumulates Si as both soluble and firmly bound fractions. Amorphous silica (SiO2) accumulates in the outer cell walls of epidermis of the entire plant. Regarding the processing method, a longer treatment time, greater concentration of Equisetum, boiling, and the addition of sodium bicarbonate increased the Si availability in ground, dried E. arvense. The addition of untreated, ground, dried E. arvense to the soil, corresponding to 160 kg Si ha-1, increased the available Si in the soil and the Si uptake in wheat plants by five-fold, compared with the control. Boiling the ground E. arvense increased the Si uptake by 10 times, and the of sodium bicarbonate increased the availability and uptake by 40 times, compared with the control. In conclusion, dried, ground E. arvense can be used as a Si fertilizer as is, after boiling for a slightly better effect, or with sodium bicarbonate (up to a similar amount as the ground material) for best effect.


Assuntos
Equisetum , Fertilizantes , Dióxido de Silício , Equisetum/metabolismo , Dióxido de Silício/metabolismo , Triticum/metabolismo , Triticum/crescimento & desenvolvimento , Solo/química
11.
Plant J ; 72(2): 320-30, 2012 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-22712876

RESUMO

Plants benefit greatly from silicon (Si) absorption provided that they contain Si transporters. The latter have recently been identified in the roots of some higher plants known to accumulate high concentrations of Si, and all share a high level of sequence identity. In this study, we searched for transporters in the primitive vascular plant Equisetum arvense (horsetail), which is a valuable but neglected model plant for the study of Si absorption, as it has one of the highest Si concentrations in the plant kingdom. Our initial attempts to identify Si transporters based on sequence homology with transporters from higher plants proved unsuccessful, suggesting a divergent structure or property in horsetail transporters. Subsequently, through sequencing of the horsetail root transcriptome and a search using amino acid sequences conserved in plant aquaporins, we were able to identify a multigene family of aquaporin Si transporters. Comparison of known functional domains and phylogenetic analysis of sequences revealed that the horsetail proteins belong to a different group than higher-plant Si transporters. In particular, the newly identified proteins contain a STAR pore as opposed to the GSGR pore common to all previously identified Si transporters. In order to determine its functionality, the proteins were heterologously expressed in both Xenopus oocytes and Arabidopsis, and the results showed that the horsetail proteins are extremely efficient a transporting Si. These findings offer new insights into the elusive properties of Si and its absorption by plants.


Assuntos
Aquaporinas/genética , Equisetum/genética , Família Multigênica , Silício/metabolismo , Sequência de Aminoácidos , Animais , Aquaporinas/metabolismo , Arabidopsis/genética , Arabidopsis/metabolismo , Sequência de Bases , Transporte Biológico , Equisetum/metabolismo , Feminino , Expressão Gênica , Modelos Moleculares , Dados de Sequência Molecular , Oócitos , Especificidade de Órgãos , Filogenia , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Raízes de Plantas/genética , Raízes de Plantas/metabolismo , Brotos de Planta/genética , Brotos de Planta/metabolismo , Estrutura Terciária de Proteína , RNA de Plantas/genética , Alinhamento de Sequência , Análise de Sequência de DNA , Transcriptoma , Xenopus/genética , Xenopus/metabolismo
12.
Ann Bot ; 109(5): 873-86, 2012 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-22378839

RESUMO

BACKGROUND AND AIMS: Horsetails (Equisetopsida) diverged from other extant eusporangiate monilophytes in the Upper Palaeozoic. They are the only monilophytes known to contain the hemicellulose mixed-linkage (1 → 3, 1 → 4)-ß-d-glucan (MLG), whereas all land plants possess xyloglucan. It has been reported that changes in cell-wall chemistry often accompanied major evolutionary steps. We explored changes in hemicelluloses occurring during Equisetum evolution. METHODS: Hemicellulose from numerous monilophytes was treated with lichenase and xyloglucan endoglucanase. Lichenase digests MLG to di-, tri- and tetrasaccharide repeat-units, resolvable by thin-layer chromatography. KEY RESULTS: Among monilophytes, MLG was confined to horsetails. Our analyses support a basal trichotomy of extant horsetails: MLG was more abundant in subgenus Equisetum than in subgenus Hippochaete, and uniquely the sister group E. bogotense yielded almost solely the tetrasaccharide repeat-unit (G4G4G3G). Other species also gave the disaccharide, whereas the trisaccharide was consistently very scarce. Tetrasaccharide : disaccharide ratios varied interspecifically, but with no consistent difference between subgenera. Xyloglucan was scarce in Psilotum and subgenus Equisetum, but abundant in subgenus Hippochaete and in the eusporangiate ferns Marattia and Angiopteris; leptosporangiate ferns varied widely. All monilophytes shared a core pattern of xyloglucan repeat-units, major XEG products co-chromatographing on thin-layer chromatography with non-fucosylated hepta-, octa- and nonasaccharides and fucose-containing nona- and decasaccharides. CONCLUSIONS: G4G4G3G is the ancestral repeat-unit of horsetail MLG. Horsetail evolution was accompanied by quantitative and qualitative modification of MLG; variation within subgenus Hippochaete suggests that the structure and biosynthesis of MLG is evolutionarily plastic. Xyloglucan quantity correlates negatively with abundance of other hemicelluloses; but qualitatively, all monilophyte xyloglucans conform to a core pattern of repeat-unit sizes.


Assuntos
Parede Celular/química , Equisetum/química , Glucanos/química , Polissacarídeos/química , Xilanos/química , beta-Glucanas/química , Evolução Biológica , Parede Celular/metabolismo , Celulase/metabolismo , Cromatografia em Camada Fina , Equisetum/genética , Equisetum/metabolismo , Glucanos/metabolismo , Glicosídeo Hidrolases/metabolismo , Filogenia , Polissacarídeos/classificação , Polissacarídeos/metabolismo , Traqueófitas/química , Traqueófitas/genética , Traqueófitas/metabolismo , Xilanos/metabolismo , beta-Glucanas/classificação , beta-Glucanas/metabolismo
13.
BMC Plant Biol ; 11: 112, 2011 Jul 29.
Artigo em Inglês | MEDLINE | ID: mdl-21801378

RESUMO

BACKGROUND: The horsetails (Equisetum sp) are known biosilicifiers though the mechanism underlying silica deposition in these plants remains largely unknown. Tissue extracts from horsetails grown hydroponically and also collected from the wild were acid-digested in a microwave oven and their silica 'skeletons' visualised using the fluor, PDMPO, and fluorescence microscopy. RESULTS: Silica deposits were observed in all plant regions from the rhizome through to the stem, leaf and spores. Numerous structures were silicified including cell walls, cell plates, plasmodesmata, and guard cells and stomata at varying stages of differentiation. All of the major sites of silica deposition in horsetail mimicked sites and structures where the hemicellulose, callose is known to be found and these serendipitous observations of the coincidence of silica and callose raised the possibility that callose might be templating silica deposition in horsetail. Hydroponic culture of horsetail in the absence of silicic acid resulted in normal healthy plants which, following acid digestion, showed no deposition of silica anywhere in their tissues. To test the hypothesis that callose might be templating silica deposition in horsetail commercially available callose was mixed with undersaturated and saturated solutions of silicic acid and the formation of silica was demonstrated by fluorimetry and fluorescence microscopy. CONCLUSIONS: The initiation of silica formation by callose is the first example whereby any biomolecule has been shown to induce, as compared to catalyse, the formation of silica in an undersaturated solution of silicic acid. This novel discovery allowed us to speculate that callose and its associated biochemical machinery could be a missing link in our understanding of biosilicification.


Assuntos
Equisetum/metabolismo , Dióxido de Silício/metabolismo , Parede Celular/química , Parede Celular/metabolismo , Equisetum/química , Equisetum/citologia , Microscopia de Fluorescência/métodos , Folhas de Planta/química , Folhas de Planta/citologia , Folhas de Planta/metabolismo , Caules de Planta/química , Caules de Planta/citologia , Caules de Planta/metabolismo , Estômatos de Plantas/química , Estômatos de Plantas/citologia , Estômatos de Plantas/metabolismo , Rizoma/química , Rizoma/citologia , Rizoma/metabolismo , Dióxido de Silício/análise
14.
New Phytol ; 190(2): 387-97, 2011 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-21106036

RESUMO

• The very high rates of convective ventilation reported recently in Equisetum telmateia (up to 120 cm(3) min(-1); internal wind speed, 10 cm s(-1)) prompted this study of a further eight species for the presence or absence of convection and the possible reasons for this. • Convection rates were examined in relation to anatomical pathways, internal resistance to applied pressurized gas flow and stomata. • Only species with interconnecting cortical aerenchyma in branches (when present), shoots and rhizomes induced convection. Rapid humidity-induced convection (HIC) occurred in E. palustre (up to 13 cm(3) min(-1)), with slower rates in E. × schaffneri and E. ramosissimum (≤ 6 and 3 cm(3) min(-1), respectively). Excised shoots of E. hyemale and E. fluviatile showed the potential for HIC (≤ 0.5 and 0.15 cm(3) min(-1), respectively), but not into the rhizomes. High rates were linked to low internal gas flow resistance. No convection was detected in E. scirpoides, E. sylvaticum or E. arvense due to the extremely high resistance to pressure flow, for example, from intercalary meristems and, in the last two, to nonaerenchymatous branches. • Of the nine Equisetum species studied so far, four showed through-flow convection; the other species must rely solely on diffusion for underground aeration in wet soils.


Assuntos
Convecção , Equisetum/metabolismo , Pressão , Aerobiose , Equisetum/anatomia & histologia , Equisetum/ultraestrutura , Modelos Biológicos , Caules de Planta/anatomia & histologia , Estômatos de Plantas/metabolismo , Estômatos de Plantas/ultraestrutura , Reologia , Especificidade da Espécie
15.
Ann Bot ; 108(2): 307-19, 2011 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-21752793

RESUMO

BACKGROUND AND AIMS: The anatomy of Equisetum stems is characterized by the occurrence of vallecular and carinal canals. Previous studies on the carinal canals in several Equisetum species suggest that they convey water from one node to another. METHODS: Cell wall composition and ultrastructure have been studied using immunocytochemistry and electron microscopy, respectively. Serial sectioning and X-ray computed tomography were employed to examine the internode-node-internode transition of Equisetum ramosissimum. KEY RESULTS: The distribution of the LM1 and JIM20 extensin epitopes is restricted to the lining of carinal canals. The monoclonal antibodies JIM5 and LM19 directed against homogalacturonan with a low degree of methyl esterification and the CBM3a probe recognizing crystalline cellulose also bound to this lining. The xyloglucan epitopes recognized by LM15 and CCRC-M1 were only detected in this lining after pectate lyase treatment. The carinal canals, connecting consecutive rings of nodal xylem, are formed by the disruption and dissolution of protoxylem elements during elongation of the internodes. Their inner surface appears smooth compared with that of vallecular canals. CONCLUSIONS: The carinal canals in E. ramosissimum have a distinctive lining containing pectic homogalacturonan, cellulose, xyloglucan and extensin. These canals might function as water-conducting channels which would be especially important during the elongation of the internodes when protoxylem is disrupted and the metaxylem is not yet differentiated. How the molecularly distinct lining relates to the proposed water-conducting function of the carinal canals requires further study. Efforts to elucidate the spatial and temporal distribution of cell wall polymers in a taxonomically broad range of plants will probably provide more insight into the structural-functional relationships of individual cell wall components or of specific configurations of cell wall polymers.


Assuntos
Aquaporinas/metabolismo , Parede Celular/química , Parede Celular/ultraestrutura , Equisetum/metabolismo , Glicoproteínas/metabolismo , Proteínas de Plantas/metabolismo , Imunoquímica/métodos , Microscopia Eletrônica/métodos , Reguladores de Crescimento de Plantas/metabolismo , Fenômenos Fisiológicos Vegetais , Espanha , Tomografia Computadorizada por Raios X/métodos
16.
Mol Plant ; 13(7): 1047-1062, 2020 07 06.
Artigo em Inglês | MEDLINE | ID: mdl-32376294

RESUMO

Current cell-wall models assume no covalent bonding between cellulose and hemicelluloses such as xyloglucan or mixed-linkage ß-d-glucan (MLG). However, Equisetum hetero-trans-ß-glucanase (HTG) grafts cellulose onto xyloglucan oligosaccharides (XGOs) - and, we now show, xyloglucan polysaccharide - in vitro, thus exhibiting CXE (cellulose:xyloglucan endotransglucosylase) activity. In addition, HTG also catalyzes MLG-to-XGO bonding (MXE activity). In this study, we explored the CXE action of HTG in native plant cell walls and tested whether expansin exposes cellulose to HTG by disrupting hydrogen bonds. To quantify and visualize CXE and MXE action, we assayed the sequential release of HTG products from cell walls pre-labeled with substrate mimics. We demonstrated covalent cellulose-xyloglucan bonding in plant cell walls and showed that CXE and MXE action was up to 15% and 60% of total transglucanase action, respectively, and peaked in aging, strengthening tissues: CXE in xylem and cells bordering intercellular canals and MXE in sclerenchyma. Recombinant bacterial expansin (EXLX1) strongly augmented CXE activity in vitro. CXE and MXE action in living Equisetum structural tissues potentially strengthens stems, while expansin might augment the HTG-catalyzed CXE reaction, thereby allowing efficient CXE action in muro. Our methods will enable surveys for comparable reactions throughout the plant kingdom. Furthermore, engineering similar hetero-polymer formation into angiosperm crop plants may improve certain agronomic traits such as lodging tolerance.


Assuntos
Parede Celular/metabolismo , Celulose/metabolismo , Equisetum/metabolismo , Glucanos/metabolismo , Glicosídeo Hidrolases/metabolismo , Proteínas de Plantas/metabolismo , Xilanos/metabolismo , Equisetum/enzimologia , Glicosiltransferases/metabolismo , Ligação de Hidrogênio
17.
J Plant Physiol ; 251: 153210, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32544741

RESUMO

Transglycanases are enzymes that remodel the primary cell wall in plants, potentially loosening and/or strengthening it. Xyloglucan endotransglucosylase (XET; EC 2.4.1.207), ubiquitous in land plants, is a homo-transglucanase activity (donor, xyloglucan; acceptor, xyloglucan) exhibited by XTH (xyloglucan endotransglucosylase/hydrolase) proteins. By contrast, hetero-trans-ß-glucanase (HTG) is the only known enzyme that is preferentially a hetero-transglucanase. Its two main hetero-transglucanase activities are MLG : xyloglucan endotransglucosylase (MXE) and cellulose : xyloglucan endotransglucosylase (CXE). HTG is highly acidic and found only in the evolutionarily isolated genus of fern-allies, Equisetum. We now report genes for three new highly acidic HTG-related XTHs in E. fluviatile (EfXTH-A, EfXTH-H and EfXTH-I). We expressed them heterologously in Pichia and tested the encoded proteins' enzymic activities to determine whether their acidity and/or their Equisetum-specific sequences might confer high hetero-transglucanase activity. Untransformed Pichia was found to secrete MLG-degrading enzyme(s), which had to be removed for reliable MXE assays. All three acidic EfXTHs exhibited very predominantly XET activity, although low but measurable hetero-transglucanase activities (MXE and CXE) were also detected in EfXTH-H and EfXTH-I. We conclude that the extremely high hetero-transglucanase activities of Equisetum HTG are not emulated by similarly acidic Equisetum XTHs that share up to 55.5% sequence identity with HTG.


Assuntos
Equisetum/genética , Glicosiltransferases/genética , Proteínas de Plantas/genética , Sequência de Aminoácidos , Equisetum/metabolismo , Glicosiltransferases/química , Glicosiltransferases/metabolismo , Filogenia , Proteínas de Plantas/química , Proteínas de Plantas/metabolismo , Alinhamento de Sequência , Especificidade por Substrato
18.
Plant J ; 54(3): 510-21, 2008 May.
Artigo em Inglês | MEDLINE | ID: mdl-18284587

RESUMO

Mixed-linkage (1-->3),(1-->4)-beta-D-glucan (MLG) is widely considered to be a defining feature of the cell walls of plants in the Poales order. However, we conducted an extensive survey of cell-wall composition in diverse land plants and discovered that MLG is also abundant in the walls of the horsetail Equisetum arvense. MALDI-TOF MS and monosaccharide linkage analysis revealed that MLG in E. arvense is an unbranched homopolymer that consists of short blocks of contiguous 1,4-beta-linked glucose residues joined by 1,3-beta linkages. However, in contrast to Poaceae species, MLG in E. arvense consists mostly of cellotetraose rather than cellotetriose, and lacks long 1,4-beta-linked glucan blocks. Monosaccharide linkage analyses and immunochemical profiling indicated that, in E. arvense, MLG is a component of cell walls that have a novel architecture that differs significantly from that of the generally recognized type I and II cell walls. Unlike in type II walls, MLG in E. arvense does not appear to be co-extensive with glucuroarabinoxylans but occurs in walls that are rich in pectin. Immunofluorescence and immunogold localization showed that MLG occurs in both young and old regions of E. arvense stems, and is present in most cell types apart from cells in the vascular tissues. These findings have important implications for our understanding of cell-wall evolution, and also demonstrate that plant cell walls can be constructed in a way not previously envisaged.


Assuntos
Parede Celular/metabolismo , Equisetum/metabolismo , Poaceae/metabolismo , beta-Glucanas/metabolismo , Imunofluorescência , Espectrometria de Massas por Ionização e Dessorção a Laser Assistida por Matriz , beta-Glucanas/química
19.
New Phytol ; 184(1): 202-215, 2009.
Artigo em Inglês | MEDLINE | ID: mdl-19522841

RESUMO

Significant pressurized (convective) ventilation has been demonstrated in some flowering wetland plants, for example water-lilies and reeds, but not previously in nonflowering plants. Here we investigated convective flows in the great horsetail, Equisetum telmateia, and the possibility that convections aerated the massive rhizomes of the Calamites, extinct giant horsetails of the Carboniferous. Convection in E. telmateia was examined in relation to induction sites, anatomical pathways, relative humidity (RH), external wind-speed, diurnal effects, rhizome resistance and pressure-gradients. A mathematical model, incorporating Calamite aeration anatomy, was applied in assessing potentials for convective aeration. Individual shoots of E. telmateia generated extremely high rates of humidity-induced convection: < or = 120 cm(3) min(-1) (internal wind-velocity: 10 cm s(-1)) with rates proportional to branch numbers and 1/RH. Flows passed through branches, stem and rhizome via low-resistance lacunae (vallecular canals) and vented via stubble. Stomata supported internal pressures up to 800 Pa. Anatomically, E. telmateia resembles the Calamites and modelling predicted possible flows of 70 l min(-1) per Calamite tree. This is the first demonstration of significant convective flow in a nonflowering species, indicating that plant ventilation by a type of 'molecular gas-pump' may date back 350 million yr or more. Stomatal form and low-resistance pathways may facilitate high flow rates.


Assuntos
Equisetum/metabolismo , Extinção Biológica , Gases/metabolismo , Pressão , Ar , Equisetum/anatomia & histologia , Umidade , Modelos Biológicos , Brotos de Planta/anatomia & histologia , Estômatos de Plantas/fisiologia , Reologia , Fatores de Tempo , Vento
20.
New Phytol ; 179(1): 104-115, 2008.
Artigo em Inglês | MEDLINE | ID: mdl-18393951

RESUMO

Mixed-linkage (1-->3,1-->4)-beta-d-glucan (MLG) is a hemicellulose reputedly confined to certain Poales. Here, the taxonomic distribution of MLG, and xyloglucan, especially in early-diverging pteridophytes, has been re-investigated. Polysaccharides were digested with lichenase and xyloglucan endoglucanase (XEG), which specifically hydrolyse MLG and xyloglucan, respectively. The oligosaccharides produced were analysed by thin-layer chromatography (TLC), high-pressure liquid chromatography (HPLC) and alkaline peeling. Lichenase yielded oligo-beta-glucans from all Equisetum species tested (Equisetum arvense, Equisetum fluviatile, Equisetum scirpoides, Equisetum sylvaticum and Equisetum xtrachyodon). The major product was the tetrasaccharide beta-glucosyl-(1-->4)-beta-glucosyl-(1-->4)-beta-glucosyl-(1-->3)-glucose (G4G4G3G), which was converted to cellotriose by alkali, confirming its structure. Minor products included G3G, G4G3G and a nonasaccharide. By contrast, poalean MLGs yielded G4G3G > G4G4G3G > nonasaccharide > dodecasaccharide. No other pteridophytes tested contained MLG, including Psilotum and eusporangiate ferns. No MLG was found in lycopodiophytes, bryophytes, Chara or Nitella. XEG digestion showed that Equisetum xyloglucan has unusual repeat units. Equisetum, an exceedingly isolated genus whose closest living relatives diverged > 380 million years ago, has evolved MLG independently of the Poales. Equisetum and poalean MLGs share basic structural motifs but also exhibit clear-cut differences. Equisetum MLG is firmly wall-bound, and may tether neighbouring microfibrils. It is also suggested that MLG acts as a template for silica deposition, characteristic of grasses and horsetails.


Assuntos
Parede Celular/química , Equisetum/química , Polissacarídeos/fisiologia , beta-Glucanas/análise , Cromatografia Líquida de Alta Pressão , Cromatografia em Camada Fina , Equisetum/genética , Equisetum/metabolismo , Evolução Molecular , Glucanos/análise , Glucanos/fisiologia , Filogenia , Polissacarídeos/análise , Polissacarídeos/química , Hidróxido de Sódio/química , Xilanos/análise , beta-Glucanas/química , beta-Glucanas/metabolismo
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