Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 58
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
PLoS One ; 15(9): e0239677, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32986754

RESUMO

A geographically isolated maize landrace cultivated on nitrogen-depleted fields without synthetic fertilizer in the Sierra Mixe region of Oaxaca, Mexico utilizes nitrogen derived from the atmosphere and develops an extensive network of mucilage-secreting aerial roots that harbors a diazotrophic (N2-fixing) microbiota. Targeting these diazotrophs, we selected nearly 600 microbes of a collection obtained from mucilage and confirmed their ability to incorporate heavy nitrogen (15N2) metabolites in vitro. Sequencing their genomes and conducting comparative bioinformatic analyses showed that these genomes had substantial phylogenetic diversity. We examined each diazotroph genome for the presence of nif genes essential to nitrogen fixation (nifHDKENB) and carbohydrate utilization genes relevant to the mucilage polysaccharide digestion. These analyses identified diazotrophs that possessed the canonical nif gene operons, as well as many other operon configurations with concomitant fixation and release of >700 different 15N labeled metabolites. We further demonstrated that many diazotrophs possessed alternative nif gene operons and confirmed their genomic potential to derive chemical energy from mucilage polysaccharide to fuel nitrogen fixation. These results confirm that some diazotrophic bacteria associated with Sierra Mixe maize were capable of incorporating atmospheric nitrogen into their small molecule extracellular metabolites through multiple nif gene configurations while others were able to fix nitrogen without the canonical (nifHDKENB) genes.


Assuntos
Microbiota/genética , Fixação de Nitrogênio , Mucilagem Vegetal/metabolismo , Raízes de Plantas/microbiologia , Zea mays/microbiologia , Bactérias/genética , Bactérias/metabolismo , Genoma Bacteriano , México , Nitrogênio/metabolismo , Óperon , Filogenia , Raízes de Plantas/metabolismo , Sequenciamento Completo do Genoma
2.
Colloids Surf B Biointerfaces ; 184: 110489, 2019 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-31522025

RESUMO

Flaxseed protein (FP) and mucilage (FM) complex bioparticles as sustainable ingredients were assembled by electrostatic interaction for plant-based Pickering stabilization of flaxseed oil (FO)-in-water emulsions. The effect of FO content (1-5 wt%) on droplet size and accelerated creaming stability of the emulsions was evaluated, from which it was found that 2.5 wt% FO emulsion had the smallest initial droplet size (i.e. D[4,3] = 8 µm) and creaming velocity (2.9 µm/s). The microstructure of the emulsions was observed using Cryo-SEM, confocal and optical microscopy, showing a thick layer of the particles on the oil surface responsible for the stabilization. The physical stability of FO emulsions stabilized by complex bioparticles against various environmental stress conditions (pH, salt and temperature) was higher compared to plain FP- and polysorbate 80-stabilized emulsions. Thus, the droplet size of FP-stabilized emulsions (pH 3) increased from 21 to 38 µm after thermal treatment (80 °C), whereas the size distribution of particle-stabilized emulsions hardly changed. The latter emulsions also remained stable during 28 days of storage and displayed good stability against a wide range of pH conditions (2-9) and salt concentrations (0-500 mM) with no sign of oiling-off. The complex particles as Pickering emulsifiers were successful to depress the FO oxidation at 4 °C and 50 °C. This study could open a promising pathway for producing natural and surfactant-free emulsions through Pickering stabilization using plant-based biopolymer particles for protecting lipophilic bioactive components.


Assuntos
Emulsões/química , Linho/química , Óleo de Semente do Linho/química , Mucilagem Vegetal/química , Proteínas de Plantas/química , Tensoativos/química , Produtos Biológicos/química , Produtos Biológicos/metabolismo , Microscopia Crioeletrônica , Estabilidade de Medicamentos , Linho/metabolismo , Concentração de Íons de Hidrogênio , Microscopia Confocal , Oxirredução , Tamanho da Partícula , Mucilagem Vegetal/metabolismo , Proteínas de Plantas/metabolismo , Polissorbatos/química , Tensoativos/síntese química , Temperatura , Água/química
3.
Plant Mol Biol ; 101(4-5): 373-387, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31422517

RESUMO

KEY MESSAGE: Polysaccharide composition of seed mucilage was successfully modified using three seed coat-specific promoters driving expression of genes encoding cell wall-modifying enzymes. Arabidopsis thaliana seed coat epidermal cells synthesize and secrete large quantities of mucilage, a specialized secondary cell wall composed of cellulose, hemicellulose, and pectin. The composition and structure of mucilage confers its unique properties of expansion, extrusion, and adherence. We are developing seed mucilage as a model to study the biochemical and biological consequences of manipulating cell wall polysaccharides in vivo using cell wall-modifying enzymes. To specifically engineer mucilage composition and avoid altering other cell types, seed coat-specific promoters are required. In this study, we investigated the ability of seed coat-specific promoters from three genes, TESTA-ABUNDANT2 (TBA2), PEROXIDASE36 (PER36), and MUCILAGE-MODIFIED4 (MUM4), to express the cell wall modifying ß-galactosidase (BGAL)-encoding gene MUCILAGE-MODIFIED2 (MUM2) and complement the mum2 mutant. The strength of the three promoters relative to one another was found to vary by two to 250 fold, and correlated with their ability to rescue the mum2 mutant phenotype. The strongest of the three promoters, TBA2p, was then used to examine the ability of three MUM2 homologs to complement the mum2 extrusion and cell wall composition phenotypes. The degree of complementation was variable and correlated with the amino acid sequence similarity between the homologous gene products and MUM2. These data demonstrate that all three seed coat-specific promoters can drive expression of genes encoding carbohydrate-active enzymes in a spatial and temporal pattern sufficiently to modify polysaccharide composition in seed mucilage without obvious negative consequences to the rest of the plant.


Assuntos
Arabidopsis/genética , Parede Celular/metabolismo , Mucilagem Vegetal/metabolismo , Sequência de Aminoácidos , Arabidopsis/metabolismo , Parede Celular/química , Regulação da Expressão Gênica de Plantas , Filogenia , Mucilagem Vegetal/genética , Regiões Promotoras Genéticas , Domínios Proteicos , Sementes/genética , Sementes/metabolismo , Alinhamento de Sequência , Análise de Sequência de Proteína
4.
Chemosphere ; 233: 920-935, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31340420

RESUMO

The current study aimed to investigate the impacts of different concentrations of GO/PANI nanocomposites (25, 50 and 100 mg L-1), in comparison with GO and PANI, on seed germination behaviors, morpho-physiological and biochemical traits in intact (mucilaginous) and demucilaged seeds, and young seedlings of the medicinal plant Salvia mirzayanii. Upon exposure to GO, seed germination was delayed and reduced, and growth attributes (root and shoot length, shoot fresh weight, and total chlorophyll content) declined, all of which could be attributed to the reductions in water uptake and oxidative stress particularly in demucilaged seeds. A hormetic dose-dependent response was observed for the growth traits in both intact and demucilaged seedlings upon exposure to GO/PANI concentrations, i.e. low-concentration stimulation and high-concentration repression. Elevated levels of H2O2 in shoot tissue of the seedlings exposed to GO and high concentration of GO/PANI, in comparison with those exposed to low levels of GO/PANI and control, were linked with the activities of the antioxidant enzymes SOD, CAT, POD, and total phenolics. Overall, the results showed high toxicity of GO on germination and early growth of S. mirzayani that was more evident in demucilaged seedlings, whereas GO/PANI stimulated germination, and the effects on seedling growth were stimulatory or inhibitory depending on the application dose and presence of mucilage. Furthermore, the capacity of GO/PANI nanocomposites to improve germination and cause a regular porosity pattern in roots accompanied by improved water uptake and early establishment of S. mirzayanii propose potential implications of GO/PANI nanocomposites for seeds/plants in drought-prone ecosystems.


Assuntos
Compostos de Anilina/toxicidade , Antioxidantes/farmacologia , Germinação/efeitos dos fármacos , Grafite/toxicidade , Salvia/metabolismo , Plântula/crescimento & desenvolvimento , Sementes/efeitos dos fármacos , Catalase/metabolismo , Clorofila , Peróxido de Hidrogênio/farmacologia , Nanocompostos , Estresse Oxidativo/efeitos dos fármacos , Mucilagem Vegetal/metabolismo , Superóxido Dismutase/metabolismo , Água
5.
Plant Cell Physiol ; 60(6): 1296-1303, 2019 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-30892660

RESUMO

Plant roots secrete various substances with diverse functions against both plants and microbes in the rhizosphere. A major secretory substance is root-cap mucilage, whose functions have been well characterized, albeit mainly in crops. However, little is currently known about the developmental mechanisms of root-cap mucilage. Here, we show the accumulation and extrusion of root-cap mucilage in Arabidopsis. We found propidium iodide (PI) stainable structures between the plasma membrane and cell wall in the sixth layer of columella cells (c6) from the quiescent center. Ruthenium red staining and PI staining with calcium ions suggested that the structure comprises in part pectin polysaccharides. Electron microscopy revealed that the structure had a meshwork of electron-dense filaments that resembled periplasmic mucilage in other plants. In the c6 cells, we also observed many large vesicles with denser meshwork filaments to periplasmic mucilage, which likely mediate the transport of mucilage components. Extruded mucilage was observed outside a partially degraded cell wall in the c7 cells. Moreover, we found that the Class IIB NAC transcription factors BEARSKIN1 (BRN1) and BRN2, which are known to regulate the terminal differentiation of columella cells, were required for the efficient accumulation of root-cap mucilage in Arabidopsis. Taken together, our findings reveal the accumulation of and dynamic changes in periplasmic mucilage during columella cell development in Arabidopsis.


Assuntos
Arabidopsis/crescimento & desenvolvimento , Periplasma/metabolismo , Mucilagem Vegetal/metabolismo , Coifa/metabolismo , Arabidopsis/citologia , Arabidopsis/metabolismo , Arabidopsis/ultraestrutura , Corantes , Microscopia Eletrônica de Transmissão , Coifa/citologia , Coifa/ultraestrutura , Propídio
6.
Plant Physiol Biochem ; 139: 191-196, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-30904720

RESUMO

Pea (Pisum sativum) root cap releases a large number of living border cells that secrete abundant mucilage into the extracellular medium. Mucilage contains a complex mixture of polysaccharides, proteins and secondary metabolites important for its structure and function in defense. Unlike xyloglucan and cellulose, pectin and arabinogalactan proteins have been investigated in pea root and shown to be major components of border cell walls and mucilage. In this study, we investigated the occurrence of xyloglucan and cellulose in pea border cells and mucilage using cytochemical staining, immunocytochemistry and laser scanning confocal microscopy. Our data show that i) unlike cellulose, xyloglucan is highly present in the released mucilage as a dense fibrillary network enclosing border cells and ii) that xyloglucan and cellulose form molecular cross-bridges that tether cells and maintain them attached together. These findings suggest that secreted xyloglucan is essential for mucilage strengthening and border cell attachment and functioning.


Assuntos
Celulose/metabolismo , Glucanos/metabolismo , Ervilhas/metabolismo , Raízes de Plantas/citologia , Xilanos/metabolismo , Microscopia Confocal , Ervilhas/ultraestrutura , Mucilagem Vegetal/metabolismo , Coifa/citologia , Coifa/metabolismo , Raízes de Plantas/metabolismo , Raízes de Plantas/ultraestrutura
7.
Plant Mol Biol ; 99(4-5): 421-436, 2019 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-30707395

RESUMO

KEY MESSAGE: A possible transcription factor TLP2 was identified to be involved in the regulation of HG biosynthesis in Arabidopsis seed mucilage. TLP2 can translocate into nucleus from plasma membrane by interacting with NF-YC3. The discovery of TLP2 gene function can further fulfill the regulatory network of pectin biosynthesis in Arabidopsis thaliana. Arabidopsis seed coat mucilage is an excellent model system to study the biosynthesis, function and regulation of pectin. Rhamnogalacturonan I (RG-I) and homogalacturonan (HG) are the major polysaccharides constituent of the Arabidopsis seed coat mucilage. Here, we identified a Tubby-like gene, Tubby-like protein 2 (TLP2), which was up-regulated in developing siliques when mucilage began to be produced. Ruthenium red (RR) staining of the seeds showed defective mucilage of tlp2-1 mutant after vigorous shaking compared to wild type (WT). Monosaccharide composition analysis revealed that the amount of total sugars and galacturonic acid (GalA) decreased significantly in the adherent mucilage (AM) of tlp2-1 mutant. Immunolabelling and dot immunoblotting analysis showed that unesterified HG decreased in the tlp2-1 mutant. Furthermore, TLP2 can translocate into nucleus by interacting with Nuclear Factor Y subunit C3 (NF-YC3) to function as a transcription factor. RNA-sequence and transactivation assays revealed that TLP2 could activate UDP-glucose 4-epimerase 1 (UGE1). In all, it is concluded that TLP2 could regulate the biosynthesis of HG possibly through the positive activation of UGE1.


Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/metabolismo , Pectinas/biossíntese , Mucilagem Vegetal/metabolismo , Sementes/metabolismo , Arabidopsis/genética , Proteínas de Arabidopsis/genética , Proteínas F-Box/genética , Proteínas F-Box/metabolismo , Regulação da Expressão Gênica de Plantas , Ácidos Hexurônicos , Mutação , Fenótipo , Plantas Geneticamente Modificadas , Polissacarídeos , Sementes/crescimento & desenvolvimento , Análise de Sequência de RNA , Fatores de Transcrição , Ativação Transcricional , Uridina Difosfato Glucose Desidrogenase/metabolismo
8.
Mol Plant ; 12(1): 99-112, 2019 01 07.
Artigo em Inglês | MEDLINE | ID: mdl-30503864

RESUMO

Seed exudates influence the behavior of soil organisms, but how this occurs remains unclear, particularly for multicellular animals. Here we show that compounds associated with Arabidopsis seed-coat mucilage regulate the behavior of soil-borne animals, specifically root-knot nematodes (RKNs). Infective RKN J2 larvae actively travel toward Arabidopsis seeds through chemotaxis. Analysis of Arabidopsis mucilage mutants demonstrated that the attraction of RKNs to Arabidopsis seeds requires the synthesis and extrusion of seed-coat mucilage. Extracted mucilage alone is not sufficient to attract RKNs, but seed-surface carbohydrates and proteins are required for this process. These findings suggest that the RKN chemoattractant is synthesized de novo upon mucilage extrusion but may be highly unstable. RKNs attracted by this mucilage-dependent mechanism can infect the emerging seedling. However, the attraction signal from seedling roots likely acts independently of the seed-coat signal and may mask the attraction to seed-coat mucilage after germination. Multiple RKN species are attracted by Arabidopsis seeds, suggesting that this mechanism is conserved in RKNs. These findings indicate that seed exudate can regulate the behavior of multicellular animals and highlight the potential roles of seed-coat mucilage in biotic interactions with soil microorganisms.


Assuntos
Arabidopsis/parasitologia , Nematoides/fisiologia , Exsudatos de Plantas/metabolismo , Mucilagem Vegetal/metabolismo , Sementes/metabolismo , Animais , Arabidopsis/química , Arabidopsis/metabolismo , Comportamento Animal , Quimiotaxia , Exsudatos de Plantas/química , Mucilagem Vegetal/química , Sementes/parasitologia
9.
New Phytol ; 221(2): 881-895, 2019 01.
Artigo em Inglês | MEDLINE | ID: mdl-30277578

RESUMO

The differentiation of the seed coat epidermal (SCE) cells in Arabidopsis thaliana leads to the production of a large amount of pectin-rich mucilage and a thick cellulosic secondary cell wall. The mechanisms by which cortical microtubules are involved in the formation of these pectinaceous and cellulosic cell walls are still largely unknown. Using a reverse genetic approach, we found that TONNEAU1 (TON1) recruiting motif 4 (TRM4) is implicated in cortical microtubule organization in SCE cells, and functions as a novel player in the establishment of mucilage structure. TRM4 is preferentially accumulated in the SCE cells at the stage of mucilage biosynthesis. The loss of TRM4 results in compact seed mucilage capsules, aberrant mucilage cellulosic structure, short cellulosic rays and disorganized cellulose microfibrils in mucilage. The defects could be rescued by transgene complementation of trm4 alleles. Probably, this is a consequence of a disrupted organization of cortical microtubules, observed using fluorescently tagged tubulin proteins in trm4 SCE cells. Furthermore, TRM4 proteins co-aligned with microtubules and interacted directly with CELLULOSE SYNTHASE 3 in two independent assays. Together, the results indicate that TRM4 is essential for microtubule array organization and therefore correct cellulose orientation in the SCE cells, as well as the establishment of the subsequent mucilage architecture.


Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/genética , Celulose/metabolismo , Glucosiltransferases/metabolismo , Proteínas Associadas aos Microtúbulos/metabolismo , Alelos , Arabidopsis/fisiologia , Arabidopsis/ultraestrutura , Proteínas de Arabidopsis/genética , Parede Celular/metabolismo , Parede Celular/ultraestrutura , Glucosiltransferases/genética , Proteínas Associadas aos Microtúbulos/genética , Microtúbulos/metabolismo , Microtúbulos/ultraestrutura , Pectinas/metabolismo , Mucilagem Vegetal/metabolismo , Sementes/genética , Sementes/fisiologia , Sementes/ultraestrutura
10.
Plant Cell Environ ; 42(2): 591-605, 2019 02.
Artigo em Inglês | MEDLINE | ID: mdl-30193400

RESUMO

Seedling emergence is a critical stage in the establishment of desert plants. Soil microbes participate in plant growth and development, but information is lacking with regard to the role of microbes on seedling emergence. We applied the biocides (captan and streptomycin) to assess how seed mucilage interacts with soil microbial community and physiochemical processes to affect seedling emergence of Artemisia sphaerocephala on the desert sand dune. Fungal and bacterial community composition and diversity and fungal-bacterial interactions were changed by both captan and streptomycin. Mucilage increased soil enzyme activities and fungal-bacterial interactions. Highest seedling emergence occurred under streptomycin and mucilage treatment. Members of the phyla Firmicutes and Glomeromycota were the keystone species that improved A. sphaerocephala seedling emergence, by increasing resistance of young seedlings to drought and pathogen. Seed mucilage directly improved seedling emergence and indirectly interacted with the soil microbial community through strengthening fungal-bacterial interactions and providing favourable environment for soil enzymes to affect seedling emergence. Our study provides a comprehensive understanding of the regulatory mechanisms by which soil microbial community and seed mucilage interactively promote successful establishment of populations of desert plants on the barren and stressful sand dune.


Assuntos
Interações entre Hospedeiro e Microrganismos , Mucilagem Vegetal/fisiologia , Plântula/crescimento & desenvolvimento , Sementes/fisiologia , Microbiologia do Solo , Anti-Infecciosos/farmacologia , Artemisia/crescimento & desenvolvimento , Artemisia/metabolismo , Artemisia/microbiologia , Captana/farmacologia , Clima Desértico , Sequenciamento de Nucleotídeos em Larga Escala , Interações entre Hospedeiro e Microrganismos/fisiologia , Mucilagem Vegetal/metabolismo , RNA Ribossômico 16S/genética , Plântula/metabolismo , Plântula/microbiologia , Sementes/metabolismo , Sementes/microbiologia , Estreptomicina/farmacologia
11.
J Sci Food Agric ; 99(6): 2883-2891, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-30460676

RESUMO

BACKGROUND: Among Cactaceae, the genus Opuntia is widely known for the use of its biomass as cattle fodder and in human nutrition (e.g. species such as Opuntia ficus indica and Opuntia streptacantha). In particular, O. streptacantha (OS) produces abundant mucilage and, hence, the characterization of its properties and nutritional value is important. Accordingly, determination of the dietary fiber content of the OS mucilage and the fermentability of its hydrolysis products (oligosaccharides, OLI) is important for developing new uses of the crop as a functional food. RESULTS: The values for insoluble dietary fiber and soluble dietary fiber in the mucilage were 204.6 and 371.6 g kg-1 , respectively. After hydrolysis of OS mucilage with α-amylase, three purified fractions of OLI were evaluated (OLI-A, OLI-B and OLI-C). OLI (1% w/v) stimulated the growth of the commercial probiotic strains (Lactobacillus acidophilus, Lactobacillus casei and Bifidobacterium animalis subsp. lactis) in vitro, showing behaviors similar to those of commercial inulin. The production of short chain fatty acids (SCFAs) in the fermentation broth was also determined. The final pH of the fermentation broth as well as the identification and concentrations of SCFA depended on the type of OLI and probiotic used. CONCLUSION: The OS mucilage is an unconventional fiber source and can be used to produce non-digestible OLI as functional compounds. This knowledge will be useful for proposing new sustainable ways of processing cacti crops for food and industrial purposes. © 2018 Society of Chemical Industry.


Assuntos
Oligossacarídeos/química , Opuntia/química , Mucilagem Vegetal/química , alfa-Amilases/química , Bifidobacterium animalis/metabolismo , Biocatálise , Fibras na Dieta/análise , Fibras na Dieta/metabolismo , Ácidos Graxos Voláteis/metabolismo , Hidrólise , Lactobacillus acidophilus/metabolismo , Modelos Biológicos , Valor Nutritivo , Oligossacarídeos/metabolismo , Opuntia/metabolismo , Mucilagem Vegetal/metabolismo , Polissacarídeos/química , Polissacarídeos/metabolismo , alfa-Amilases/metabolismo
12.
PLoS One ; 13(9): e0204525, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-30256843

RESUMO

An indigenous maize landrace from the Sierra Mixe region of Oaxaca, Mexico exhibits extensive formation of aerial roots which exude large volumes of a polysaccharide-rich gel matrix or "mucilage" that harbors diazotrophic microbiota. We hypothesize that the mucilage associated microbial community carries out multiple functions, including disassembly of the mucilage polysaccharide. In situ, hydrolytic assay of the mucilage revealed endogenous arabinofuranosidase, galactosidase, fucosidase, mannosidase and xylanase activities. Screening the mucilage against plant cell wall glycan-specific monoclonal antibodies recognized the presence of carbohydrate epitopes of hemicellulosic polysaccharides like xyloglucan (both non-fucosylated and fucosylated), xylan (both substituted and unsubstituted xylan domains) and pectic-arabinogalactans, all of which are potential carbon sources for mucilage microbial residents. Mucilage metagenome annotation using MG-RAST identified the members forming the microbial community, and gene fragments with predicted functions associated with carbohydrate disassembly. Data from the in situ hydrolytic activity and monoclonal antibody screening assays were used to guide the selection of five full length genes with predicted glycosyl hydrolase function from the GenBank database that were similar to gene fragments of high relative abundance in the mucilage metagenomes. These five genes were then synthesized for recombinant production in Escherichia coli. Here we report the characterization of an α-N-arabinofuranosidase (GH51) and an oligosaccharide reducing-end xylanase (GH8) from Flavobacterium johnsoniae; an α-L-fucosidase (GH29) and a xylan ß-1,4 xylosidase (GH39) from Spirosoma linguale, and a ß-mannosidase (GH2) from Agrobacterium fabrum. Biochemical characterization of these enzymes revealed a ß-Mannosidase that also exhibits a secondary activity towards the cleavage of galactosyl residues. We also describe two xylanases (GH8 and GH39) from underexplored glycosyl hydrolase families, one thermostable α-L-Fucosidase (GH29) and a thermostable α-N-Arabinofuranosidase (GH51).


Assuntos
Glicosídeo Hidrolases/genética , Glicosídeo Hidrolases/metabolismo , Zea mays/enzimologia , Zea mays/microbiologia , Anticorpos Monoclonais , Proteínas de Bactérias/química , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Parede Celular/metabolismo , Glicosídeo Hidrolases/química , Metagenoma , Microbiota/genética , Filogenia , Componentes Aéreos da Planta/enzimologia , Componentes Aéreos da Planta/microbiologia , Mucilagem Vegetal/química , Mucilagem Vegetal/metabolismo , Polissacarídeos/imunologia , Polissacarídeos/metabolismo , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo
13.
Plant Physiol ; 178(3): 1045-1064, 2018 11.
Artigo em Inglês | MEDLINE | ID: mdl-30228108

RESUMO

Pectin is a vital component of the plant cell wall and provides the molecular glue that maintains cell-cell adhesion, among other functions. As the most complex wall polysaccharide, pectin is composed of several covalently linked domains, such as homogalacturonan (HG) and rhamnogalacturonan I (RG I). Pectin has widespread uses in the food industry and has emerging biomedical applications, but its synthesis remains poorly understood. For instance, the enzymes that catalyze RG I elongation remain unknown. Recently, a coexpression- and sequence-based MUCILAGE-RELATED (MUCI) reverse genetic screen uncovered hemicellulose biosynthetic enzymes in the Arabidopsis (Arabidopsis thaliana) seed coat. Here, we use an extension of this strategy to identify MUCI70 as the founding member of a glycosyltransferase family essential for the accumulation of seed mucilage, a gelatinous wall rich in unbranched RG I. Detailed biochemical and histological characterization of two muci70 mutants and two galacturonosyltransferase11 (gaut11) mutants identified MUCI70 and GAUT11 as required for two distinct RG I domains in seed mucilage. We demonstrate that, unlike MUCI70, GAUT11 catalyzes HG elongation in vitro and, thus, likely is required for the synthesis of an HG region important for RG I elongation. Analysis of a muci70 gaut11 double mutant confirmed that MUCI70 and GAUT11 are indispensable for the production and release of the bulk of mucilage RG I and for shaping the surface morphology of seeds. In addition, we uncover relationships between pectin and hemicelluloses and show that xylan is essential for the elongation of at least one RG I domain.


Assuntos
Proteínas de Arabidopsis/fisiologia , Arabidopsis/enzimologia , Glucuronosiltransferase/metabolismo , Hidrolases/fisiologia , Pectinas/metabolismo , Mucilagem Vegetal/metabolismo , Sementes/enzimologia , Arabidopsis/genética , Arabidopsis/ultraestrutura , Proteínas de Arabidopsis/genética , Parede Celular/metabolismo , Parede Celular/ultraestrutura , Glucuronosiltransferase/genética , Glicosiltransferases/genética , Glicosiltransferases/metabolismo , Hidrolases/genética , Microscopia Eletrônica de Varredura , Filogenia , Mucilagem Vegetal/química , Mucilagem Vegetal/ultraestrutura , Polissacarídeos/metabolismo , Sementes/genética , Sementes/ultraestrutura
14.
Plant Physiol ; 178(3): 1011-1026, 2018 11.
Artigo em Inglês | MEDLINE | ID: mdl-30185440

RESUMO

The interaction between mannan polysaccharides and cellulose microfibrils contributes to cell wall properties in some vascular plants, but the molecular arrangement of mannan in the cell wall and the nature of the molecular bonding between mannan and cellulose remain unknown. Previous studies have shown that mannan is important in maintaining Arabidopsis (Arabidopsis thaliana) seed mucilage architecture, and that Cellulose Synthase-Like A2 (CSLA2) synthesizes a glucomannan backbone, which Mannan α-Galactosyl Transferase1 (MAGT1/GlycosylTransferase-Like6/Mucilage Related10) might decorate with single α-Gal branches. Here, we investigated the ratio and sequence of Man and Glc and the arrangement of Gal residues in Arabidopsis mucilage mannan using enzyme sequential digestion, carbohydrate gel electrophoresis, and mass spectrometry. We found that seed mucilage galactoglucomannan has a backbone consisting of the repeating disaccharide [4)-ß-Glc-(1,4)-ß-Man-(1,], and most of the Man residues in the backbone are substituted by single α-1,6-Gal. CSLA2 is responsible for the synthesis of this patterned glucomannan backbone and MAGT1 catalyses the addition of α-Gal. In vitro activity assays revealed that MAGT1 transferred α-Gal from UDP-Gal only to Man residues within the CSLA2 patterned glucomannan backbone acceptor. These results indicate that CSLAs and galactosyltransferases are able to make precisely defined galactoglucomannan structures. Molecular dynamics simulations suggested this patterned galactoglucomannan is able to bind stably to some hydrophilic faces and to hydrophobic faces of cellulose microfibrils. A specialization of the biosynthetic machinery to make galactoglucomannan with a patterned structure may therefore regulate the mode of binding of this hemicellulose to cellulose fibrils.


Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/enzimologia , Celulose/metabolismo , Galactosiltransferases/metabolismo , Glucosiltransferases/metabolismo , Glicosiltransferases/metabolismo , Mananas/química , Arabidopsis/química , Arabidopsis/genética , Proteínas de Arabidopsis/genética , Parede Celular/metabolismo , Galactosiltransferases/genética , Glucosiltransferases/genética , Glicosiltransferases/genética , Mananas/metabolismo , Mucilagem Vegetal/química , Mucilagem Vegetal/metabolismo , Polissacarídeos/metabolismo , Sementes/química , Sementes/enzimologia , Sementes/genética
15.
Plant Cell Physiol ; 59(11): 2331-2338, 2018 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-30099531

RESUMO

The adaptor protein (AP) complexes play crucial roles in vesicle formation in post-Golgi trafficking. Land plants have five types of AP complexes (AP-1 to AP-5), each of which consists of two large subunits, one medium subunit and one small subunit. Here, we show that the Arabidopsis AP-1 complex mediates the polarized secretion and accumulation of a pectic polysaccharide called mucilage in seed coat cells. Previously, a loss-of-function mutant of AP1M2, the medium subunit of AP-1, has been shown to display deleterious growth defects because of defective cytokinesis. To investigate the function of AP-1 in interphase, we generated transgenic Arabidopsis plants expressing AP1M2-GFP (green fluorescent protein) under the control of the cytokinesis-specific KNOLLE (KN) promoter in the ap1m2 background. These transgenic plants, designated pKN lines, successfully rescued the cytokinesis defect and dwarf phenotype of ap1m2. pKN lines showed reduced mucilage extrusion from the seed coat. Furthermore, abnormal accumulation of mucilage was found in the vacuoles of the outermost integument cells of pKN lines. During seed development, the accumulation of AP1M2-GFP was greatly reduced in the integument cells of pKN lines. These results suggest that trans-Golgi network (TGN)-localized AP-1 is involved in the trafficking of mucilage components to the outer surface of seed coat cells. Our study highlights an evolutionarily conserved function of AP-1 in polarized sorting in eukaryotic cells.


Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/metabolismo , Mucilagem Vegetal/biossíntese , Sementes/metabolismo , Fator de Transcrição AP-1/metabolismo , Regulação da Expressão Gênica de Plantas , Mucilagem Vegetal/metabolismo , Regiões Promotoras Genéticas , Rede trans-Golgi/metabolismo
16.
PLoS Biol ; 16(8): e2006352, 2018 08.
Artigo em Inglês | MEDLINE | ID: mdl-30086128

RESUMO

Plants are associated with a complex microbiota that contributes to nutrient acquisition, plant growth, and plant defense. Nitrogen-fixing microbial associations are efficient and well characterized in legumes but are limited in cereals, including maize. We studied an indigenous landrace of maize grown in nitrogen-depleted soils in the Sierra Mixe region of Oaxaca, Mexico. This landrace is characterized by the extensive development of aerial roots that secrete a carbohydrate-rich mucilage. Analysis of the mucilage microbiota indicated that it was enriched in taxa for which many known species are diazotrophic, was enriched for homologs of genes encoding nitrogenase subunits, and harbored active nitrogenase activity as assessed by acetylene reduction and 15N2 incorporation assays. Field experiments in Sierra Mixe using 15N natural abundance or 15N-enrichment assessments over 5 years indicated that atmospheric nitrogen fixation contributed 29%-82% of the nitrogen nutrition of Sierra Mixe maize.


Assuntos
Microbiota/genética , Fixação de Nitrogênio/fisiologia , Nitrogênio/metabolismo , Zea mays/metabolismo , México , Microbiota/fisiologia , Filogenia , Desenvolvimento Vegetal , Mucilagem Vegetal/metabolismo , Raízes de Plantas/metabolismo , Polissacarídeos/metabolismo , Solo , Microbiologia do Solo
17.
Plant Sci ; 272: 179-192, 2018 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-29807590

RESUMO

A polysaccharide-rich mucilage is released from the seed coat epidermis of numerous plant species and has been intensively studied in the model plant Arabidopsis. This has led to the identification of a large number of genes involved in the synthesis, secretion and modification of cell wall polysaccharides such as pectin, hemicellulose and cellulose being identified. These genes include a small network of transcription factors (TFs) and transcriptional co-regulators, that not only regulate mucilage production, but epidermal cell differentiation and in some cases flavonoid biosynthesis in the internal endothelial layer of the seed coat. Here we focus on the function of these regulators and propose a simplified model where they are assigned to a hierarchical gene network with three regulatory levels (tiers) as a means of assisting in the interpretation of the complexity. We discuss limitations of current methodologies and highlight some of the problems associated with defining the function of TFs, particularly those that perform different functions in adjacent layers of the seed coat. We suggest approaches that should provide a more accurate picture of the function of transcription factors involved with mucilage production and release.


Assuntos
Arabidopsis/metabolismo , Mucilagem Vegetal/metabolismo , Sementes/metabolismo , Fatores de Transcrição/fisiologia , Regulação da Expressão Gênica de Plantas/fisiologia
18.
Plant Physiol ; 176(4): 2737-2749, 2018 04.
Artigo em Inglês | MEDLINE | ID: mdl-29440562

RESUMO

Pectin, which is a major component of the plant primary cell walls, is synthesized and methyl-esterified in the Golgi apparatus and then demethylesterified by pectin methylesterases (PMEs) located in the cell wall. The degree of methylesterification affects the functional properties of pectin, and thereby influences plant growth, development and defense. However, little is known about the mechanisms that regulate pectin demethylesterification. Here, we show that in Arabidopsis (Arabidopsis thaliana) seed coat mucilage, the absence of the MYB52 transcription factor is correlated with an increase in PME activity and a decrease in the degree of pectin methylesterification. Decreased methylesterification in the myb52 mutant is also correlated with an increase in the calcium content of the seed mucilage. Chromatin immunoprecipitation analysis and molecular genetic studies suggest that MYB52 transcriptionally activates PECTIN METHYLESTERASE INHIBITOR6 (PMEI6), PMEI14, and SUBTILISIN-LIKE SER PROTEASE1.7 (SBT1.7) by binding to their promoters. PMEI6 and SBT1.7 have previously been shown to be involved in seed coat mucilage demethylesterification. Our characterization of two PMEI14 mutants suggests that PMEI14 has a role in seed coat mucilage demethylesterification, although its activity may be confined to the seed coat in contrast to PMEI6, which functions in the whole seed. Our demonstration that MYB52 negatively regulates pectin demethylesterification in seed coat mucilage, and the identification of components of the molecular network involved, provides new insight into the regulatory mechanism controlling pectin demethylesterification and increases our understanding of the transcriptional regulation network involved in seed coat mucilage formation.


Assuntos
Proteínas de Arabidopsis/metabolismo , Pectinas/metabolismo , Mucilagem Vegetal/metabolismo , Sementes/metabolismo , Arabidopsis/genética , Arabidopsis/metabolismo , Proteínas de Arabidopsis/genética , Cálcio/metabolismo , Hidrolases de Éster Carboxílico/genética , Hidrolases de Éster Carboxílico/metabolismo , Parede Celular/enzimologia , Parede Celular/genética , Esterificação , Regulação da Expressão Gênica de Plantas , Redes Reguladoras de Genes , Mutação , Regiões Promotoras Genéticas/genética , Ligação Proteica , Sementes/genética
19.
Plant J ; 94(3): 497-512, 2018 05.
Artigo em Inglês | MEDLINE | ID: mdl-29446495

RESUMO

The production of hydrophilic mucilage along the course of seed coat epidermal cell differentiation is a common adaptation in angiosperms. Previous studies have identified COBRA-LIKE 2 (COBL2), a member of the COBRA-LIKE gene family, as a novel component required for crystalline cellulose deposition in seed coat epidermal cells. In recent years, Arabidopsis seed coat epidermal cells (SCEs), also called mucilage secretory cells, have emerged as a powerful model system for the study of plant cell wall components biosynthesis, secretion, assembly and de muro modification. Despite accumulating data, the molecular mechanism of COBL function remains largely unknown. In the current research, we utilized genetic interactions to study the role of COBL2 as part of the protein network required for seed mucilage production. Using correlative phenotyping of structural and biochemical characteristics, unique features of the cobl2 extruded mucilage are revealed, including: 'unraveled' ray morphology, loss of primary cell wall 'pyramidal' organization, reduced Ruthenium red staining intensity of the adherent mucilage layer, and increased levels of the monosaccharides arabinose and galactose. Examination of the cobl2cesa5 double mutant provides insight into the interface between COBL function and cellulose deposition. Additionally, genetic interactions between cobl2 and fei1fei2 as well as between each of these mutants to mucilage-modified 2 (mum2) suggest that COBL2 functions independently of the FEI-SOS pathway. Altogether, the presented data place COBL2 within the complex protein network required for cell wall deposition in the context of seed mucilage and introduce new methodology expending the seed mucilage phenotyping toolbox.


Assuntos
Proteínas de Arabidopsis/fisiologia , Arabidopsis/metabolismo , Proteínas de Membrana/fisiologia , Mucilagem Vegetal/metabolismo , Polissacarídeos/metabolismo , Sementes/metabolismo , Proteínas de Arabidopsis/metabolismo , Celulose/metabolismo , Glucosiltransferases/metabolismo , Proteínas de Membrana/metabolismo , Fenótipo , Epiderme Vegetal/metabolismo
20.
Plant Cell Rep ; 37(4): 565-574, 2018 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-29188422

RESUMO

Climbing plants have unique adaptations to enable them to compete for sunlight, for which they invest minimal resources for vertical growth. Indeed, their stems bear relatively little weight, as they traverse their host substrates skyward. Climbers possess high tensile strength and flexibility, which allows them to utilize natural and manmade structures for support and growth. The climbing strategies of plants have intrigued scientists for centuries, yet our understanding about biochemical adaptations and their molecular undergirding is still in the early stages of research. Nonetheless, recent discoveries are promising, not only from a basic knowledge perspective, but also for bioinspired product development. Several adaptations, including nanoparticle and adhesive production will be reviewed, as well as practical translation of these adaptations to commercial applications. We will review the botanical literature on the modes of adaptation to climb, as well as specialized organs-and cellular innovations. Finally, recent molecular and biochemical data will be reviewed to assess the future needs and new directions for potential practical products that may be bioinspired by climbing plants.


Assuntos
Adaptação Fisiológica/fisiologia , Cálcio/metabolismo , Glicosaminoglicanos/metabolismo , Plantas/metabolismo , Luz Solar , Fenômenos Biomecânicos , Modelos Biológicos , Folhas de Planta/metabolismo , Folhas de Planta/fisiologia , Mucilagem Vegetal/metabolismo , Plantas/classificação , Tricomas/fisiologia
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA