Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 12 de 12
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
Methods Mol Biol ; 2722: 117-127, 2024.
Artigo em Inglês | MEDLINE | ID: mdl-37897604

RESUMO

Plant vascular pathogens use different ways to reach the xylem vessels and cause devastating diseases in plants. Resistant and tolerant plants have evolved various defense mechanisms against vascular pathogens. Inducible physico-chemical structures, such as the formation of tyloses and wall reinforcements with phenolic polymers, are very effective barriers that confine the pathogen and prevent colonization. Here, we use a combination of classical histochemistry along with bright-field and fluorescence microscopy and two-dimensional nuclear magnetic resonance (2D-NMR) spectroscopy to visualize and characterize wall reinforcements containing phenolic wall polymers, namely, lignin, ferulates, and suberin, which occur in different xylem vasculature in response to pathogen attack.


Assuntos
Lignina , Lipídeos , Lignina/análise , Lipídeos/análise , Plantas , Xilema/química , Parede Celular
3.
New Phytol ; 234(4): 1411-1429, 2022 05.
Artigo em Inglês | MEDLINE | ID: mdl-35152435

RESUMO

Tomato varieties resistant to the bacterial wilt pathogen Ralstonia solanacearum have the ability to restrict bacterial movement in the plant. Inducible vascular cell wall reinforcements seem to play a key role in confining R. solanacearum into the xylem vasculature of resistant tomato. However, the type of compounds involved in such vascular physico-chemical barriers remain understudied, while being a key component of resistance. Here we use a combination of histological and live-imaging techniques, together with spectroscopy and gene expression analysis to understand the nature of R. solanacearum-induced formation of vascular coatings in resistant tomato. We describe that resistant tomato specifically responds to infection by assembling a vascular structural barrier formed by a ligno-suberin coating and tyramine-derived hydroxycinnamic acid amides. Further, we show that overexpressing genes of the ligno-suberin pathway in a commercial susceptible variety of tomato restricts R. solanacearum movement inside the plant and slows disease progression, enhancing resistance to the pathogen. We propose that the induced barrier in resistant plants does not only restrict the movement of the pathogen, but may also prevent cell wall degradation by the pathogen and confer anti-microbial properties, effectively contributing to resistance.


Assuntos
Ralstonia solanacearum , Solanum lycopersicum , Amidas/metabolismo , Ácidos Cumáricos/metabolismo , Solanum lycopersicum/microbiologia , Doenças das Plantas/microbiologia , Tiramina/metabolismo , Virulência
4.
J Exp Bot ; 72(2): 184-198, 2021 02 02.
Artigo em Inglês | MEDLINE | ID: mdl-32976552

RESUMO

Xylem vascular wilt pathogens cause devastating diseases in plants. Proliferation of these pathogens in the xylem causes massive disruption of water and mineral transport, resulting in severe wilting and death of the infected plants. Upon reaching the xylem vascular tissue, these pathogens multiply profusely, spreading vertically within the xylem sap, and horizontally between vessels and to the surrounding tissues. Plant resistance to these pathogens is very complex. One of the most effective defense responses in resistant plants is the formation of physico-chemical barriers in the xylem tissue. Vertical spread within the vessel lumen is restricted by structural barriers, namely, tyloses and gels. Horizontal spread to the apoplast and surrounding healthy vessels and tissues is prevented by vascular coating of the colonized vessels with lignin and suberin. Both vertical and horizontal barriers compartmentalize the pathogen at the infection site and contribute to their elimination. Induction of these defenses are tightly coordinated, both temporally and spatially, to avoid detrimental consequences such as cavitation and embolism. We discuss current knowledge on mechanisms underlying plant-inducible structural barriers against major xylem-colonizing pathogens. This knowledge may be applied to engineer metabolic pathways of vascular coating compounds in specific cells, to produce plants resistant towards xylem colonizers.


Assuntos
Doenças das Plantas , Solanum lycopersicum , Xilema
5.
ACS Biomater Sci Eng ; 5(2): 413-419, 2019 Feb 11.
Artigo em Inglês | MEDLINE | ID: mdl-33405806

RESUMO

Efficacy and efficiency of pesticide application in the field through the foliage still face many challenges. There exists a mismatch between the hydrophobic character of the leaf and the active molecule, low dispersion of the pesticides on the leaves' surface, runoff loss, and rolling down of the active molecules to the field, decreasing their efficacy and increasing their accumulation to the soil. We produced bacterial cellulose-silver nanoparticles (BC-AgNPs) hybrid patches by in situ thermal reduction under microwave irradiation in a scalable manner and obtaining AgNPs strongly anchored to the BC. Those hybrids increase the interaction of the pesticide (AgNPs) with the foliage and avoids runoff loss and rolling down of the nanoparticles. The positive antibacterial and antifungal properties were assessed in vitro against the bacteria Escherichia coli and two agro-economically relevant pathogens: the bacterium Pseudomonas syringae and the fungus Botrytis cinerea. We showed in vivo inhibition of the infection in Nicotiana benthamiana and tomato leaves, as proven by the suppression of the expression of defense molecular markers and reactive oxygen species production. The hydrogel-like character of the bacterial cellulose matrix increases the adherence to the foliage of the patches.

6.
Plant Sci ; 236: 272-82, 2015 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-26025540

RESUMO

Coumarate 3-hydroxylase (C3H) catalyzes a key step of the synthesis of the two main lignin subunits, guaiacyl (G) and syringyl (S) in dicotyledonous species. As no functional data are available in regards to this enzyme in monocotyledonous species, we generated C3H1 knock-down maize plants. The results obtained indicate that C3H1 participates in lignin biosynthesis as its down-regulation redirects the phenylpropanoid flux: as a result, increased amounts of p-hydroxyphenyl (H) units, lignin-associated ferulates and the flavone tricin were detected in transgenic stems cell walls. Altogether, these changes make stem cell walls more degradable in the most C3H1-repressed plants, despite their unaltered polysaccharide content. The increase in H monomers is moderate compared to C3H deficient Arabidopsis and alfalfa plants. This could be due to the existence of a second maize C3H protein (C3H2) that can compensate the reduced levels of C3H1 in these C3H1-RNAi maize plants. The reduced expression of C3H1 alters the macroscopic phenotype of the plants, whose growth is inhibited proportionally to the extent of C3H1 repression. Finally, the down-regulation of C3H1 also increases the synthesis of flavonoids, leading to the accumulation of anthocyanins in transgenic leaves.


Assuntos
Regulação para Baixo , Oxigenases de Função Mista/genética , Proteínas de Plantas/genética , Zea mays/genética , Antocianinas/metabolismo , Parede Celular/metabolismo , Ácidos Cumáricos/metabolismo , Lignina/metabolismo , Oxigenases de Função Mista/metabolismo , Proteínas de Plantas/metabolismo , Plantas Geneticamente Modificadas/genética , Plantas Geneticamente Modificadas/metabolismo , Interferência de RNA , Zea mays/metabolismo
7.
J Plant Physiol ; 170(9): 864-73, 2013 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-23384757

RESUMO

Late Embryogenesis Abundant (LEA) proteins participate in plant stress responses and contribute to the acquisition of desiccation tolerance. In this report Rab28 LEA gene has been over-expressed in maize plants under a constitutive maize promoter. The expression of Rab28 transcripts led to the accumulation and stability of Rab28 protein in the transgenic plants. Native Rab28 protein is localized to nucleoli in wild type maize embryo cells; here we find by whole-mount immunocytochemistry that in root cells of Rab28 transgenic and wild-type plants the protein is also associated to nucleolar structures. Transgenic plants were tested for stress tolerance and resulted in sustained growth under polyethyleneglycol (PEG)-mediated dehydration compared to wild-type controls. Under osmotic stress transgenic seedlings showed increased leaf and root areas, higher relative water content (RWC), reduced chlorophyll loss and lower Malondialdehyde (MDA) production in relation to wild-type plants. Moreover, transgenic seeds exhibited higher germination rates than wild-type seeds under water deficit. Overall, our results highlight the presence of transgenic Rab28 protein in nucleolar structures and point to the potential of group 5 LEA Rab28 gene as candidate to enhance stress tolerance in maize plants.


Assuntos
Regulação da Expressão Gênica de Plantas , Proteínas de Plantas/metabolismo , Zea mays/fisiologia , Nucléolo Celular/metabolismo , Clorofila/metabolismo , Desidratação , Expressão Gênica , Pressão Osmótica , Fenótipo , Folhas de Planta/citologia , Folhas de Planta/genética , Folhas de Planta/fisiologia , Proteínas de Plantas/genética , Raízes de Plantas/citologia , Raízes de Plantas/genética , Raízes de Plantas/fisiologia , Plantas Geneticamente Modificadas , Regiões Promotoras Genéticas , Plântula/citologia , Plântula/genética , Plântula/fisiologia , Sementes/citologia , Sementes/genética , Sementes/fisiologia , Água/metabolismo , Zea mays/citologia , Zea mays/genética
8.
Mol Plant ; 5(4): 817-30, 2012 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-22147756

RESUMO

Cinnamyl alcohol dehydrogenase (CAD) is a key enzyme involved in the last step of monolignol biosynthesis. The effect of CAD down-regulation on lignin production was investigated through a transgenic approach in maize. Transgenic CAD-RNAi plants show a different degree of enzymatic reduction depending on the analyzed tissue and show alterations in cell wall composition. Cell walls of CAD-RNAi stems contain a lignin polymer with a slight reduction in the S-to-G ratio without affecting the total lignin content. In addition, these cell walls accumulate higher levels of cellulose and arabinoxylans. In contrast, cell walls of CAD-RNAi midribs present a reduction in the total lignin content and of cell wall polysaccharides. In vitro degradability assays showed that, although to a different extent, the changes induced by the repression of CAD activity produced midribs and stems more degradable than wild-type plants. CAD-RNAi plants grown in the field presented a wild-type phenotype and produced higher amounts of dry biomass. Cellulosic bioethanol assays revealed that CAD-RNAi biomass produced higher levels of ethanol compared to wild-type, making CAD a good target to improve both the nutritional and energetic values of maize lignocellulosic biomass.


Assuntos
Oxirredutases do Álcool/genética , Biocombustíveis , Celulose/metabolismo , Regulação para Baixo/genética , Etanol/metabolismo , Lignina/biossíntese , Zea mays/genética , Oxirredutases do Álcool/deficiência , Oxirredutases do Álcool/metabolismo , Parede Celular/metabolismo , Flavonoides/química , Flavonoides/metabolismo , Fenóis/química , Fenóis/metabolismo , Caules de Planta/citologia , Caules de Planta/genética , Caules de Planta/crescimento & desenvolvimento , Caules de Planta/metabolismo , Plantas Geneticamente Modificadas , Interferência de RNA , Solubilidade , Zea mays/citologia , Zea mays/crescimento & desenvolvimento , Zea mays/metabolismo
9.
Plant J ; 64(4): 633-44, 2010 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-21070416

RESUMO

Few regulators of phenylpropanoids have been identified in monocots having potential as biofuel crops. Here we demonstrate the role of the maize (Zea mays) R2R3-MYB factor ZmMYB31 in the control of the phenylpropanoid pathway. We determined its in vitro consensus DNA-binding sequence as ACC(T)/(A) ACC, and chromatin immunoprecipitation (ChIP) established that it interacts with two lignin gene promoters in vivo. To explore the potential of ZmMYB31 as a regulator of phenylpropanoids in other plants, its role in the regulation of the phenylpropanoid pathway was further investigated in Arabidopsis thaliana. ZmMYB31 downregulates several genes involved in the synthesis of monolignols and transgenic plants are dwarf and show a significantly reduced lignin content with unaltered polymer composition. We demonstrate that these changes increase cell wall degradability of the transgenic plants. In addition, ZmMYB31 represses the synthesis of sinapoylmalate, resulting in plants that are more sensitive to UV irradiation, and induces several stress-related proteins. Our results suggest that, as an indirect effect of repression of lignin biosynthesis, transgenic plants redirect carbon flux towards the biosynthesis of anthocyanins. Thus, ZmMYB31 can be considered a good candidate for the manipulation of lignin biosynthesis in biotechnological applications.


Assuntos
Parede Celular/metabolismo , Regulação da Expressão Gênica de Plantas , Lignina/metabolismo , Regiões Promotoras Genéticas , Zea mays/metabolismo , Antocianinas/biossíntese , Arabidopsis/genética , Arabidopsis/metabolismo , Sequência de Bases , Sítios de Ligação , Genes de Plantas , Malatos/metabolismo , Dados de Sequência Molecular , Fenilalanina/metabolismo , Fenilpropionatos/metabolismo , Proteínas de Plantas/metabolismo , Plantas Geneticamente Modificadas/metabolismo , Técnica de Seleção de Aptâmeros , Estresse Fisiológico , Zea mays/genética
10.
Plant J ; 63(6): 1017-30, 2010 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-20626661

RESUMO

Mitogen-activated protein kinase (MAPK) cascades have important functions in plant stress responses and development and are key players in reactive oxygen species (ROS) signalling and in innate immunity. In Arabidopsis, the transmission of ROS and pathogen signalling by MAPKs involves the coordinated activation of MPK6 and MPK3; however, the specificity of their negative regulation by phosphatases is not fully known. Here, we present genetic analyses showing that MAPK phosphatase 2 (MKP2) regulates oxidative stress and pathogen defence responses and functionally interacts with MPK3 and MPK6. We show that plants lacking a functional MKP2 gene exhibit delayed wilting symptoms in response to Ralstonia solanacearum and, by contrast, acceleration of disease progression during Botrytis cinerea infection, suggesting that this phosphatase plays differential functions in biotrophic versus necrotrophic pathogen-induced responses. MKP2 function appears to be linked to MPK3 and MPK6 regulation, as indicated by BiFC experiments showing that MKP2 associates with MPK3 and MPK6 in vivo and that in response to fungal elicitors MKP2 exerts differential affinity versus both kinases. We also found that MKP2 interacts with MPK6 in HR-like responses triggered by fungal elicitors, suggesting that MPK3 and MPK6 are subject to differential regulation by MKP2 in this process. We propose that MKP2 is a key regulator of MPK3 and MPK6 networks controlling both abiotic and specific pathogen responses in plants.


Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/enzimologia , Arabidopsis/metabolismo , Quinases de Proteína Quinase Ativadas por Mitógeno/metabolismo , Fosfatases da Proteína Quinase Ativada por Mitógeno/metabolismo , Proteínas Quinases Ativadas por Mitógeno/metabolismo , Plantas Geneticamente Modificadas/enzimologia , Plantas Geneticamente Modificadas/metabolismo , Arabidopsis/genética , Arabidopsis/microbiologia , Proteínas de Arabidopsis/genética , Botrytis/patogenicidade , Imunoprecipitação , Microscopia Confocal , Quinases de Proteína Quinase Ativadas por Mitógeno/genética , Fosfatases da Proteína Quinase Ativada por Mitógeno/genética , Proteínas Quinases Ativadas por Mitógeno/genética , Estresse Oxidativo/genética , Estresse Oxidativo/fisiologia , Plantas Geneticamente Modificadas/genética , Plantas Geneticamente Modificadas/microbiologia , Reação em Cadeia da Polimerase , Ralstonia solanacearum/patogenicidade
11.
Plant Mol Biol ; 70(3): 283-96, 2009 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-19238561

RESUMO

The involvement of the maize ZmMYB42 R2R3-MYB factor in the phenylpropanoid pathway and cell wall structure and composition was investigated by overexpression in Arabidopsis thaliana. ZmMYB42 down-regulates several genes of the lignin pathway and this effect reduces the lignin content in all lignified tissues. In addition, ZmMYB42 plants generate a lignin polymer with a decreased S to G ratio through the enrichment in H and G subunits and depletion in S subunits. This transcription factor also regulates other genes involved in the synthesis of sinapate esters and flavonoids. Furthermore, ZmMYB42 affects the cell wall structure and degradability, and its polysaccharide composition. Together, these results suggest that ZmMYB42 may be part of the regulatory network controlling the phenylpropanoid biosynthetic pathway.


Assuntos
Arabidopsis/citologia , Parede Celular/metabolismo , Lignina/biossíntese , Proteínas de Plantas/metabolismo , Zea mays/genética , Arabidopsis/genética , Ésteres/metabolismo , Flavonoides/biossíntese , Regulação da Expressão Gênica de Plantas , Malatos/metabolismo , Fenilpropionatos/metabolismo , Proteínas de Plantas/genética , Plantas Geneticamente Modificadas/genética , Plantas Geneticamente Modificadas/metabolismo , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo
12.
Plant Mol Biol ; 62(6): 809-23, 2006 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-16941210

RESUMO

The maize (Zea mays L.) caffeic acid O-methyl-transferase (COMT) is a key enzyme in the biosynthesis of lignin. In this work we have characterized the involvement of COMT in the lignification process through the study of the molecular mechanisms involved in its regulation. The examination of the maize COMT gene promoter revealed a putative ACIII box, typically recognized by R2R3-MYB transcription factors. We used the sequence of known R2R3-MYB factors to isolate five maize R2R3-MYB factors (ZmMYB2, ZmMYB8, ZmMYB31, ZmMYB39, and ZmMYB42) and study their possible roles as regulators of the maize COMT gene. The factors ZmMYB8, ZmMY31, and ZmMYB42 belong to the subgroup 4 of the R2R3-MYB family along with other factors associated with lignin biosynthesis repression. In addition, the induction pattern of ZmMYB31 and ZmMYB42 gene expression on wounding is that expected for repressors of the maize COMT gene. Arabidopsis thaliana plants over-expressing ZmMYB31 and ZmMYB42 down-regulate both the A. thaliana and the maize COMT genes. Furthermore, the over-expression of ZmMYB31 and ZmMYB42 also affect the expression of other genes of the lignin pathway and produces a decrease in lignin content of the transgenic plants.


Assuntos
Arabidopsis/enzimologia , Metiltransferases/genética , Proteínas de Plantas/metabolismo , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo , Zea mays/enzimologia , Sequência de Aminoácidos , Arabidopsis/genética , Arabidopsis/metabolismo , Regulação para Baixo/genética , Regulação Enzimológica da Expressão Gênica/genética , Regulação da Expressão Gênica de Plantas/genética , Proteínas de Fluorescência Verde/genética , Proteínas de Fluorescência Verde/metabolismo , Lignina/metabolismo , Metiltransferases/metabolismo , Microscopia de Fluorescência , Dados de Sequência Molecular , Fenótipo , Filogenia , Proteínas de Plantas/genética , Plantas Geneticamente Modificadas , Regiões Promotoras Genéticas/genética , Isoformas de Proteínas/genética , Isoformas de Proteínas/metabolismo , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Homologia de Sequência de Aminoácidos , Estresse Mecânico , Zea mays/genética , Zea mays/metabolismo
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...