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2.
J Plant Physiol ; 169(10): 965-70, 2012 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-22575056

RESUMO

Ultrastructural and molecular studies have provided experimental evidence for the classification of cucurbits as symplastic loaders, mainly translocating the raffinose family oligosaccharides (RFOs) raffinose and stachyose. Earlier studies established that cucumber mosaic virus (CMV) infection causes a significant increase in the sucrose-to-RFO ratio in the phloem sap of melon plants. The alteration in phloem sap sugar composition was associated with upregulation of CmSUT1 transcript within the vascular bundles. The current research aimed to explore the effect of CMV infection on the enzymes involved in symplastic phloem loading and RFO biosynthesis. Viral infection did not affect the activity of either raffinose or stachyose synthases in source leaves, but caused upregulation of the respective transcripts. Interestingly, activity of galactinol synthase was higher in CMV-infected leaves, associated with upregulation of CmGAS2. A significant increase in CmGAS2 expression in source leaves of melon plants exposed to high temperatures indicated that this response is common for both biotic and abiotic stresses. However, the effect of CMV or heat stress on phloem sap sugar composition is not due to alteration in RFO biosynthesis.


Assuntos
Vias Biossintéticas , Cucumovirus/fisiologia , Cucurbitaceae/enzimologia , Cucurbitaceae/virologia , Temperatura Alta , Doenças das Plantas/virologia , Rafinose/biossíntese , Vias Biossintéticas/genética , Cromatografia Líquida , Cucurbitaceae/genética , Galactosiltransferases/genética , Galactosiltransferases/metabolismo , Regulação da Expressão Gênica de Plantas , Espectrometria de Massas , Oligossacarídeos/metabolismo , Doenças das Plantas/genética , Folhas de Planta/enzimologia , Folhas de Planta/genética , Reação em Cadeia da Polimerase em Tempo Real , Estresse Fisiológico/genética , Sacarose/metabolismo , Regulação para Cima/genética
3.
Plant J ; 66(2): 366-74, 2011 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-21241389

RESUMO

Based on the high density of plasmodesmata interconnecting the intermediary cells and their neighboring phloem parenchyma or bundle-sheath cells, and based on the insensitivity to the sucrose transport inhibitor p-chloromercuribenzenesulfonic acid (PCMBS), cucurbits have been concluded to be symplastic loaders. In the present study, we identified and characterized the full-length sequence of sucrose transporter gene (CmSUT1) from melon (Cucumis melo L. cv. Hale's best jumbo). In vitro experiments confirmed that the identified gene product has sucrose transporter activity in baker's yeast. Healthy and cucumber mosaic virus (CMV)-infected melon plants were employed to examine sucrose transporter activity in planta. Pretreatment with PCMBS inhibited loading of newly fixed ¹4CO2 into minor veins of CMV-infected plants. Moreover, CMV infection caused significant increase in CmSUT1 transcripts expression, mainly in vascular bundles of minor veins, which was associated with elevated sucrose content in phloem sap collected from source-leaf petioles. We propose that cucurbit plants contain the machinery for apoplastic phloem loading and that CMV infection causes a quantitative shift in the mode by which photoassimilates are loaded into the sieve tube.


Assuntos
Cucumis melo/genética , Proteínas de Membrana Transportadoras/metabolismo , Folhas de Planta/genética , Proteínas de Plantas/metabolismo , Sacarose/metabolismo , Cucumis melo/metabolismo , Cucumis melo/virologia , Cucumovirus/patogenicidade , Floema/metabolismo , Filogenia , Folhas de Planta/metabolismo , Folhas de Planta/virologia
4.
Eur J Immunol ; 37(6): 1584-93, 2007 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-17458859

RESUMO

Erythropoietin (Epo) is the main erythropoietic hormone. Recombinant human Epo (rHuEpo) is thus used in clinical practice for the treatment of anemia. Accumulating data reveals that Epo exerts pleiotropic activities. We have previously shown an anti-neoplastic activity of Epo in murine multiple myeloma (MM) models, and in MM patients. Our findings that this anti-neoplastic effect operates via CD8+ T lymphocytes led us to hypothesize that Epo possesses a wider range of immunomodulatory functions. Here we demonstrate the effect of Epo on B lymphocyte responses, focusing on three experimental models: (i) tumor-bearing mice, (5T2 MM mouse); (ii) antigen-injected healthy mice; and (iii) antigen-injected transgenic mice (tg6), overexpressing human Epo. In the MM model, despite bone marrow dysfunction, Epo-treated mice retained higher levels of endogenous polyclonal immunoglobulins, compared to their untreated controls. In both Epo-treated wild type and tg6 mice, Epo effect was manifested in the higher levels of splenocyte proliferative response induced in vitro by lipopolysaccharide. Furthermore, these mice had increased in vivo production of anti-dinitrophenyl (DNP) antibodies following immunization with DNP-keyhole limpet hemocyanin. Epo-treated mice showed an enhanced immune response also to the clinically relevant hepatitis B surface antigen. These findings suggest a potential novel use of rHuEpo as an immunomodulator.


Assuntos
Adjuvantes Imunológicos/farmacologia , Formação de Anticorpos/efeitos dos fármacos , Eritropoetina/farmacologia , Adjuvantes Imunológicos/genética , Animais , Anticorpos Monoclonais/imunologia , Anticorpos Monoclonais/farmacologia , Formação de Anticorpos/imunologia , Linfócitos B/citologia , Linfócitos B/efeitos dos fármacos , Linfócitos B/imunologia , Complexo CD3/imunologia , Proliferação de Células/efeitos dos fármacos , Eritropoetina/genética , Eritropoetina/uso terapêutico , Feminino , Hemocianinas/imunologia , Antígenos de Superfície da Hepatite B/imunologia , Humanos , Imunoglobulina G/sangue , Cadeias gama de Imunoglobulina/sangue , Cadeias kappa de Imunoglobulina/sangue , Lipopolissacarídeos/farmacologia , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Mieloma Múltiplo/sangue , Mieloma Múltiplo/tratamento farmacológico , Proteínas Recombinantes/farmacologia , Proteínas Recombinantes/uso terapêutico , Análise de Sobrevida , Linfócitos T/citologia , Linfócitos T/efeitos dos fármacos , Linfócitos T/imunologia , Vacinação
5.
EMBO J ; 26(7): 1749-60, 2007 Apr 04.
Artigo em Inglês | MEDLINE | ID: mdl-17347651

RESUMO

Autophagy is a major catabolic pathway by which eukaryotic cells degrade and recycle macromolecules and organelles. This pathway is activated under environmental stress conditions, during development and in various pathological situations. In this study, we describe the role of reactive oxygen species (ROS) as signaling molecules in starvation-induced autophagy. We show that starvation stimulates formation of ROS, specifically H(2)O(2). These oxidative conditions are essential for autophagy, as treatment with antioxidative agents abolished the formation of autophagosomes and the consequent degradation of proteins. Furthermore, we identify the cysteine protease HsAtg4 as a direct target for oxidation by H(2)O(2), and specify a cysteine residue located near the HsAtg4 catalytic site as a critical for this regulation. Expression of this regulatory mutant prevented the formation of autophagosomes in cells, thus providing a molecular mechanism for redox regulation of the autophagic process.


Assuntos
Autofagia , Cisteína Endopeptidases/metabolismo , Espécies Reativas de Oxigênio/metabolismo , Sequência de Aminoácidos , Animais , Proteínas Relacionadas à Autofagia , Células CHO , Cricetinae , Cricetulus , Cisteína/metabolismo , Cisteína Endopeptidases/química , Ativação Enzimática , Privação de Alimentos , Células HeLa , Humanos , Camundongos , Modelos Biológicos , Dados de Sequência Molecular , Mutação/genética , Oxirredução , Fosfatidilinositol 3-Quinases/metabolismo , Filogenia
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