RESUMO
The role of active oxygen species has been studied in spreading soft-rot lesions caused by the necrotrophic fungal pathogen Botrytis cinerea Pers.:Fr. in leaves of four genotypes of French bean (Phaseolus vulgaris L.). Large increases were observed for the aldehydic end-products of oxidative damage, malondialdehyde and 4-hydroxy-2-nonenal, as a result of infection in each of the genotypes studied. Similar increases were found in a stable free radical and g=4.27 Fe(III) signals, but not Mn(II) signals, in electron paramagnetic resonance spectra. These changes were accompanied by large decreases in ascorbic acid levels, with changes in the antioxidant glutathione being genotype dependent.
Assuntos
Fabaceae/metabolismo , Estresse Oxidativo/fisiologia , Doenças das Plantas , Plantas Medicinais , Aldeídos/metabolismo , Ácido Ascórbico/metabolismo , Biomarcadores/análise , Botrytis , Espectroscopia de Ressonância de Spin Eletrônica , Radicais Livres/metabolismo , Genótipo , Glutationa/metabolismo , Técnicas In Vitro , Peroxidação de Lipídeos/fisiologia , Malondialdeído/metabolismo , Folhas de Planta/metabolismoRESUMO
A potato gene encoding a putative WRKY protein was isolated from a cDNA library enriched by suppression subtractive hybridization for sequences upregulated 1 h postinoculation with Erwinia carotovora subsp. atroseptica. The cDNA encodes a putative polypeptide of 172 amino acids, containing a single WRKY domain with a zinc finger motif and preceded by a potential nuclear localization site. St-WRKY1 was strongly upregulated in compatible, but only weakly in incompatible, interactions with Phytophthora infestans where, in all cases, it was coregulated with class I endochitinase, associating its expression with a known defense response. Whereas St-WRKY1 was strongly induced by E. carotovora culture filtrate (CF), confirming it to be an elicitor-induced gene, no such induction was detected after treatment with salicylic acid, methyl jasmonate, ethylene, or wounding. St-WRKY1 was upregulated by treatment of potato leaves with CFs from recombinant Escherichia coli containing plasmids expressing E. carotovora pectate lyase genes pelB and pelD, suggesting that either proteins encoded by these genes, or oligogalacturonides generated by their activity, elicit a potato defense pathway associated with St-WRKY1.
Assuntos
Quitinases/genética , Proteínas de Ligação a DNA/genética , Pectobacterium carotovorum/fisiologia , Phytophthora/fisiologia , Proteínas de Plantas , Solanum tuberosum/genética , Solanum tuberosum/microbiologia , Fatores de Transcrição/genética , Motivos de Aminoácidos , Sequência de Aminoácidos , Parede Celular/metabolismo , Quitinases/biossíntese , Proteínas de Ligação a DNA/biossíntese , Proteínas de Ligação a DNA/química , Escherichia coli/genética , Escherichia coli/fisiologia , Regulação da Expressão Gênica de Plantas , Biblioteca Gênica , Dados de Sequência Molecular , Sinais de Localização Nuclear , Polissacarídeo-Liases/genética , Polissacarídeo-Liases/metabolismo , Estrutura Terciária de Proteína , Proteínas Recombinantes/metabolismo , Alinhamento de Sequência , Transdução de Sinais , Solanum tuberosum/enzimologia , Fatores de Transcrição/biossíntese , Fatores de Transcrição/química , Regulação para Cima , Dedos de ZincoRESUMO
A potato cysteine protease (cyp) cDNA expressed at an early stage of an incompatible interaction with Phytophthora infestans was isolated. Both the nucleotide and deduced amino acid sequences are highly homologous to those of a tomato cysteine protease, CYP1. Striking protein similarity to all known cathepsins in animals, particularly cathepsin K, was also observed. However, unlike cathepsins, a granulin binding domain is located near the carboxyl terminus of the putative CYP protein. In animals, granulins bind to receptors in the plasma membrane and signal cell growth and division. A ribonuclease protection assay demonstrated that the cyp gene is tightly regulated and is induced 15 h post inoculation with P. infestans in potato leaves either with high field resistance or in which a resistance (R) gene is activated. We conclude that a common signaling pathway is activated in each form of resistance.
Assuntos
Cisteína Endopeptidases/genética , Regulação Enzimológica da Expressão Gênica , Regulação da Expressão Gênica de Plantas , Phytophthora/patogenicidade , Solanum tuberosum/microbiologia , Sequência de Aminoácidos , Sequência de Bases , DNA Complementar , Dados de Sequência Molecular , Homologia de Sequência de Aminoácidos , Solanum tuberosum/enzimologiaRESUMO
Antimicrobial substances were produced by Bacillus subtilis BS 107 in a defined medium and isolated from culture filtrate by precipitation at pH 2.5. Active fractions were extracted in ethyl acetate, acetone, and 80% ethanol and purified by thin-layer chromatography (TLC) on silica gel plates developed with an ethanol-water mixture (2:1, v/v). In each case, a band with a Rf of 0.75 formed an inhibitory zone when the TLC plates were placed in contact with agar seeded with test cultures of the Erwinia spp. The antibiotic was released into the culture medium during early stages of growth of Bacillus subtilis BS 107 but higher amounts were released in older cultures. The antibiotic was resistant to the action of nucleases, proteases, and lipase. It was stable when autoclaved twice for 35 min at 2 atm (1 atm = 101.325 kPa) in acidic, neutral, and alkaline solutions. It remained active over the pH range of 1-14 during 1 month of observation and exhibited no loss of antimicrobial activity when stored at 4 degrees C for over 1 year. Bacillus subtilis BS 107 showed activity in vitro and in vivo against Erwinia carotovora subsp. atroseptica and Erwinia carotovora subsp. carotovora, the causal agents of potato blackleg and tuber soft rot. The application of an antagonist or its antibiotic to cut potato tissues prevented or reduced symptoms of the diseases. The antibiotic was active in vitro against a broad spectrum of bacterial and fungal species.