Bioprospection of natural compounds to be used as plant protection offers exciting possibilities in agribusiness. ÔSamaraÕ (SM) and ÔSunshineÕ (SH) cultivars of bell pepper are resistant against some plant pathogens, and leaf antimicrobial peptides could account for their defence system. In the present study, 5-7 kDa peptides were partially purified from cell wall extract (CWE) of bell pepper leaves and further resolved by ionexchange chromatography. The cationic and anionic peptide-enriched fractions from both SM-CWE and SH-CWE strongly inhibited in vitro growth of Ralstonia solanacearum and Clavibacter michiganensis ssp. michiganensis. Peptide extraction and purificationSoluble extract (SE) and cell wall extract (CWE) were obtained from bell pepper leaves of SM or SH cultivars (Segura et al., 1998). Frozen leaves (3 g) were powdered and extracted with 12 ml of 100 mm Tris-HCl www.blackwell-synergy.com

Resumo -O objetivo deste trabalho foi avaliar, por meio de enzimas marcadoras, a indução de resistência à ferrugem-asiática-da-soja em genótipos de soja contrastantes quanto à suscetibilidade a Phakopsora pachyrhizi. A proteína total e as atividades de cinco enzimas marcadoras da indução de resistência (lipoxigenases, peroxidases, fenilalanina amônia-liase, quitinases e β-1,3-glucanases) foram avaliadas em extratos de folhas de plantas de soja dos genótipos Embrapa 48 (suscetível) e PI 561356 (resistente), submetidas à inoculação ou não com o patógeno. Foram observadas respostas de defesa discrepantes entre os dois genótipos e entre os tempos de coleta (12, 72 e 168 horas após inoculação). A resposta de indução dessas enzimas assemelha-se à defesa bifásica, para Embrapa 48, e é consistente com o observado para outros patossistemas. No entanto, o genótipo PI 561356 respondeu com diminuição da concentração de proteína total e das atividades enzimáticas, o que indica redução do metabolismo geral das plantas infectadas. Há um importante mecanismo de resistência do genótipo PI 561356, ainda não relatado, embasado em vias que envolvem essas enzimas marcadoras e em mecanismos que utilizam menor concentração de proteínas, como os de via metabólica de resposta em cascata.Termos para indexação: Glycine max, Phakopsora pachyrhizi, atividade enzimática, mecanismos de defesa, resistência sistêmica, resposta em cascata. Differentially regulated induced resistance marker enzymes in soybean genotypes resistant and susceptible to Asian soybean rustAbstract -The objective of this work was to evaluate induced resistance to Asian soybean rust by means of enzyme activities in soybean genotypes contrasting as to their susceptibility to Phakopsora pachyrhizi. Total protein and the activities of five induced resistance marker enzymes (lipoxygenases, peroxidases, phenylalanine ammonia-lyase, chitinases and β-1,3-glucanases) were evaluated in leaf extracts of soybean plants of the genotypes Embrapa 48 (susceptible) and PI 561356 (resistant), inoculated or not with the pathogen. Discrepant defense responses were obtained between the two genotypes and among the leaf harvest times (12, 72, and 168 hours after inoculation). The induction response of these enzymes resembles the biphasic defense in Embrapa 48 and is consistent with that observed in other pathological systems. However, the genotype PI 561356 responded with a decrease in total protein concentration and in enzymatic activities, indicating a general reduction in the metabolism of the infected plants. There is an important mechanism of resistance for the genotype PI 561356, not yet reported, which is grounded on the metabolic ways involving these induced resistance marker enzymes and on the mechanisms that use lower concentrations of total protein, such as the ones with metabolic pathways in response cascade.

Some varieties of eggplant are little susceptible to some plant pathogens, and antimicrobial peptides (AMPs) could be part of this innate-defence mechanism. This work aimed to evaluate the in vitro antimicrobial activity of peptide-enriched fractions from cell wall extracts (CWE) and soluble extracts (SE) from young plants and fully expanded leaves of eggplants against Ralstonia solanacearum and Clavibacter michiganensis ssp. michiganensis growth. The results indicated that the highest inhibition level of the multiplication of both bacteria was obtained with CWE from 5-cm-height plants, while SE promoted the highest inhibition rate when 15-cm-height plants or fully expanded leaves were analysed. These results suggest that young plants exhibit an innate-defence mechanism, very likely involving cell wall AMPs action to minimize plant antimicrobial invasion, while expanded leaves could produce soluble defence molecules. The inhibition rate was dependent for the extract concentration and the extracts were more effective against the growth of Gram-negative bacteria.

Compostos naturais, incluindo-se peptídios antimicrobianos, vêm se destacando como fontes de agentes de defesa contra fitopatógenos de importância comercial. Esse trabalho visou obter frações peptídicas a partir de extratos de folhas de berinjela e a v a l i a r a s a t i v i d a d e s a n t i m i c r o b i a n a s c o n t r a d u a s b a c t é r i a s fitopatogênicas. Os pools peptídicos catiônicos, PC1 e PC2 e o aniônico PA obtidos de extratos solúvel (ES) e de parede celular

RESUMO:Extratos aquosos da planta medicinal Achillea millefolium contêm macromoléculas de interesse para desenvolver fitodefensivos para a agricultura. Duas frações de mil folhas foram obtidas por ultrafiltração, E1 (contendo moléculas maiores que 30 kDa), e E3 (peptídeos entre 1 e 10 kDa) que inibiram o crescimento das bactérias fitopatogênicas Ralstonia solanacearum, gramnegativa, e Clavibacter michiganensis subsp. michiganensis, gram-positiva, com dependência de concentração. Os valores de concentração inibitória mínima (CIM) para ambos os extratos e bactérias foram baixos, entre 20 e 80mM. A CIM relativa à proteína total evidenciou a presença de macromoléculas muito ativas em E3, embora com baixa concentração proteica. E3 se aplica à prospecção de peptídeos antimicrobianos. Estimar a CIM relativa à quantidade de amostra vegetal valorizou o potencial antimicrobiano natural de E1, que contém alta concentração proteica. E1e E3 se aplicam ao desenvolvimento de fitodefensivos para uso biotecnológico. A ultrafiltração fracionou as amostras de forma nativa, rápida, e com baixo custo; além de dessalinizar, clarificar, purificar, e concentrar E1 e E3. Esse estudo inédito sobre a separômica e a ação antimicrobiana de extratos macromoleculares aquosos de mil folhas sugere que plantas cicatrizantes podem apresentar grande potencial para desenvolver fitodefensivos agrícolas naturais não danosos, à semelhança de medicamentos fitoterápicos.Palavras-chave: Macromoléculas de defesa, peptídeos antimicrobianos, Ralstonia solanacearum, Clavibacter michiganensis subsp. michiganensis, concentração inibitória mínima relativa.ABSTRACT: Agrochemicals in medicinal plants: hydrophilic macromolecules from leaves of "mil folhas" (Achillea millefolium L.) inhibit in vitro growth of phytopathogenic bacteria. Aqueous extracts from the medicinal plant Achillea millefolium contain macromolecules of interest to develop agrochemicals for agriculture. Two fractions of "mil folhas" were obtained by ultrafiltration, E1 (containing molecules larger than 30 kDa) and E3 (peptides between 1 and 10 kDa), which inhibited the growth of phytopathogenic bacteria Ralstonia solanacearum, gramnegative, and Clavibacter michiganensis subsp. michiganensis, gram-positive, concentrationdependent. The values of minimum inhibitory concentration (MIC) for both extracts and both bacteria were low, ranging from 20 to 80mM. The MIC relative to total protein evidenced the presence of very active macromolecules in E3, although showing low protein concentration. E3 applies to the prospection of antimicrobial peptides. The estimated MIC relative to the amount of plant sample valued the natural antimicrobial potential of E1, which contains high protein concentration. E1 and E3 can be used in the development of agrochemicals for biotechnological purposes. The ultrafiltration procedure fractionated the samples in a rapid and native way and at a low cost; it also desalted, clarified, concentrated and purified both E1 and E3. This pioneering study on the separomics and on the a...