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Canastra artisanal Minas cheese samples were collected in Minas Gerais – Brazil. The samples were evaluated in order to observe the presence of antimicrobial peptides during 30 days of ripening. Soluble peptides extracted from the cheeses were fractionated by reverse phase liquid chromatography and their fractions evaluated for inhibitory action of E. coli. Fractions containing antimicrobial activity were analyzed by MALDI-TOF/TOF and then peptides were sequenced and identified using MASCOT Daemon coupled with UniProt database. The identified peptides were then validated by SCAFFOLD application. The peptides present in fractions with antimicrobial activity were RPKHPIKHQ, RPKHPIKHQG, RPKHPIKHQGLPQ and RPKHPIKHQGLPQE, HQPHQPLPPT and MHQPHQPLPPT. Peptide sequences PKHPIKHQ, RPKHPIKHQG, RPKHPIKHQGLPQ and RPKHPIKHQGLPQE were originated from αs1-casein and are their fragments belonging to Isracidine, which in turn is a well known antimicrobial peptide. The HQPHQPLPPT and MHQPHQPLPPT peptides were related to β-casein and were isolated in other studies, but their biological activities are still unknown.

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. Aproteína 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. 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.

Proteomics evaluates biological events by analysis of the expression of proteins in cells or tissues under different physiological situations. For plant proteomics, in order to maintain similar cultivation conditions, treated and non-treated plants are generally cultivated under the same environment without considering changes by the treated plants in protein expression of non-treated neighboring plants. The aim of this work was, by proteomics, assess the differential expression of proteins in non-wounded (non-treated) and wounded (treated) leaves of bell pepper (Capsicum annuum L. ‘Magali R’) by mechanical injury, when plants were grown physically nearby or not. At 40 days of cultivation, some plants were wounded by mechanical injury in all expanded leaves (wounds, F), some plants were maintained as non-injured plants, or being grown near to F plants (NFP, 0.15 m ) or being grown away from F (NFL, 10 m). NFP and NFL plant leaves were harvested at 12, 48, and 168 h after injury of F plants, and the NFL and NFP extracts were analyzed by two-dimensional electrophoresis (2-DE). The protein profiles were compared using Image Master and the proteins were identified using mass spectrometry. NFP 12 h extract presented a lower protein concentration; for 48 h and 168 h, the protein was similar for NFL and NFP. For 2-DE, no significant difference was observed between NFP 12 h and NFL 12 h. However, NFP 48 h showed a higher expression of proteins involved in plant defense. For NFP 168 h, an increased expression of proteins involved in normal metabolism was detected. These results indicated that defense responses were developed by NFP plants considering the proximity of non-wounded plants from wounded plants during cultivation, with volatile compounds involvement. In this sense, it should be emphasized the importance of the choice of the growth conditions for the control-treatments, not only for proteomics.