ABSTRACT Plant growth-promoting bacteria (PGPB) comprise part of plant microbiome of biotechnological interest due to their potential to decrease the use of agrochemicals in agriculture. Among the commonly found PGPB species, the Pseudomonas genus is known for high competitiveness and efficiency in expressing growth-promotion traits. To increase the contribution of diazotrophic Pseudomonas sp. to the plant nitrogen nutrition, the strain AZM-01 was chemically mutagenized with methyl methanesulfonate (MMS), following the selection for resistance to ethylenediamine (EDA). From the 13 EDA-resistant mutant strains selected, four showed increased the ammonium excretion, with the highest value reaching up to 284% increase as compared to the wild strain, and six strains were found to produce significantly more auxins than the wild strain. Two independent inoculation trials with the wild and EDA-resistant Pseudomonas were performed on maize, with the objective to study the influence of bacteria on seed germination and its potential to promote maize growth under N-limiting condition. In general, Pseudomonas inoculation modified the root architecture of germinating seeds, and increased biomass of maize plants grown under N-limiting conditions. Shoot dry weight of maize was increased by inoculation with several EDA-resistant mutants as compared to the strain AZM-01, with emphasis on the EDA-5 strain which supports biomass accumulation at equivalent amount of plants grown under full N supply. Significant correlations between in vitro and in vivo parameters were found although low coefficient values predominate. The strategy of random mutagenesis was found suitable to develop PGPB strains with higher potential to supply maize plants with nitrogen.

Sample preparation is a critical step in two-dimensional gel electrophoresis (2-DE) of plant tissues. Here we describe a phenol/SDS procedure that, although greatly simplified, produced well-resolved and reproducible 2-DE profiles of protein extracts from soybean [Glycine max (L.) Merril] roots. Extractions were made in three replicates using both the original and simplified procedure. To evaluate the quality of the extracted proteins, ten spots were randomly selected and identified by mass spectrometry (MS). The 2-DE gels were equally well resolved, with no streaks or smears, and no significant differences were observed in protein yield, reproducibility, resolution or number of spots. Mass spectra of the ten selected spots were compared with database entries and allowed high-quality identification of proteins. The simplified protocol described here presents considerable savings of time and reagents without compromising the quality of 2-DE protein profiles and compatibility with MS analysis, and may facilitate the progress of proteomics studies of legume-rhizobia interactions.

Abstract The synthesis and structural determination of cinnamates esters derivative let us to obtain some similar products to natural esters isolated from Lafoensia glyptocarpa Koehne, and to evaluate their allelopathic potencial by bioassays of lettuce and tomato seed germination. The substances which promoted more inhibition to seed germination were 3,4-metilenedioxiphenyl hexadecyl acrylate; 3,4-metilenedioxiphenyl hexadecyl propionate; 3,4-metilenedioxi-6-nitrophenyl hexadecyl propionate, and sitosteryl ferulate. The structures were determined by infrared, mass and 1H and 13C NMR spectroscopy.

Resumo A síntese e determinação estrutural de ésteres derivados do ácido cinâmico permitiu obter análogos dos ésteres naturais isolados de Lafoensia glyptocarpa Koehne e avaliar o potencial alelopático dos mesmos através de bioensaios de germinação de sementes de alface e tomate. As substâncias que promoveram maior inibição da germinação das sementes analisadas foram: 3,4-metilenodioxifenil acrilato de hexadecila; 3,4-metilenodioxifenil propionato de hexadecila; 3,4-metilenodioxi-6-nitrofenil propionato de hexadecila; e ferrulato de sitosterila. As estruturas foram determinadas através da análise de dados fornecidos por espectrometria de infravermelho, de massas e de RMN de 1H e 13C.