Extracellular Proteome of Bacillus amyloliquefaciens KPS46 and Its Effect on Enhanced Growth Promotion and Induced Resistance Against Bacterial Pustule on Soybean Plant

Abstract

Bacillus amyloliquefaciens strain KPS46 is gram positive that has been found to be effective in controlling various diseases and improving crop yield under greenhouse and field conditions. This study was investigated for KPS46 ability to activate extracellular protein elicitors in enhanced plant growth and induced systemic resistance of soybean plants. Soybean cv. Spencer seeds treated with KPS46 increased root and shoot length, biomass by more than 20-40% and the reduced bacterial pustule disease severity up to 50% when compared with the non-treated control. Bioassay data showed that seedling growth phenotype increased by KPS46 was significant upregulation of 20- elicited extracellular protein spots, whereas sterile distilled water had no effect on either enhanced plant growth or induced resistance. To investigate the proteins involved in growth promotion and induced resistance mechanisms, two-dimensional gel electrophoresis was used to separate extracellular proteins secreted by KPS46 wild type and by N19G1, a UV-derived mutant of KPS46 with reduced production of extracellular proteins and lacking growth promotion and induced resistance activity. Using the 2D-PAGE, the extracellular protein of B. amyloliquefaciens KPS46 grown in nutrient glucose broth was studied. The identity and putative function of twenty proteins secreted by KPS46 but not by N19G1 were determined. The 20 extracellular protein spots were identified that were known to be secreted by various mechanisms. These extracellular proteomes of the strain KPS46 included proteins from different functional classes and some proteins of yet unknown function. To our knowledge, this was the first two-dimensional extracellular proteome map of a PGPRs, KPS46. The analysis revealed a number of proteins which might be involved in plant growth promotion and induced resistance by acting as plant growth regulators, accumulating bio-fertilizer/ nutrients, producing antibiotic compounds, stimulating metabolism or functioning in defense against stress factors.