Some 2S albumin from peanut seeds exhibits inhibitory activity against Aspergillus flavus

The potential of plant proteins as antifungal agents for agricultural applications

Fungal pathogens induce a variety of diseases in both plants and post-harvest food crops, resulting in significant crop losses for the agricultural industry. Although the usage of chemical-based fungicides is the most common way to control these diseases, they damage the environment, have the potential to harm human and animal life, and may lead to resistant fungal strains. Accordingly, there is an urgent need for diverse and effective agricultural fungicides that are environmentally- and eco-friendly. Plants have evolved various mechanisms in their innate immune system to defend against fungal pathogens, including soluble proteins secreted from plants with antifungal activities. These proteins can inhibit fungal growth and infection through a variety of mechanisms while exhibiting diverse functionality in addition to antifungal activity. In this mini review, we summarize and discuss the potential of using plant antifungal proteins for future agricultural applications from the perspective of bioengineering and biotechnology.

Gene expression and spatiotemporal localization of antifungal chitin-binding proteins during Moringa oleifera seed development and germination

Chitin-binding proteins behave as storage and antifungal proteins in the seeds of Moringa oleifera. Moringa oleifera is a tropical multipurpose tree. Its seed constituents possess coagulant, bactericidal, fungicidal, and insecticidal properties. Some of these properties are attributed to a group of polypeptides denominated M. oleifera chitin-binding proteins (in short, Mo-CBPs). Within this group, Mo-CBP₂, Mo-CBP₃, and Mo-CBP₄ were previously purified to homogeneity. They showed high amino acid similarity with the 2S albumin storage proteins. These proteins also presented antimicrobial activity against human pathogenic yeast and phytopathogenic fungi. In the present study, the localization and expression of genes that encode Mo-CBPs and the biosynthesis and degradation of the corresponding proteins during morphogenesis and maturation of M. oleifera seeds at 15, 30, 60, and 90 days after anthesis (DAA) and germination, respectively, were assessed. The Mo-CBP transcripts and corresponding proteins were not detected at 15 and 30 days after anthesis (DAA). However, they accumulated at the latter stages of seed maturation (60 and 90 DAA), reaching the maximum level at 60 DAA. The degradation kinetics of Mo-CBPs during seed germination by in situ immunolocalization revealed a reduction in the protein content 48 h after sowing (HAS). Moreover, Mo-CBPs isolated from seeds at 60 and 90 DAA prevented the spore germination of Fusarium spp. Taken together, these results suggest that Mo-CBPs play a dual role as storage and defense proteins in the seeds of M. oleifera.

Evaluation of some effects on plant metabolism through proteins and enzymes in transgenic and non-transgenic soybeans after cultivation with silver nanoparticles

To evaluate the effects of silver nanoparticles (AgNP) exposition, transgenic (through gene cp4EPSPS) and non-isogenic non-transgenic soybeans were cultivated in the presence or absence of AgNP or silver nitrate (AgNO3) at 50 mg/kg of silver. Physiological aspects of the plants including mass production and development of roots, proteomics such as protein amount and differential proteins, enzymes and lipid peroxidation were determined after exposition. The mass production of non-transgenic plants treated with AgNP or AgNO3 was decreased by 25 and 19%, respectively, on their mass based, while for transgenic soybean this effect was observed for AgNP cultivation only. Fifty-nine proteins were identified from the differentially abundant spots by two-dimensional difference gel electrophoresis and nano-electrospray ionization liquid chromatography coupled tandem mass spectrometry. Identified species as ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO), ATP synthase, superoxide dismutase (SOD), related to plant metabolism were less abundant for the cultivation with either AgNP and AgNO3 than the control. Finally, this work demonstrated significant correlation as evidenced by changes in lipid peroxidation content and catalase activity, which were a result of exposure to either AgNP or AgNO3 cultivations. Further, necrotic areas in the basal part of the stems and damage or chlorotic areas were found in the leaves. SIGNIFICANCE: Once nanoparticles have been employed for several applications in recent years and they can be released in the environmental matrices, this study highlights proteomic and enzymatic alterations in transgenic and non-transgenic soybeans, an important crop, after cultivation with silver nanoparticles. Such strategy employing proteomic and enzymatic approaches to evaluate soybeans exposed to silver nanoparticles has not yet been reported. Therefore, the results obtained in this study can expand the information concerning the effects of silver nanoparticles in soybean plants.

A 2S Albumin from the Seed Cake of Ricinus communis Inhibits Trypsin and Has Strong Antibacterial Activity against Human Pathogenic Bacteria

Hospital-acquired infections caused by antibiotic-resistant bacteria threaten the lives of many citizens all over the world. Discovery of new agents to hinder bacterial development would have a significant impact on the treatment of infections. Here, the purification and characterization of Rc-2S-Alb, a protein that belongs to the 2S albumin family, from Ricinus communis seed cake, are reported. Rc-2S-Alb was purified after protein extraction with Tris-HCl buffer, pH 7.5, fractionation by ammonium sulfate (50-75%), and chromatography on Phenyl-Sepharose and DEAE-Sepharose. Rc-2S-Alb, a 75 kDa peptide, displays trypsin inhibitory activity and has high in vitro antibacterial activity against Bacillus subtilis, Klebsiella pneumonia, and Pseudomonas aeruginosa, which are important human pathogenic bacteria. Atomic force microscopy studies indicated that Rc-2S-Alb disrupts the bacterial membrane with loss of the cytoplasm content and ultimately bacterial death. Therefore, Rc-2S-Alb is a powerful candidate for the development of an alternative drug that may help reduce hospital-acquired infections.

New insights into the structure and mode of action of Mo-CBP3, an antifungal chitin-binding protein of Moringa oleifera seeds

Mo-CBP3 is a chitin-binding protein purified from Moringa oleifera Lam. seeds that displays inhibitory activity against phytopathogenic fungi. This study investigated the structural properties and the antifungal mode of action of this protein. To this end, circular dichroism spectroscopy, antifungal assays, measurements of the production of reactive oxygen species and microscopic analyses were utilized. Mo-CBP3 is composed of 30.3% α-helices, 16.3% β-sheets, 22.3% turns and 30.4% unordered forms. The Mo-CBP3 structure is highly stable and retains its antifungal activity regardless of temperature and pH. Fusarium solani was used as a model organism for studying the mechanisms by which this protein acts as an antifungal agent. Mo-CBP3 significantly inhibited spore germination and mycelial growth at 0.05 mg.mL-1. Mo-CBP3 has both fungistatic and fungicidal effects, depending on the concentration used. Binding of Mo-CBP3 to the fungal cell surface is achieved, at least in part, via electrostatic interactions, as salt was able to reduce its inhibitory effect. Mo-CBP3 induced the production of ROS and caused disorganization of both the cytoplasm and the plasma membrane in F. solani cells. Based on its high stability and specific toxicity, with broad-spectrum efficacy against important phytopathogenic fungi at low inhibitory concentrations but not to human cells, Mo-CBP3 has great potential for the development of new antifungal drugs or transgenic crops with enhanced resistance to phytopathogens.

The use of versatile plant antimicrobial peptides in agribusiness and human health

Plant immune responses involve a wide diversity of physiological reactions that are induced by the recognition of pathogens, such as hypersensitive responses, cell wall modifications, and the synthesis of antimicrobial molecules including antimicrobial peptides (AMPs). These proteinaceous molecules have been widely studied, presenting peculiar characteristics such as conserved domains and a conserved disulfide bond pattern. Currently, many AMP classes with diverse modes of action are known, having been isolated from a large number of organisms. Plant AMPs comprise an interesting source of studies nowadays, and among these there are reports of different classes, including defensins, albumins, cyclotides, snakins and several others. These peptides have been widely used in works that pursue human disease control, including nosocomial infections, as well as for agricultural purposes. In this context, this review will focus on the relevance of the structural-function relations of AMPs derived from plants and their proper use in applications for human health and agribusiness.