Cysteine-rich peptides play an important role in the plant defense system. The objective of this study was in silico searching for the genes encoding antimicrobial and signaling peptides in the genome of the tall wheatgrass Thinopyrum elongatum (Host) D.R. Dewey (2n = 14, EE), a wild cereal that is highly resistant to pathogens and abiotic stress. Bioinformatic analysis provided information for the identification in the tall wheatgrass genome of 154 novel genes coding for antimicrobial and signaling peptide precursors belonging to nine families. A number of cysteine-rich peptide genes were found to contain introns. The structure of peptide precursors and the location of the peptide genes on the wheatgrass chromosomes were determined. The highest similarity of the wheatgrass peptide sequences with homologous peptides from plants of the genera Triticum and Aegilops was demonstrated, supporting the cytogenetic data on the relatedness between genome E and genome D, as well as the genomes close to it. The data obtained contribute to the characterization of the molecular components of the Th. elongatum immune system and will serve as the basis for further studies of the mechanisms of resistance, as well as for the scientifically based practical use of this species as the resistance donor in wheat breeding.

Antimicrobial peptides (AMPs) are major components of innate immunity in plants and animals. AMP genes have significant intra- and interspecific polymorphism, the role of which is poorly understood. Previously, by high-throughput transcriptome sequencing of wheat plants, we identified defensin genes up-regulated upon infection with the pathogenic fungus Fusarium oxysporum and/or treatment with resistance inducers. In the present work, a bioinformatic search in NCBI databases for peptide homologs of these defensins was carried out using the sequences of their γ-cores, the sites of the molecules responsible for antimicrobial activity. DEFL1-16 homologs were identified in 95 species of angiosperms belonging to 48 families and 30 orders of monocotyledonous and dicotyledonous plants. The ubiquitous distribution of this defensin in angiosperms suggests its involvement not only in defense but also in other processes in flowering plants. Homologs of other defensins induced by infection were found only in plants of the Poaceae family, which suggests the existence of a Poaceae-specific defense mechanism associated with the expression of these defensins. Among the γ-core variants of wild plant defensins identified in the study, the peptides with better antimicrobial activity compared to wheat may be present, which are of considerable interest for the development of new antibiotics for medicine and agriculture.

Plant cysteine-rich peptides (CRP) play a key role in protection of plants from pathogens and abiotic stress, in symbiosis with bacteria, and in plant development and reproduction. The composition and role of CRPs in tomato Solanum lycopersicum , one of the most important vegetable, has not been studied so far. In this paper, using two approaches, hidden Markov models and regular expressions, in silico identification of tomato CRP families was performed. A bioinformatic analysis of NCBI databases revealed 191 CRP precursors. The peptides found belong to the families of antimicrobial and signaling peptides. Among the antimicrobial peptides, defensins and defensin-like peptides, nonspecific lipid-transfer proteins, thionins, snakins, and hevein- and knottin-like peptides were found. Among signaling peptides, the peptides belonging to the RALF, Ole e 1, Ole e 6, and MEG families were discovered. In addition, peptides with new cysteine motifs were identified. All discovered CRPs are synthesized as pre- or preproproteins. The predicted mature peptides were characterized by cysteine motifs, antimicrobial activity, and domain structure. Thus, for the first time, using bioinformatic approaches, systemic data on the arsenal of CRPs in the tomato genome were obtained, which creates a basis for further functional studies of these peptides and their subsequent use in agriculture to develop new strategies for increasing tomato pathogen resistance, as well as in medicine to create next-generation drugs.

Plants serve as a source of biologically active compounds, the most important of which are antimicrobial peptides (AMPs). AMPs represent an integral part of the defense arsenal of all living beings. Members of the thionin family found only in plants are effective inhibitors of plant pathogens, including bacteria and fungi, which opens up prospects for their practical application as biopesticides to protect plants from diseases. However, the effect of thionins on animal and human pathogens has not been sufficiently studied. Yeast-like fungi of the genus Candida are opportunistic pathogenic microorganisms that occur in 70 % of people without causing disease (M. Dadar et al., 2018). However, in immune-compromised individuals, they can cause a number of serious diseases, the frequency of which has increased significantly in the last two decades. Antimycotics traditionally used to treat Candida infections are not always effective and safe for humans. In this regard, the world is constantly searching for new natural antifungal agents. The aim of this work was to isolate thionins from the kernels of the highly pathogen-resistant wheat species Triticum kiharae Dorof. et Migush., determine their primary structure, and assay antifungal activity against Candida albicans. For the first time from the wheat T. kiharae using chromatography on chitin and reversed-phase high-performance liquid chromatography (HPLC), 2 thionins Tk-AMP-BP and Tk-AMP-AP1 were isolated, and their amino acid sequences were determined by automated Edman degradation. The primary structure of Tk-AMP-BP was confirmed by transcriptome high-throughput sequencing (NGS) of wheat seedlings. The study of antimicrobial activity of Tk-AMP-BP showed that it has potent fungicidal effect on C. albicans cells at very low concentrations (MIC = 0.78 μg/ml). The biological activity of the wheat thionin against C. albicans was higher than that of thionins from other plant species. The results obtained in this work allow us to consider the wheat thionin as a promising molecule for the development on its basis of next-generation drugs to treat C. albicans infections.

Earlier, we discovered a gene family encoding hevein-like antimicrobial peptides (WAMP) in the highly resistant wheat species Triticum kiharae Dorof. et Migusch. and related species of the Triticum and Aegilops genera. These peptides suppress growth and development of fungi and bacteria by inhibition of secreted metalloproteinases of the pathogens. In this study, we analyzed wamp homologs in the wild cereal Elytrigia repens Desv. ex Nevski, which is an invasive weed. The wamp homologs were isolated by PCR with E. repens genomic DNA or cDNA and primers specific to the wheat wamp genes. The nucleotide sequences of three novel E. repenswamp genes encoding the precursors of the antimicrobial peptides named ERAMP-1, ERAMP-2 and ERAMP-3 were determined. The mature peptide regions of the precursors differed in single amino acid substitutions. It was shown that ERAMP-2 and ERAMP-3 have valine at position 34 affecting the degree of fungal proteinase inhibition, which has not been found in other WAMP homologs. To elucidate the role of the valine residue in the E. repens peptide antifungal activity, the recombinant peptide was expressed in E. coli and its antifungal activity was assayed against a range of phytopathogenic fungi belonging to ascomycetes. The peptide was more active than the wheat WAMP-1 peptide against three of four tested fungi infecting cereals and other plant species. The results obtained contribute to our knowledge of the biodiversity of wamp genes in Poaceae. In addition, they expand our understanding of the repertoire of defensive genes in E. repens responsible for its enhanced pathogen resistance.

Antimicrobial peptides (AMPs) are important components of defense system in both plants and animals. They represent an ancient mechanism of innate immunity providing rapid first line of defense against pathogens. Plant AMPs are classified into several families: thionins, defensins, nonspecific lipid-transfer proteins, hevein-and knottin-type peptides, hairpinins and macrocyclic peptides (cyclotides). The review focuses on the thionin family. Thionins comprise a plant-specific AMP family that consists of short (similar to 5 kDA) cysteine-rich peptides containing 6 or 8 cysteine residues with antimicrobial and toxic properties. Based on similarity in amino acid sequences and the arrangement of disulphide bonds, five structural classes of thionins are discriminated. The three-dimensional structures of a number of thionins were determined. The amphipathic thionin molecule resembles the Greek letter Gamma, in which the long arm is formed by two antiparallel alpha-helices, while the short one, by two parallel beta-strands. The residues responsible for the antimicrobial activity of thionins were identified. Thionins are synthesized as precursor proteins consisting of a signal peptide, the mature peptide region and the C-terminal prodomain. Thionins protect plants from pathogenic bacteria and fungi acting directly on the membranes of microorganisms at micromolar concentrations, although their precise mode of action remains unclear. In addition to plant pathogens, thionins inhibit growth of a number of human pathogens and opportunistic microorganisms, such as Candida spp., Saccharomyces cerevisiae, Fusarium solani, Staphylococcus aureus and Escherichia coli. Thionins are toxic to different types of cells including mammalian cancer cell lines. Transgenic plants expressing thionin genes display enhanced resistance to pathogens. A wide range of biological activities makes thionins promising candidates for practical application in agriculture and medicine.

Antimicrobial peptides (AMPs) constitute an important part of the plant immune system protecting plants from the invading pathogens. Some antimicrobial peptides are also active against human pathogenic microorganisms, including antibiotic-resistant strains that makes these molecules promising candidates for the design of next-generation drugs to treat infections. Plants represent a valuable source of effective yet poorly explored antimicrobial peptides. An efficient pipeline for highthroughput in silico detection of antimicrobial peptides in Lycopersicon esculentum genome has been developed. As many as 66 putative AMPs were revealed in L. esculentum genome. The discovered AMPs belong to four AMP families: defensins, thionins, lipid-transfer proteins, and hevein-type peptides. The vast majority of newly discovered peptides have not been annotated in L. esculentum genome so far. Further functional analysis of detected AMPs will evaluate their potential as novel drug leads and biopesticides for practical application in agriculture and medicine.

Plant extracts and microbial culture liquids contain a great number of bioactive substances, including potential biofungicides, which are effective against plant deseases.Screening of extracts and cultural filtrates for ability to suppress several pathogenic fungi that damage various agricultural plants can result in discovery of new compounds with a broad range of fungicidal activity.This work is the first report on in vitro testing the activity of plant extracts, which obtained by serial extractions of Chenopodium album seeds with hexane followed by ethyl acetate and then with ethanol, and also Fusarium sambucinum culture liquid filtrate (CLF), against six widespread fungi (Alternaria alternata, A. dauci, A. radicina, Bipolaris sorokiniana, Septoria tritici, Stagonospora nodorum) that are strongly pathogenic for several economically important crops.These fungi were found to demonstrate different sensitivity to CLF and seed extracts.Thus, CLFs with the activity level that was shown earlier for Stagonospora nodorum and A. radicina (effective dilutions up to 1:200 и 1:5, respectively) fully inhibited spore germination of all pathogens except B. sorokiniana, saving their antifugal activity to dilutions 1:5 (for A. dauci) or 1:50 (for Septoria tritici).Seed extracts possessed no toxicity against Stagonospora nodorum, Septoria tritici, A. dauci and A. radicina, but some of them reduced A. alternata and B. sorokiniana spore germination.For instance, after seed extraction with hexane followed by ethyl acetate, the number of germinated B. sorokiniana spores decreased by 66 % as compared to control.Hyphae of spores germinated in diluted CLF were morphologically defective and much shorter than control ones.Besides, a significant growth retardation of Stagonospora nodorum, Septoria tritici and B. sorokiniana mycelia was observed on agar media supplemented with CLF (100 μg/ml).Collectively, these results suggest that further research of CFL and the seed extracts can result in identification of anifungal metabolites, which could be promising as biofungicides against leaf and glume blotches of wheat, spot blotch or common root rot of other cereals, and Alternaria diseases of carrot.