Genome-Wide Identification of the Defensin Gene Family in Triticum durum and Assessment of Its Response to Environmental Stresses

Plant defensins (PDFs) are a group of cationic antimicrobial peptides that are distinguished by their unique tertiary structure and play significant roles in physiological metabolism, growth, and stress tolerance. Defensins are key components of plant innate immunity; they can target a wide variety of microorganisms. This study aimed to identify and investigate the role of Triticum durum PDFs (TdPDFs) in response to environmental stresses. Prior to this, in silico analyses of TdPDF genes were conducted to assess their chromosomal locations, conserved motifs, exon-intron distribution, and cis-regulatory elements in the promoter regions. Additionally, bioinformatic analyses were performed to characterize the structure of TdPDF proteins, evaluate their phylogenetic relationships, predict their subcellular localization, and estimate their physicochemical properties. Docking studies were conducted to assess the interactions between TdPDF proteins and the fungal plasma membrane. A total of 28 TdPDF genes were identified in durum wheat based on their conserved domain PF00304 (gamma-thionin). These genes are distributed across all chromosomes of the durum wheat genome, except for chromosomes 4A and 7A. Analysis of the promoters of these genes revealed numerous elements associated with development, hormone responsiveness, and environmental stress. The majority of TdPDF proteins were predicted to be located extracellular. In addition, TdPDF proteins were classified into three clusters based on sequence similarity. Phylogenetic analysis suggested that TdPDF proteins share ancestral similarities with the PDF sequences of other monocotyledonous species. Molecular docking studies revealed that TdPDF proteins interact with fungal plasma membranes, suggesting that they play a critical role in the resistance of plants to pathogen infections. Expression analysis underlined the crucial role of nine TdPDF genes in the defense responses of durum wheat against both pathogenic and environmental stressors. Overall, our findings underscore the potential of TdPDF genes in host-plant resistance and highlight opportunities for their application in crop improvement toward stress tolerance.

Plant secondary metabolites against biotic stresses for sustainable crop protection

Sustainable agriculture practices are indispensable for achieving a hunger-free world, especially as the global population continues to expand. Biotic stresses, such as pathogens, insects, and pests, severely threaten global food security and crop productivity. Traditional chemical pesticides, while effective, can lead to environmental degradation and increase pest resistance over time. Plant-derived natural products such as secondary metabolites like alkaloids, terpenoids, phenolics, and phytoalexins offer promising alternatives due to their ability to enhance plant immunity and inhibit pest activity. Recent advances in molecular biology and biotechnology have improved our understanding of how these natural compounds function at the cellular level, activating specific plant defense through complex biochemical pathways regulated by various transcription factors (TFs) such as MYB, WRKY, bHLH, bZIP, NAC, and AP2/ERF. Advancements in multi-omics approaches, including genomics, transcriptomics, proteomics, and metabolomics, have significantly improved the understanding of the regulatory networks that govern PSM synthesis. These integrative approaches have led to the discovery of novel insights into plant responses to biotic stresses, identifying key regulatory genes and pathways involved in plant defense. Advanced technologies like CRISPR/Cas9-mediated gene editing allow precise manipulation of PSM pathways, further enhancing plant resistance. Understanding the complex interaction between PSMs, TFs, and biotic stress responses not only advances our knowledge of plant biology but also provides feasible strategies for developing crops with improved resistance to pests and diseases, contributing to sustainable agriculture and food security. This review emphasizes the crucial role of PSMs, their biosynthetic pathways, the regulatory influence of TFs, and their potential applications in enhancing plant defense and sustainability. It also highlights the astounding potential of multi-omics approaches to discover gene functions and the metabolic engineering of genes associated with secondary metabolite biosynthesis. Taken together, this review provides new insights into research opportunities for enhancing biotic stress tolerance in crops through utilizing plant secondary metabolites.

The emerging role of cysteine-rich peptides in pollen-pistil interactions

Unlike early land plants, flowering plants have evolved a pollen tube that transports a pair of non-motile sperm cells to the female gametophyte. This process, known as siphonogamy, was first observed in gymnosperms and later became prevalent in angiosperms. However, the precise molecular mechanisms underlying the male-female interactions remain enigmatic. From the landing of the pollen grain on the stigma to gamete fusion, the male part needs to pass various tests: how does the stigma distinguish between compatible and incompatible pollen? what mechanisms guide the pollen tube towards the ovule? what factors trigger pollen tube rupture? how is polyspermy prevented? and how does the sperm cell ultimately reach the egg? Successful male-female communication is essential for surmounting these challenges, with cysteine-rich peptides (CRPs) playing a pivotal role in this dialogue. In this review, we summarize the characteristics of four distinct classes of CRPs, systematically review recent progress in the role of CRPs in four crucial stages of pollination and fertilization, consider potential applications of this knowledge in crop breeding, and conclude by suggesting avenues for future research.

Plant proteins, peptides, and non-protein amino acids: Toxicity, sources, and analysis

Plants have evolved various mechanisms to synthesize diverse range of substances that contribute to their survival against pests, pathogens, predators, and adverse environmental conditions. Although several plant metabolites possess therapeutic potential, some can be potentially harmful to human and animal health when consumed in large proportion. Proteins, peptides, and non-protein amino acids are products of plant biochemical pathways with proven beneficial and nutritional effects. Despite these benefits, the in vivo toxicities associated with certain plant-derived proteins, peptides, and non-protein amino acids pose a significant risk to humans and animals. Symptoms of poisoning include nausea, vomiting, diarrhea, hair and weight loss, goiter, cataracts, and infertility. Even though plant processing methods such as soaking and drying can reduce the amount of toxin contained in plants, complete riddance is often impossible. As such, food regulatory bodies need to prevent uncontrolled consumption of the listed and many other toxin-containing plant species to keep the public safe. For this purpose, this review collates crucial insights into the sources, and in vivo toxicity associated with certain plant-derived proteins, peptides, and non-protein amino acids that have the clear potential to adversely affect human health. Additionally, this review provides information on analytical methods suitable for the detection of these substances in plants.

Plant Antimicrobial Peptides (PAMPs): Features, Applications, Production, Expression, and Challenges

The quest for an extraordinary array of defense strategies is imperative to reduce the challenges of microbial attacks on plants and animals. Plant antimicrobial peptides (PAMPs) are a subset of antimicrobial peptides (AMPs). PAMPs elicit defense against microbial attacks and prevent drug resistance of pathogens given their wide spectrum activity, excellent structural stability, and diverse mechanism of action. This review aimed to identify the applications, features, production, expression, and challenges of PAMPs using its structure-activity relationship. The discovery techniques used to identify these peptides were also explored to provide insight into their significance in genomics, transcriptomics, proteomics, and their expression against disease-causing pathogens. This review creates awareness for PAMPs as potential therapeutic agents in the medical and pharmaceutical fields, such as the sensitive treatment of bacterial and fungal diseases and others and their utilization in preserving crops using available transgenic methods in the agronomical field. PAMPs are also safe to handle and are easy to recycle with the use of proteases to convert them into more potent antimicrobial agents for sustainable development.

Nigellothionins from Black Cumin (Nigella sativa L.) Seeds Demonstrate Strong Antifungal and Cytotoxic Activity

High-cationic biologically active peptides of the thionins family were isolated from black cumin (Nigella sativa L.) seeds. According to their physicochemical characteristics, they were classified as representatives of the class I thionin subfamily. Novel peptides were called “Nigellothionins”, so-called because of their source plant. Thionins are described as components of plant innate immunity to environmental stress factors. Nine nigellothionins were identified in the plant in different amounts. Complete amino acid sequences were determined for three of them, and a high degree of similarity was detected. Three nigellothionins were examined for antifungal properties against collection strains. The dominant peptide, NsW2, was also examined for activity against clinical isolates of fungi. Cytotoxic activity was determined for NsW2. Nigellothionins activity against all collection strains and clinical isolates varied from absence to a value comparable to amphotericin B, which can be explained by the presence of amino acid substitutions in their sequences. Cytotoxic activity in vitro for NsW2 was detected at sub-micromolar concentrations. This has allowed us to propose an alteration of the molecular mechanism of action at different concentrations. The results obtained suggest that nigellothionins are natural compounds that can be used as antimycotic and anti-proliferative agents.