Defensin Expression Research Articles

Transcriptome analysis of the allotetraploids of the Dilatata group of Paspalum (Poaceae): effects of diploidization on the expression of defensin and Snakin/GASA genes.

Plant Snakin/GASA and defensin peptides are cysteine-rich molecules with a wide range of biological functions. They are included within the large family of plant antimicrobial peptides (AMPs), characterized by their structural stability, broad spectrum of activity, and diverse mechanisms of action. The Dilatata group of Paspalum includes five allotetraploids that share an equivalent genomic formula IIJJ. From RNA-seq data of seedling tissues, we performed an in silico characterization of the defensin and Snakin/GASA genes in these species and diploids with a II and JJ genome formula and studied the evolutionary consequences of polyploidy on the expression of the two AMPs families. A total of 107 defensins (distributed in eight groups) and 145 Snakin/GASA (grouped in three subfamilies) genes were identified. Deletions, duplications and/or gene silencing seem to have mediated the evolution of these genes in the allotetraploid species. In defensin genes, the IIJJ allopolyploids retained the I subgenome defensin copies in some of the identified groups supporting the closeness of their nuclear genome with the I subgenome species. In both AMPs families, orthologous genes in tetraploids exhibit higher similarity to each other than with diploids. This data supports the theory of a single origin for the allotetraploids. Several copies of both defensin and Snakin/GASA genes were detected in the five polyploids which could have arisen due to duplication events occurring independently during the diploidization processes in the allotetraploid taxa.

Pioneering Clinical Investigation: Beta Defensin Expression in Patients of Squamous Cell Carcinoma of Oral Cavity as a Forward-Looking Validation for Molecular Treatment

Pioneering Clinical Investigation: Beta Defensin Expression in Patients of Squamous Cell Carcinoma of Oral Cavity as a Forward-Looking Validation for Molecular Treatment

Fatty acid synthase 2 knockdown alters the energy allocation strategy between immunity and reproduction during infection by Micrococcus luteus in Locusta migratoria

Immunity and reproduction are vital functions for the survival and population maintenance of female insects. However, owing to limited resources, these two functions cannot be fulfilled simultaneously, resulting in an energy tradeoff between them. Notably, the mechanisms underlying this immune-reproductive trade-off, in which energy competition likely plays a central role, remain poorly understood. Fatty acid synthase (FAS), a key gene involved in lipid synthesis and insect energy metabolism, was investigated in this study using Locusta migratoria as the research subject. Bacterial infection and RNA interference (RNAi) technology were used to examine changes in the immunity, fecundity, and energy metabolism patterns of locusts under different treatments. The findings of this study demonstrate that infection with Micrococcus luteus triggers an immune response in locusts, significantly upregulates the expression of defensin 3 (DEF3) and Attacin, and enhances pHenoloxidase (PO) activity. Upon FAS2 silencing, bacterial attack upregulated DEF3 and Attacin expression to a lesser extent, leading to increased lysozyme activity instead of PO. Furthermore, bacterial infection results in a decrease in glycogen and glucose content in the fat body, accompanied by a significant increase in triacylglycerol (TAG) content. However, after FAS2 knockdown, both the lipid and carbohydrate contents were significantly reduced in the fat body. Compared with bacterial infection alone, low FAS2 expression further exacerbated fecundity impairment in locusts. The expression levels of vitellogenin A (VgA) and vitellogenin B (VgB) were significantly low, with severe ovarian atrophy observed. Notably, the ovarian weight was only 21 % compared to that of the control group. Moreover, females exhibited minimal egg-laying behavior. In summary, our findings suggest that following FAS2 gene silencing, there is a greater inclination toward immune stimulation energy activation in locusts, whereas reproductive investment is reduced. The outcomes of this study will contribute to the further exploration of the molecular mechanisms underlying the trade-off between immune and reproductive energy in locusts.

Multigenerational expression of antimicrobial peptides in Aedes aegypti exposed to Metarhizium anisopliae: Is trans-generational immune priming involved?

We assessed, for the first time, a multigenerational expression of antimicrobial peptides (AMPs) in Aedes aegypti larvae exposed to the entomopathogenic fungus, Metarhizium anisopliae, and correlated it with a possible involvement in trans-generational immune priming (TGIP). Aedes aegypti larvae were first exposed to blastospores or conidia of M. anisopliae CG 489 for 24 and 48 h, and the relative expression of AMPs were measured using quantitative Real-Time PCR. A suspension of conidia was prepared, and two different survival tests were conducted with different larval generations (F0, F1, and F2). In the first bioassay, the survival curves of the three generations were conducted separately and compared with their respective control groups. In the other bioassay, the survival curves of the F0, F1, and F2 generations were compared simultaneously against a naïve group exposed to Tween 80. In both survival tests, the F0 generation was more susceptible to M. anisopliae than subsequent generations. For molecular analyses related to TGIP, F0, F1, and F2 larvae were exposed to conidia, and their expression of AMPs was compared with their control groups and a naïve group. There was no differential expression of cecropin, defensin A or cathepsin B between generations. Lysozyme C, however, showed an increase in expression across generations, suggesting a role in TGIP. These discoveries may help us develop biological insecticides against mosquito larvae based on entomopathogenic fungi.

Alterations in the gut microbiota of Eimeria infected broiler chickens fed diets supplemented with varying levels of dietary calcium and phosphorus, along with 25-hydroxycholecalciferol

The purpose of the study was to investigate the effects of the reduced dietary calcium (Ca) and phosphorus (P) level and supplementation of 25-hydroxycholecalciferol (25-OHD3) on the expression of vitamin D receptor (VDR) and antimicrobial peptides and gut microbiota of broiler chickens with/without Eimeria challenge. A total of 576 fourteen-day-old broiler chicks were randomly allocated according to a 2 × 2 × 2 factorial design with main effects including Eimeria challenging (125,000 Eimeria acervulina, 25,000 Eimeria maxima, and 25,000 Eimeria tenella), dietary Ca and P levels (0.84% Ca and 0.42% available P or 0.64% Ca and 0.22% available P), and supplementation of 25-OHD3 (3,000 IU/kg) of 6 replicates. Three-way ANOVA was performed, and the effects of 3 main factors and their interactions were investigated. The reduced dietary Ca and P level downregulated cathelicidins 3 (CATH3) in the upper jejunum in the Eimeria challenging condition (interaction; P < 0.05). The reduced dietary Ca and P level decreased the relative mRNA expression of jejunal avian beta defensin 5 (AvBD5) in the Eimeria challenging condition (interaction; P < 0.05). The reduced dietary Ca and P level tended to decrease the relative mRNA expression of jejunal AvBD9 in the Eimeria challenging condition (interaction; P = 0.051). The reduced dietary Ca and P level decreased observed features (alpha diversity parameter for richness) in the upper jejunal microbiota in the Eimeria challenging condition (interaction; P < 0.05). The supplementation of 25-OHD3 decreased the relative abundance of the phylum Bacteroidetes (P < 0.05) and increased the relative abundance of the family Ruminococcaceae (P < 0.05) in the cecal digesta. The supplementation of 25-OHD3 decreased the serum endotoxin level in the Eimeria challenging condition (interaction; P < 0.05). Therefore, the reduced dietary Ca and P level modulated the upper jejunal microbiota via modulating the expression of antimicrobial peptides, and the supplementation of 25-OHD3 favorably modulated the cecal microbiota in broiler chickens with/without Eimeria challenge.

A comprehensive characterization and expression profiling of defensin family peptides in Arabidopsis thaliana with a focus on their abiotic stress-specific transcriptional modulation

In addition to defensins, plants possess an array of defensin-like peptides that share many of their characteristics, as well as a role in plant’s innate immunity. Their involvement in the response to pathogens is well-known but the contribution in the plant response to abiotic stimuli is not fully understood. We have undertaken an in silico analysis to characterize all defensin family genes hitherto found in Arabidopsis, including genes encoding for defensin-like peptides, by detecting several peptides as candidates for further studies aiming to decipher specific responses to biotic and abiotic stresses, as well as to their crosstalk. We performed several analyses, including co-expression and cis-regulatory elements analyses, using transcriptomic data obtained from the ARS database, which integrates more than 20,000 Arabidopsis RNA-seq libraries.In silico analysis showed that jasmonates and ABA, together with transcription factors belonging to WRKY and AP2/EREBP families, modulate defensin and defensin-like gene expression. Indeed, the analysis performed in this study allowed to extract and organize omics data, which finally supported the inducible nature of defensins under both abiotic and biotic stresses. Moreover, in vivo expression analyses confirmed the heat and drought responsiveness of PDF1.4, ATTI1, PDF1.1, DEFL 206, defensin family genes selected for being upregulated by several abiotic conditions, at transcriptional level. Finally, the co-expression analysis provided information on other biological processes that may be correlated to the defensin induction, such as maintaining ROS homeostasis. Combining the comprehensive analysis of different transcriptional datasets with the integration of in vivo analyses emerged as a robust methodological approach to assess the proposed multi-stress responsive nature of defensin family genes.

Defensins: Exploring Their Opposing Roles in Colorectal Cancer Progression.

Colorectal cancer (CRC) represents a significant global healthcare burden, with a particularly concerning rising incidence among younger adults. This trend may highlight potential links between diet, gut microbiome, and CRC risk. Novel therapeutic options have been increasingly based on the understanding of molecular mechanisms and pathways. The PI3K/AKT/mTOR pathway, a crucial cell growth regulator, offers a promising target for CRC therapy. mTOR, a key component within this pathway, controls cell growth, survival, and metabolism. Understanding the specific roles of defensins, particularly human β-Defensin 1 (HBD-1), in CRC is crucial. HBD-1 exhibits potent antimicrobial activity and may influence CRC development. Deciphering defensin expression patterns in CRC holds the promise of improved understanding of tumorigenesis, which may pave the way for improved diagnostics and therapies. This article reviews recent advances in understanding regarding how HBD-1 influences CRC initiation and progression, highlighting the molecular mechanisms by which it impacts CRC. Further, we describe the interaction between defensins and mTOR pathway in CRC.

Biofilms and core pathogens shape the tumor microenvironment and immune phenotype in colorectal cancer

ABSTRACT Extensive research has explored the role of gut microbiota in colorectal cancer (CRC). Nonetheless, metatranscriptomic studies investigating the in situ functional implications of host-microbe interactions in CRC are scarce. Therefore, we characterized the influence of CRC core pathogens and biofilms on the tumor microenvironment (TME) in 40 CRC, paired normal, and healthy tissue biopsies using fluorescence in situ hybridization (FISH) and dual-RNA sequencing. FISH revealed that Fusobacterium spp. was associated with increased bacterial biomass and inflammatory response in CRC samples. Dual-RNA sequencing demonstrated increased expression of pro-inflammatory cytokines, defensins, matrix-metalloproteases, and immunomodulatory factors in CRC samples with high bacterial activity. In addition, bacterial activity correlated with the infiltration of several immune cell subtypes, including M2 macrophages and regulatory T-cells in CRC samples. Specifically, Bacteroides fragilis and Fusobacterium nucleatum correlated with the infiltration of neutrophils and CD4+ T-cells, respectively. The collective bacterial activity/biomass appeared to exert a more significant influence on the TME than core pathogens, underscoring the intricate interplay between gut microbiota and CRC. These results emphasize how biofilms and core pathogens shape the immune phenotype and TME in CRC while highlighting the need to extend the bacterial scope beyond CRC pathogens to advance our understanding and identify treatment targets.

Expression of defensin genes across house fly (Musca domestica) life history gives insight into immune system subfunctionalization.

Animals encounter diverse microbial communities throughout their lifetime, which exert varying selection pressures. Antimicrobial peptides (AMPs), which lyse or inhibit microbial growth, are a first line of defense against some of these microbes. Here we examine how developmental variation in microbial exposure has affected the evolution of expression and amino acid sequences of Defensins (an ancient class of AMPs) in the house fly (Musca domestica). The house fly is a well-suited model for this work because it trophically associates with varying microbial communities throughout its life history and its genome contains expanded families of AMPs, including Defensins. We identified two subsets of house fly Defensins: one expressed in larvae or pupae, and the other expressed in adults. The amino acid sequences of these two Defensin subsets form distinct monophyletic clades, and they are located in separate gene clusters in the genome. The adult-expressed Defensins evolve faster than larval/pupal Defensins, consistent with different selection pressures across developmental stages. Our results therefore suggest that varied microbial communities encountered across life history can shape the evolutionary trajectories of immune genes.

Reduced expression of central innate defense molecules in pancreatic biopsies from subjects with Type 1 diabetes

Aims/HypothesisDefensins play a crucial role in the innate immune system's first defense against microbial threats. However, little is known about the defensin system in the pancreas, especially in relation to Type 1 diabetes. We explore the expression of defensins in different disease stages of Type 1 diabetes and correlated obtained findings to the degree of inflammation, providing new insights into the disease and the innate immune system.Material and methodsPancreases from non-diabetic human organ donors of different age groups and donors with Type 1 diabetes with different disease duration were examined. Sections from head, body and tail of the pancreas were stained for eight different defensins and for immune cells; CD3+, CD45+, CD68+ and NES+ (granulocytes).ResultsIn non-diabetic adult controls the level of expression for defensins Beta-1,Alpha-1, Cathelicidin and REG3A correlated with the level of inflammation. In contrast, individuals with Type 1 diabetes exhibit a reduction or absence of several central defensins regardless of the level of inflammation in their pancreas. The expression of Cathelicidin is present in neutrophils and macrophages but not in T-cells in subjects with Type 1 diabetes.ConclusionsObtained findings suggest a pancreatic dysfunction in the innate immune system and the bridging to the adaptive system in Type 1 diabetes. Further studies on the role of the local innate immune system in Type 1 diabetes is needed.

Change in Tissue Microbiome and Related Human Beta Defensin Levels Induced by Antibiotic Use in Bladder Carcinoma.

It is now generally accepted that the success of antitumor therapy can be impaired by concurrent antibiotic therapy, the presence of certain bacteria, and elevated defensin levels around the tumor tissue. The aim of our current investigation was to identify the underlying changes in microbiome and defensin levels in the tumor tissue induced by different antibiotics, as well as the duration of this modification. The microbiome of the tumor tissues was significantly different from that of healthy volunteers. Comparing only the tumor samples, no significant difference was confirmed between the untreated group and the group treated with antibiotics more than 3 months earlier. However, antibiotic treatment within 3 months of analysis resulted in a significantly modified microbiome composition. Irrespective of whether Fosfomycin, Fluoroquinolone or Beta-lactam treatment was used, the abundance of Bacteroides decreased, and Staphylococcus abundance increased. Large amounts of the genus Acinetobacter were observed in the Fluoroquinolone-treated group. Regardless of the antibiotic treatment, hBD1 expression of the tumor cells consistently doubled. The increase in hBD2 and hBD3 expression was the highest in the Beta-lactam treated group. Apparently, antibiotic treatment within 3 months of sample analysis induced microbiome changes and defensin expression levels, depending on the identity of the applied antibiotic.

Defensins of the stable fly (Stomoxys Calcitrans) have developmental-specific regulation and evolve at different rates.

Organisms produce antimicrobial peptides (AMPs) either in response to infection (induced) or continuously (constitutively) to combat microbes encountered during normal trophic activities and/or through pathogenic infections. The expression of AMPs is tightly regulated often with specificity to particular tissues or developmental stages. As a result, AMPs face varying selective pressures based on the microbes the organism's tissue or developmental stage encounters. Here, we analyzed the evolution and developmental-specific expression of Defensins, which are ancient AMPs in insects, in the stable fly (Stomoxys calcitrans). Stable fly larvae inhibit microbe-rich environments, whereas adult flies, as blood-feeders, experience comparatively fewer encounters with diverse microbial communities. Using existing RNA-seq datasets, we identified six Defensins that were only expressed in larvae (larval Defensins) and five that were not expressed in larvae (non-larval Defensins). Each of the non-larval Defensins was expressed in at least one adult tissue sample. Half of the larval Defensins were induced by mating or feeding in adults, and all three of the induced Defensins were located downstream of canonical binding sites for an Imd transcription factor involved in the highly conserved NF-κB signaling that regulates induction of AMPs. The larval and non-larval Defensins were located in distinct genomic regions, and the amino acid sequences of the larval Defensins formed a monophyletic clade. There were more amino acid substitutions across non-larval Defensins, with multiple genes losing a highly conserved furin cleavage site thought to be required for the removal of the amino terminus from the mature Defensin domain. However, larval Defensins had a higher proportion of radical amino acid substitutions, altering amino acid size and polarity. Our results reveal insights into the developmental stage-specific regulation of AMPs, and they suggest different regulatory regimes impose unique selection pressures on AMPs, possibly as a result of variation in exposure to microbial communities across development.

The transcriptional response in mosquitoes distinguishes between fungi and bacteria but not Gram types

Mosquitoes are prolific vectors of human pathogens, therefore a clear and accurate understanding of the organization of their antimicrobial defenses is crucial for informing the development of transmission control strategies. The canonical infection response in insects, as described in the insect model Drosophila melanogaster, is pathogen type-dependent, with distinct stereotypical responses to Gram-negative bacteria and Gram-positive bacteria/fungi mediated by the activation of the Imd and Toll pathways, respectively. To determine whether this pathogen-specific discrimination is shared by mosquitoes, we used RNAseq to capture the genome-wide transcriptional response of Aedes aegypti and Anopheles gambiae (s.l.) to systemic infection with Gram-negative bacteria, Gram-positive bacteria, yeasts, and filamentous fungi, as well as challenge with heat-killed Gram-negative, Gram-positive, and fungal pathogens. From the resulting data, we found that Ae. aegypti and An. gambiae both mount a core response to all categories of infection, and this response is highly conserved between the two species with respect to both function and orthology. When we compared the transcriptomes of mosquitoes infected with different types of bacteria, we observed that the intensity of the transcriptional response was correlated with both the virulence and growth rate of the infecting pathogen. Exhaustive comparisons of the transcriptomes of Gram-negative-challenged versus Gram-positive-challenged mosquitoes yielded no difference in either species. In Ae. aegypti, however, we identified transcriptional signatures specific to bacterial infection and to fungal infection. The bacterial infection response was dominated by the expression of defensins and cecropins, while the fungal infection response included the disproportionate upregulation of an uncharacterized family of glycine-rich proteins. These signatures were also observed in Ae. aegypti challenged with heat-killed bacteria and fungi, indicating that this species can discriminate between molecular patterns that are specific to bacteria and to fungi.

Understanding the Dynamics of Human Defensin Antimicrobial Peptides: Pathogen Resistance and Commensal Induction.

Antimicrobial peptides (AMPs), also known as host defense peptides, are petite molecules with inherent microbicidal properties that are synthesized by the host's innate immune response. These peptides serve as an initial barrier against pathogenic microorganisms, effectively eliminating them. Human defensin (HD) AMPs represent a prominent group of peptides involved in the innate immune response of humans. These peptides are primarily produced by neutrophils and epithelial cells, serving as a crucial defense mechanism against invading pathogens. The extensive research conducted has focused on the broad spectrum of antimicrobial activities and multifaceted immunomodulatory functions exhibited by human defensin AMPs. During the process of co-evolution between hosts and bacterial pathogens, bacteria have developed the ability to recognize and develop an adaptive response to AMPs to counterattack their bactericidal activity by different antibiotic-resistant mechanisms. However, numerous non-pathogenic commensal bacteria elicit the upregulation of defensins as a means to surmount the resistance mechanisms implemented by pathogens. The precise mechanism underlying the induction of HD by commensal organisms remains to be fully understood. This review summarizes the most recent research on the expression of human defensin by pathogens and discusses the various defense mechanisms used by pathogens to counter host AMP production. We also mention recent developments in the commensal induction of defensin AMPs. A better knowledge of the pathogens' defensin AMP resistance mechanisms and commensals' induction of AMP expression may shed light on the creation of fresh antibacterial tactics to get rid of bacterial infection.

Effect of Supplementation with Curcuma longa and Rosmarinus officinalis Extract Mixture on Acute Phase Protein, Cathelicidin, Defensin and Cytolytic Protein Gene Expression in the Livers of Young Castrated Polish White Improved Bucks.

Goats are an excellent animal model for research on some physiological and pathophysiological processes in humans. The search for supplements that prevent homeostasis disorders and strengthen the immune system is necessary to reduce the risk of many diseases in both humans and animals. The aim of the study was to analyze the effect of supplementation with a mixture of dried extracts of Curcuma longa and Rosmarinus officinalis on the expression of acute-phase protein (SAA, HP, CRP, LALBA, AGP, CP, FGA, FGB, and FGG), cathelicidin (BAC5, BAC7.5, BAC3.4, MAP28, MAP34, and HEPC), beta-defensin-1 (GBD1, DEFB1), and beta-defensin-2, and cytolytic protein (LIZ and LF) genes in the livers of young castrated bucks of the Polish White Improved breed. The higher expression of LF in the control group suggests that it is important for the first line of hepatic immune defense and its expression is downregulated by the mixture of turmeric and rosemary extracts; thus, the spice-herb mixture mutes its activity. The lower expression of FGB and the higher expression of BAC5 genes in the livers of healthy, young castrated bucks who were administered the supplement suggest the silencing effects of the mixture on the acute-phase response and the stimulating effect on the antimicrobial activity of the immune system.

Dietary propionate administration improves growth performance, hepatic lipid deposition, and intestinal activity of digestive enzymes, inflammation, bacterial population, and antioxidant capacity in rainbow trout, Oncorhynchus mykiss

The present study aimed to investigate the effects of dietary sodium propionate on growth performance, hepatic lipid deposition, and intestinal activity of digestive enzymes, inflammation, bacterial population, and antioxidant capacity in rainbow trout, Oncorhynchus mykiss. The fish were fed diets supplemented with 0 g/kg (CTL), 1 g/kg (P1), 2.5 g/kg (P2.5), or 5 g/kg (P5) sodium propionate for 70 days. The results showed significant (P < 0.05) linear or quadratic relationships between dietary sodium propionate levels and all tested parameters. Growth performance and feed efficiency significantly increased in the P1 and P2.5 treatments, but decreased in the P5 treatment, compared to the CTL group. Hepatosomatic index significantly decreased in the P1 and P2.5 treatments, but increased in the P5 treatment, compared to the CTL group. The P1 and P2.5 treatments exhibited significantly lower viscerosomatic indices than the CTL group. The P1 and/or P2.5 treatments exhibited significantly higher intestinal amylase, lipase, trypsin, chymotrypsin, superoxide dismutase (SOD), catalase (CAT), and lower intestinal malondialdehyde (MDA), plasma glucose, and triglyceride levels than the CTL treatment. On the other hand, the P5 treatment exhibited significant decrease in intestinal lipase, SOD, CAT, and higher intestinal MDA, plasma glucose, cortisol, triglyceride, and cholesterol levels than the CTL group. The intestinal total viable bacteria significantly decreased in the propionate treatments, and the lowest level was observed in the P2.5 treatment. The P1 and P2.5 treatments had significantly higher intestinal abundance of Lactobacillus sp. and lower Aeromonas hydrophila, Yersinia ruckeri, and Streptococcus iniae than the CTL group. The pathogenic bacteria showed significant elevations in the P5 treatment, compared to the CTL group. The propionate treatment groups showed significant up-regulations in intestinal heat shock protein 70 expression than the CTL group. The intestinal expression of tumor necrosis factor-alpha and interleukin-1 beta significantly decreased in the P1 and P2.5 treatments, while increased in the P5 treatment, compared to the CTL group. The intestinal expression of defensin significantly increased in the P1 and P2.5 treatments, while decreased in the P5 treatment, compared to the CTL group. In conclusion, dietary sodium propionate can improve the growth and intestinal health of rainbow trout. Based on the results, 2.5 g/kg sodium propionate is suitable for rainbow trout, but higher levels induce growth retardation, hepatic lipid accumulation, and intestinal oxidative stress, inflammation, and dysbiosis.

Filipendula glaberrima Nakai extract inhibits the bacterial infection by induction of HBD2 and HBD3 expression, and reduction of the inflammatory activity.

Defensins and inflammation are innate immune barriers of the body against infectious pathogens. Searching for a compound that can inhibit infectious diseases by affecting human β-defensin (HBD) and proinflammatory cytokines is the new trend in research to control bacterial infection. The aim of this study is to provide a natural compound, Filipendula glaberrima Nakai extract (FGE), which is able to induce the expression of an antimicrobial defensin as well as reduce inflammation. FGE induced the expression of HBD2 and HBD3 through activating both p38 and NF-κB signaling pathways. Furthermore, FGE inhibited the expression of TNF-α and IL-6 via p38 and NF-κB pathways in Staphylococcus aureus-stimulated THP1 cells. Injection of FGE alleviated cutaneous erythema and swelling caused by S. aureus injection in mice ears. Taken together, FGE could reduce bacterial infection by inducing the expression of defensin and anti-inflammatory activity.

Reduction in PLANT DEFENSIN 1 expression in Arabidopsis thaliana results in increased resistance to pathogens and zinc toxicity.

Ectopic expression of defensins in plants correlates with their increased capacity to withstand abiotic and biotic stresses. This applies to Arabidopsis thaliana, where some of the seven members of the Plant Defensin 1 family (AtPDF1) are recognised to improve plant responses to necrotrophic pathogens and increase seedling tolerance to excess zinc (Zn). However, few studies have explored the effects of decreased endogenous defensin expression on these stress responses. Here, we carried out an extensive physiological and biochemical comparative characterisation of i) novel amiRNA lines silenced for the five most similar AtPDF1s, and ii) a double null mutant for the two most distant AtPDF1s. Silencing of five AtPDF1 genes was specifically associated with increased aboveground dry mass production in mature plants under Zn excess conditions, and with increased plant tolerance to different pathogens - one fungus, one oomycete and one bacterium, while the double mutant behaved similarly to the WT. These unexpected results challenge the current paradigm describing the role of PDFs in the plant response to stresses. Additional roles of plant endogenous defensins are discussed, which open new perspectives for their functions.

Characterization and expression of fungal defensin in Escherichia coli and its antifungal mechanism by RNA-seq analysis.

Invasive fungal infections (IFIs) are fatally threatening to critical patients. The fungal defensin as an antifungal protein can widely inhibit fungi. In this study, eight antifungal genes from different filamentous fungi were optimized by synonymous codon bias and heterologously expressed in Escherichia coli. Only the antifungal protein (AFP) from Aspergillus giganteus was produced, whereas the AFP from its mutation of the chitin-binding domain could not be expressed, thereby suggesting the importance of the motif for protein folding. In addition, the recombinant AFP (rAFP, 100 μg/mL) pre-heated at 50°C for 1 h effectively inhibited Paecilomyces variotii CICC40716 of IFIs by 55%, and no cell cytotoxicity was observed in RAW264.7 cells. After being pre-heated at 50°C for 8 h, the fluorescence emission intensity of the rAFP decreased and shifted from 343 nm to 335 nm. Moreover, the helix and β-turn of the rAFP gradually decreased with the pre-heated treatment temperature of 50°C via circular dichroism spectroscopy. Propidium iodide staining revealed that the rAFP could cause damage to the cell membrane. Moreover, the corresponding differentially expressed genes (DEGs) for downregulation such as amino sugar and nucleotide sugar metabolism, as well as mitogen-activated protein kinase (MAPK) signaling pathway involved in the cell wall integrity were found via the RNA-seq of rAFP treatment. By contrast, the upregulated DEGs were enriched in response to the oxidative stress of Biological Process by the Gene Ontology (GO) database. The encoding proteins of laccase, multicopper oxidase, and nitroreductase that contributed to reactive oxygen species (ROS) scavenging could be recognized. These results suggested that the rAFP may affect the integrity of the cell wall and cell membrane, and promote the increase in ROS, thereby resulting in fungal death. Consequently, drug development could be based on the inhibitory effect of the rAFP on IFIs.

Exploring the potential role of defensins in differential vector competence of body and head lice for Bartonella quintana

BackgroundThe body and head lice of humans are conspecific, but only the body louse functions as a vector to transmit bacterial pathogens such as Bartonella quintana. Both louse subspecies have only two antimicrobial peptides, defensin 1 and defensin 2. Consequently, any differences in the molecular and functional properties of these two louse subspecies may be responsible for the differential vector competence between them.MethodsTo elucidate the molecular basis of vector competence, we compared differences in the structural properties and transcription factor/microRNA binding sites of the two defensins in body and head lice. Antimicrobial activity spectra were also investigated using recombinant louse defensins expressed via baculovirus.ResultsThe full-length amino acid sequences of defensin 1 were identical in both subspecies, whereas the two amino acid residues in defensin 2 were different between the two subspecies. Recombinant louse defensins showed antimicrobial activities only against the representative Gram-positive Staphylococcus aureus but not against either Gram-negative Escherichia coli or the yeast Candida albicans. However, they did show considerable activity against B. quintana, with body louse defensin 2 being significantly less potent than head louse defensin 2. Regulatory sequence analysis revealed that the gene units of both defensin 1 and defensin 2 in body lice possess decreased numbers of transcription factor-binding sites but increased numbers of microRNA binding sites, suggesting relatively lower transcription activities of body louse defensins.ConclusionsThe significantly lower antibacterial activities of defensin 2 along with the reduced probability of defensin expression in body lice likely contribute to the relaxed immune response to B. quintana proliferation and viability, resulting in higher vector competence of body lice compared to head lice.Graphical