Important Defense Research Articles

The Chiefs of Staff Committee and Continental Air Defence, 1954–60: How Not to Manage Defence Policy

The place of the military in the development of defence policy has long been a problem to Canada’s central organization for defence. While the primacy of civilian politicians has never been in doubt, the organization of military input to decision-making has been revised several times and remains in question. In 1947, Defence Minister Brooke Claxton reorganized the Canadian central organization for defence by creating the Chiefs of Staff Committee (csc), appointing a permanent chairman, Lieutenant-General Charles Foulkes, in 1951. While some historians have considered the csc’s “Command Age” to have been a golden one, recent analyses have been more critical but have not assessed the csc as an institution. This article looks in depth at the csc’s management of continental air defence during the 1950s and 1960s – Canada’s single most important defence project. It argues that the csc failed to provide objective advice to ministers. Under Foulkes, it carefully edited analyses submitted to Cabinet, manipulated reviews, and suppressed dissent in order to support its preferred manned interceptor option. As a result, the ministers and the senior public service lost confidence in the armed services, setting the stage for a massive reorganization in the 1960s that was aimed at strengthening the role of civilians in defence policy.

Resource supply and demand model of military settlements in the cold weapon era: case of Zhenbao Town, Ming Great Wall

As an important military defense project in Chinese history, the Ming Dynasty Great Wall and its associated military settlements played a crucial role in maintaining border security. A systematic analysis of how military settlements allocated resources based on external threats and geo-strategic needs is essential to understanding their settlements defense systems. However, this aspect has been relatively under-explored in existing research. Therefore, a resource allocation assessment model for Great Wall military settlements during the Cold Weapon era is established to facilitate a more scientific analysis and quantitative assessment of Military Defense Capabilities(MDC) and Military Requirements(MR). This study employs a combined Analytical Hierarchy Process (AHP) and Principal Component Analysis (PCA) approach to determine the weight of each indicator for both military defense capability and military requirement. Spatial clustering using K-means is conducted to visualize the distribution of these strengths and weaknesses. An Ordinary Least Squares (OLS) regression model links military requirements with defense capabilities, assessing the relationship between settlement locations and historical battle sites. Residual analysis is utilized to identify areas of resource over-allocation or under-allocation. The study reveals that the regional differences in military defense capabilities and requirements within the Zhenbao Town area during the Ming Dynasty correspond closely with the locations of frequent conflicts. This finding suggests that the distribution of defensive capabilities were strengthened in areas with challenging terrain, while the effectiveness and allocation of defense capabilities were determined by logistical support and transportation conditions. This study enhances our understanding of historical military strategies from a historical geography perspective and offers innovative insights for analyzing Great Wall settlement, moving beyond mere sensory intuition and historical experience.

Haploid-Phased Chromosomal Telomere-to-Telomere Genome Assembly of Medicinal Plant Uncaria rhynchophylla Dissects Genetic Controls on the Biosynthesis of Bioactive Alkaloids.

Natural indole alkaloids provide important medicinal resources and defences to environmental stresses. The Uncaria genus is a recorded traditional medicinal woody plant with high alkaloids. Genomic insights into alkaloid variation remain elusive. Here, we have dissected the haploid-resolved chromosomal T2T genome assembly of Uncaria rhynchophylla with a size of ~634 Mb and contig N50 of 27 Mb using PacBio HiFi long-reads plus Hi-C reads and anchored the contigs on 22 pairs of confirmed chromosomes. This genome contains 56% repeat sequences and ~29 000 protein-encoding genes. U. rhynchophylla diverged from a common ancestor shared with Coffea around 20 million years ago and contains expanded and contracted gene families associated with secondary metabolites and defences/resistance to stresses. We constructed the pathway and mined genes for rhynchophylline alkaloid biosynthesis. Fifty-three alkaloids in this pathway and eight differentially expressed genes are the keys to alkaloid accumulation. Elevated alkaloid levels are driven by high copy numbers of critical genes STRs and SGRs involved in strictosidine synthesis and hydrolysis as evidenced by phylogenetic, expression and RNA interference analyses. These results advance our genetic understanding and guide further breeding improvements, stress adaptation studies and pharmaceutical development.

Tetracycline and Oxacillin Act Synergistically on Biofilms and Display Increased Efficacy In Vivo Against Staphylococcus aureus.

Oxacillin (bactericidal) and tetracycline (bacteriostatic) are clinically relevant antibiotics that are routinely prescribed to treat Staphylococcus aureus infections but not conventionally used in combination. There is an urgent need for treatment regimens that can act upon biofilms during infection, associated with chronic infections on indwelling devices, as well as acute planktonic (systemic) infection. Here we show that in an in vitro model oxacillin and tetracycline act synergistically against S. aureus UAMS-1 biofilms, reducing the concentration of both antibiotics necessary to eradicatean established biofilm. Using an in vivo zebrafish larval infection model with S. aureus NewHG, they display improved bacterial clearance compared to each drug alone and can counteract a loss of host phagocytes, an important innate defence against S. aureus. In these cases, the bacteriostatic nature of tetracycline enhances rather than dampens the bactericidal action of oxacillin, although an exact mechanism remains to be elucidated. We suggest a dual therapy could be of clinical use against biofilm-forming S. aureus and has a potential use in patients with a compromised immune system.

The antibacterial defence role of β-defensin in the seahorse testis

Seahorses represent the only known group of animals with male pregnancy. Seahorses have small testis that produce a limited quantity of sperm. To date, the response of this immune-privileged organ to pathogenic infections has not been reported. β-defensin (BD) is an important innate immune defence factor against pathogens in vertebrate testis. To elucidate its immunoprotection in seahorse testis, we identified the Hippocampus erectus β-defensin (HeBD) sequence in its genome via phylogenetic tree and protein-sequence structure analysis. Gene-expression analysis showed that HeBD was highly expressed in the seahorse testis and was significantly upregulated after bacterial infection, indicating that HeBD expression was related to testicular immune responses. Furthermore, antibacterial activity testing demonstrated that the mature HeBD peptide exhibited broad-spectrum aggregation activity but only moderate antibacterial activity. We found that the mature HeBD mature significantly neutralised bacterial endotoxin activity. In conclusion, our results imply that HeBD serves an immunoprotective role in seahorse testis.

Independent evolution of plant natural products: Formation of benzoxazinoids in Consolida orientalis (Ranunculaceae)

Benzoxazinoids (BXDs) are important defense compounds produced by a number of species from different, evolutionarily unrelated plant families. While BXD biosynthesis has been extensively studied in the grasses (monocots) and core eudicots, the mechanism of BXD synthesis in the basal eudicots is still unclear. We used an integrated metabolomics and transcriptomics approach to elucidate the BXD pathway in Consolida orientalis, a Ranunculaceae species known to produce the BXD DIBOA-Glc. Overexpression of candidate genes in Nicotiana benthamiana identified a flavin-dependent monooxygenase (CoBX2-3) and two cytochrome P450 enzymes (CoBX4 and CoBX5) that catalyze the oxidation steps that transform indole into DIBOA. Co-expression of CoBx2-3, CoBx4, and CoBx5 with the previously described indole synthase gene CoBx1 and the UDP-glucosyltransferase gene CoBx8 in N. benthamiana resulted in the reconstitution of a fully active BXD pathway. The fact that CoBX2-3, CoBX4, and CoBX5 are not phylogenetically related to their counterparts in the grasses and core eudicots suggests independent evolution of benzoxazinoids biosynthesis in these three angiosperm lineages.

Role of Aralkylamine N-Acetyltransferase in the Response to Antioxidative Stress in the Fruit Fly Drosophila Melanogaster Adults.

In multicellular organisms, the indole melatonin synthesized by aralkylamine N-acetyltransferase (AANATI) serves as an antioxidant. To test this, sex-mixed 3-day-old mated fly adults bw1 and AANAT1 homozygous recessive loss-of-function mutant (bw AANAT1lo) of Drosophila melanogaster were fed by a standard diet or by one containing paraquat (PQ, 1,1'-dimethyl-4,4'-bipyridilium dichloride hydrate) at a final concentration of 15.5 mM. Experiment lasted 8 h and began at 11 a.m. In bw1 flies the paraquat treatment resulted in a significant (evaluated by Student's t-tests) decrease of the superoxide dismutase (SOD) activity and an increase the catalase (CAT) and glutathione S-transferase (GST) activities. Meanwhile, in these flies, total Antioxidative capacity (TAC) was significantly curbed by the paraquat presence. Importantly, these changes were not observed in the AANAT1-mutants. Thus, melatonin seems to play an important defence role against the oxidative stress elicited by paraquat.

The clinical praxis of bacteriocins as natural anti-microbial therapeutics.

In recent decades, the excessive use of antibiotics has resulted in a rise in antimicrobial drug resistance (ADR). Annually, a significant number of human lives are lost due to resistant infectious diseases, leading to around 700,000 deaths, and it is estimated that by 2050, there could be up to 10 million casualties. Apart from their possible application as preservatives in the food sector, bacteriocins are gaining acknowledgment as potential clinical treatments. Not only this, these antimicrobial peptides have revealed in modulating the host immune system producing anti-inflammatory and anti-modulatory responses. At the same time, due to the ever-increasing global threat of antibiotic resistance, bacteriocins have gained attraction among researchers due to their potential clinical applications. Bacteriocins as antimicrobial peptides, represent one of the most important natural defense mechanisms among bacterial species, particularly lactic acid bacteria (LAB), that can fight against infection-causing pathogens. In this review, we are highlighting the potential of bacteriocins as novel therapeutics for inhibiting a wide range of clinically relevant and multi-drug-resistant pathogens (MDR). We also highlight the effectiveness and potential applications of current bacteriocin treatments in combating antimicrobial resistance (AMR), thereby promoting human health.

Yeast encapsulation of photosensitive insecticides increases toxicity against mosquito larvae while protecting microorganisms

An important defense against the deadly diseases that mosquitoes transmit is the application of insecticides that reduce mosquito populations. Unfortunately, the evolution and subsequent spread of insecticide resistance has decreased their efficacy. Therefore, new mosquito control strategies are needed. One class of larvicides, known as photosensitive insecticides, or PSIs, kills larvae via light-activated oxidative damage. PSIs are promising larvicides because of their high larvicidal efficacy, rapid photodegradation, inexpensive cost, and mechanism that is dissimilar to other insecticide classes. We explored a novel delivery strategy for increasing both the larvicidal efficiency and environmental biocompatibility of PSIs, known as yeast encapsulation. Using the PSIs, curcumin and methylene blue, we measured the survival of Anopheles gambiae larvae and Escherichia coli following exposure to either non-encapsulated or yeast-encapsulated PSIs and a photoperiod. Yeast encapsulation increased the phototoxicity of both curcumin and methylene blue against mosquito larvae, likely by increasing ingestion. Furthermore, yeast encapsulation protected E. coli from the phototoxicity of yeast-encapsulated curcumin, but not yeast-encapsulated methylene blue. Yeast encapsulation increases the larvicidal efficacy of a PSI while also increasing biocompatibility. Therefore, yeast encapsulation of PSIs is a promising insecticide delivery strategy for mosquito control.

GmWRKY33A positively regulates disease resistance in soybean (Glycine max)

The WRKY transcription factor gene family is a plant-specific transcription factor that plays important roles defense responses. Studies in model plant Arabidopsis demonstrated that WRKYs function downstream of mitogen activated-protein kinase (MAPK) signaling cascade and participate in defense responses through activating the expression of defense-related genes. However, the roles of WRKYs in defense responses have not been previously investigated in paleopolyploidy soybean. Bioinfomatic analysis revealed that there are three pair of GmWRKY33 genes in the soybean genome. The identity of first two pair of GmWRKY33 genes is greater than 84% (named as GmWRKY33A). The identity of genes within the same pair is greater than 95%. A 300 bp fragment highly homologous to these four GmWRKY33A was chosen to clone into bean pod mosaic virus (BPMV)-based silencing vector (BPMV-VIGS) to achieve the goal of silencing four GmWRKY33A genes simultaneously. In this study, we simultaneously silenced four homologous genes of GmWRKY33A using a bean pod mottle virus (BPMV) vector carrying a single fragment of GmWRKY33A. Comparing the silenced plants with the vector control plants, no evident morphological phenotypes were observed. However, the GmWRKY33A-silenced plants exhibited significantly reduced resistance to Pseudomonas syringae pv. glycinea (Psg), Xanthomonas axonopodis pv. glycine (Xag), as well as to soybean mosaic virus (SMV). Furthermore, we demonstrated that silencing these GmWRKY33A genes significantly inhibited the activation of GmMPK3/GmMPK6 induced by Psg infection. Collectively, our results suggest that GmWRKY33As are involved in soybean immunity through regulating the transcription of GmMPK3/6 genes or activating the kinase activities of GmMPK3/6. Taken together, our results demonstrated that GmWRKY33As are positive regulators of soybean immune responses.

CRISPR-Cas systems in enterococci.

Enterococci are members of the microbiota of humans and other animals. They can also be found in the environment, associated with food, healthcare infections, and hospital settings. Due to their wide distribution, they are inserted in the One Health context. The selective pressure caused by the extensive use of antimicrobial agents in humans, animals, and agriculture has increased the frequency of resistance to various drugs among enterococcal species. CRISPR-Cas system, an important prokaryotic defense mechanism against the entry of mobile genetic elements, may prevent the acquisition of genes involved in antimicrobial resistance and virulence. This system has been increasingly used as a gene editing tool, which can be used as a way to recognize and inactivate genes of interest. Here, we conduct a review on CRISPR systems found in enterococci, considering their occurrence, structure and organization, mechanisms of action and use as a genetic engineering technology. Type II-A CRISPR-Cas systems were shown to be the most frequent among enterococcal species, and the orphan CRISPR2 was the most commonly found system (54.1%) among enterococcal species, especially in Enterococcus faecalis. Distribution of CRISPR systems varied among species. CRISPR systems had 1 to 20 spacers, with size between 23 and 37bp and direct repeat sequences from 25 to 37bp. Several applications of the CRISPR-Cas biotechnology have been described in enterococci, mostly in vitro, using this editing tool to target resistance- and virulence-related genes.

When Influencers Compare Brands: Defensive Processing of Sponsored Comparative Messages and Effects on Consumer Evaluations

Social media influencers comparing competing products helps draw the desirable consumer attention to their product recommendation. However, it may also risk backfiring, especially when the influencer post is sponsored by a given brand. In the present study, we explored consumer evaluations of sponsored influencer comparative marketing through two important defensive mechanisms—counterarguing and inferences of manipulative intent with a 2 (message appeal: noncomparative vs. comparative) × 2 (content sponsorship: organic vs. sponsored) between-subjects online experiment (N = 325). We found that when the post was sponsored, the comparative message generated significantly greater defensive reactions than the noncomparative message, leading to lower perceived trustworthiness and authenticity of the influencer, unfavorable brand attitude, and lower purchase intention. In contrast, when the post was organic, the observed difference diminished. Furthermore, we found more prominent effects via inferences of manipulative intent than counterarguing, suggesting that consumers considerably value the genuineness behind product promotion from influencers. These findings extend research on comparative advertising to the trending influencer marketing context, shedding novel light on mechanisms underlying consumer responses to sponsored comparative messaging.

Pangolin scales as adaptations for innate immunity against pathogens

BackgroundPangolins are the only mammals that have overlapping scales covering most of their bodies, and they play a crucial role in the ecosystem, biological research, and human health and disease. Previous studies indicated pangolin scale might provide an important mechanical defense to themselves. The origin and exact functions of this unique trait remain a mystery. Using a multi-omics analysis approach, we report a novel functional explanation for how mammalian scales can provide host–pathogen defense.ResultsOur data suggest that pangolin scales have a sophisticated structure that could potentially trap pathogens. We identified numerous proteins and metabolites exhibiting antimicrobial activity, which could suggest a role for scales in pathogen defense. Notably, we found evidence suggesting the presence of exosomes derived from diverse cellular origins, including mesenchymal stem cells, immune cells, and keratinocytes. This observation suggests a complex interplay where various cell types may contribute to the release of exosomes and antimicrobial compounds at the interface between scales and viable tissue. These findings indicate that pangolin scales may serve as a multifaceted defense system, potentially contributing to innate immunity. Comparisons with human nail and hair revealed pangolin-specific proteins that were enriched in functions relating to sensing, immune responses, neutrophil degranulation, and stress responses. We demonstrated the antimicrobial activity of key pangolin scale components on pathogenic bacteria by antimicrobial assays.ConclusionsThis study identifies a potential role of pangolin scales and implicates scales, as possible determinants of pathogen defense due to their structure and contents. We indicate for the first time the presence of exosomes in pangolin scales and propose the new functions of scales and their mechanisms. This new mechanism could have implications for multiple fields, including providing interesting new research directions and important insights that can be useful for synthesizing and implementing new biomimetic antimicrobial approaches.

Transcriptomic Analysis of Genes Associated with Stinger Development at Different Life Stages of Apis mellifera.

Stingers, evolved from ovipositors, are an important defense organ for the Apidae, Vespidae, and Formicidae species. However, the molecular mechanism of stinger development remains unclear. Here, we show that the earliest time point for the appearance of stingers in Apis mellifera is at the 1-day-old worker pupal stage based on morphological observations and anatomy from the pre-pupal to adult stages. To discover the genes related to stinger development, we first comprehensively compared the stinger transcriptome at different stages and screened 1282, 186, and 166 highly expressed genes in the stingers of 1- and 5-day-old worker pupae and newly emerged worker bees (NEBs), respectively, then identified 25 DEGs involved in the early stage of stinger development. We found that Dll was a key candidate gene in the early development of A. mellifera stingers by combining analyses of the protein-protein interaction network and spatiotemporal expression patterns. An RNAi experiment showed that about 20% of individuals exhibited tip bending in the piercing parts of their stingers in the Dll-dsRNA-treated group, with the morphology presenting as side-side or front-back tip bending. This indicates that Dll plays a vital role in the early development of A. mellifera stingers. Together, our study provides insight into the molecular mechanism of Hymenoptera stinger development and an inspiration for the molecular breeding of gentle honeybee species with stinger abnormalities.

Varicella-zoster virus recapitulates its immune evasive behaviour in matured hiPSC-derived neurospheroids.

Varicella-zoster virus (VZV) encephalitis and meningitis are potential central nervous system (CNS) complications following primary VZV infection or reactivation. With Type-I interferon (IFN) signalling being an important first line cellular defence mechanism against VZV infection by the peripheral tissues, we here investigated the triggering of innate immune responses in a human neural-like environment. For this, we established and characterised 5-month matured hiPSC-derived neurospheroids (NSPHs) containing neurons and astrocytes. Subsequently, NSPHs were infected with reporter strains of VZV (VZVeGFP-ORF23) or Sendai virus (SeVeGFP), with the latter serving as an immune-activating positive control. Live cell and immunocytochemical analyses demonstrated VZVeGFP-ORF23 infection throughout the NSPHs, while SeVeGFP infection was limited to the outer NSPH border. Next, NanoString digital transcriptomics revealed that SeVeGFP-infected NSPHs activated a clear Type-I IFN response, while this was not the case in VZVeGFP-ORF23-infected NSPHs. Moreover, the latter displayed a strong suppression of genes related to IFN signalling and antigen presentation, as further demonstrated by suppression of IL-6 and CXCL10 production, failure to upregulate Type-I IFN activated anti-viral proteins (Mx1, IFIT2 and ISG15), as well as reduced expression of CD74, a key-protein in the MHC class II antigen presentation pathway. Finally, even though VZVeGFP-ORF23-infection seems to be immunologically ignored in NSPHs, its presence does result in the formation of stress granules upon long-term infection, as well as disruption of cellular integrity within the infected NSPHs. Concluding, in this study we demonstrate that 5-month matured hiPSC-derived NSPHs display functional innate immune reactivity towards SeV infection, and have the capacity to recapitulate the strong immune evasive behaviour towards VZV.

Diagnostic sensitivity and specificity of indicators of glutathione antioxidant system in spermatozoa of infertile men with different forms of pathospermia

Background. One of the most important antioxidant defence mechanism in spermatozoa is the gluthatione system which includes glutathione peroxidase (GPx), glutathione reductase (GR), glutathione S-transferase (GST) and reduced glutathione (GSH). It is promising to use ROC analysis, which allows to assessing the diagnostic sensitivity and specificity of indicators. Materials and methods. Infertile men were divided into 3 groups: patients with oligozoospermia (n = 30), asthenozoospermia (n = 34), and oligoasthenozoospermia (n = 22). To assess the diagnostic sensitivity and specificity of indicators, the values of the biomarkers were tested using the receiver operating characteristic (ROC) curve, and the area under it (AUC), the standard error (SE) and the 95% confidence interval (CI 95%) were calculated. Results. The ROC analysis showed that GP activity was characterized by excellent diagnostic significance for diagnosing both oligozoospermia and asthenozoospermia (the sensitivity was 100%, and specificity – 100%). The GR activity has moderate diagnostic significance, since the AUC is 0.654 (95% CI from 0.503 to 0.785, P = 0.0645) for oligozoospermic, the AUC is 0.612 (95% CI from 0.454 to 0.7555, P = 0.1979) for asthenozoospermic men. The analysis of the ROC curve revealed a good diagnostic value of GsT activity in sperm samples for the diagnosis of pathospermia (sensitivity of 75% and specificity of 80%). Simultaneously, it was shown that GSH content could not serve as valuable biomarkers for distinguishing patients with pathospermia from healthy controls, with an AUC of 0.615, corresponding to moderate diagnostic significance for oligozoospermia. Conclusion. The results of this study show that the cut-off points for the biomar­kers glutathione peroxidase and glutathione-S-transferase can be used to distinguish between patients with pathospermia and normozoospermia, and the parameters themselves can serve as valuable diagnostic biomarkers to distinguish patients with pathospermia from healthy controls, regardless of the causes of pathospermia. The value of these indicators below the cut-off point indicates the probable presence of pathology. Indicators of GR activity and GSH content have a low diagnostic value, which makes them unsuitable for use as laboratory tests for the diagnosis of male infertility.

Identifying a Gene Deficiency in the Antiviral Innate Immune Signaling Pathway.

Innate immunity is an important defense barrier for the human body. After viral pathogen-associated molecular patterns (PAMPs) are detected by host-pathogen recognition receptors (PRRs), the associated signaling pathways trigger the activation of the interferon (IFN) regulatory factor (IRF) family members and the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB). However, any gene defects among the signaling adaptors will compromise innate immune efficiency. Therefore, investigating genetic defects in the antiviral innate immune signaling pathway is important. We summarize the commonly used research methods related to antiviral immune gene defects and outline the relevant research protocols, which will help investigators study antiviral innate immunity.

Fas/FasL-Mediated Apoptosis and Inflammation Contribute to Recovery from HSV-2-Mediated Spinal Cord Infection.

Herpes simplex virus type 2 (HSV-2) is a sexually transmitted pathogen that causes a persistent infection in sensory ganglia. The infection manifests itself as genital herpes but in rare cases it can cause meningitis. In this study, we used a murine model of HSV-2 meningitis to show that Fas and FasL are induced within the CNS upon HSV-2 infection, both on resident microglia and astrocytes and on infiltrating monocytes and lymphocytes. Mice lacking Fas or FasL had a more severe disease development with significantly higher morbidity, mortality, and an overall higher CNS viral load. In parallel, these Fas/FasL-deficient mice showed a severely impaired infection-induced CNS inflammatory response with lower levels of infiltrating CD4+ T-cells, lower levels of Th1 cytokines and chemokines, and a shift in the balance between M1 and M2 microglia/monocytes. In vitro, we confirmed that Fas and FasL is required for the induction of leucocyte apoptosis, but also show that the Fas/FasL pathway is required for adequate cytokine and chemokine production by glial cells. In summary, our data show that the Fas/FasL cell death receptor pathway is an important defense mechanism in the spinal cord as it down-regulates HSV-2-induced inflammation while at the same time promoting adequate anti-viral immune responses against infection.

Manipulation of host phagocytosis by fungal pathogens and therapeutic opportunities.

An important host defence mechanism against pathogens is intracellular killing, which is achieved through phagocytosis, a cellular process for engulfing and neutralizing extracellular particles. Phagocytosis results in the formation of matured phagolysosomes, which are specialized compartments that provide a hostile environment and are considered the end point of the degradative pathway. However, all fungal pathogens studied to date have developed strategies to manipulate phagosomal function directly and also indirectly by redirecting phagosomes from the degradative pathway to a non-degradative pathway with the expulsion and even transfer of pathogens between cells. Here, using the major human fungal pathogens Aspergillus fumigatus, Candida albicans, Cryptococcus neoformans and Histoplasma capsulatum as examples, we discuss the processes involved in host phagosome-fungal pathogen interactions, with a focus on fungal evasion strategies. We also discuss recent approaches to targeting intraphagosomal pathogens, including the redirection of phagosomes towards degradative pathways for fungal pathogen eradication.

First line of defence: Eucalyptus leaf waxes influence infection by an aggressive fungal leaf pathogen.

Leaf epicuticular waxes provide important anatomical and chemical defences against fungi that infect leaves. In this study we analysed the leaf wax composition of Eucalyptus grandis × Eucalyptus urophylla hybrids with contrasting susceptibilities to Teratosphaeria leaf blight (TLB) caused by Teratosphaeria destructans, one of the most important foliar diseases of Eucalyptus. The Eucalyptus cuticular wax was extracted from non-inoculated and inoculated genotypes with different levels of susceptibility to TLB and analysed by gas chromatography-mass spectrometry. The results showed that a triterpenoid, cycloartenol (CAS), was abundant in a resistant genotype and that hexanedioic acid content increased in the resistant genotypes in response to T. destructans infection. In contrast, palmitic acid was significantly more abundant in the inoculated highly susceptible genotype. In-vitro and in-planta T.destructans spore germination assays with pure compounds, showed that CAS and hexanedioic acid significantly inhibited spore germination. Application of these two compounds to the leaves of a susceptible host also significantly increased resistance to infection. In contrast, palmitic acid promoted spore germination and, when applied to the leaves of a resistant genotype, increased colonization by the pathogen. This is the first study providing insights into differences in the leaf wax composition of hosts with different levels of susceptibility to T. destructans. It also showed that leaf wax compounds can modulate spore germination and, ultimately, host resistance to infection.