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In the course of plant evolution from aquatic to terrestrial environments, land plants (embryophytes) acquired a diverse array of specialized metabolites, including phenylpropanoids, flavonoids and cuticle components, enabling adaptation to various environmental stresses. While embryophytes and their closest algal relatives share candidate enzymes responsible for producing some of these compounds, the complete genetic network for their biosynthesis emerged in embryophytes. In this review, we analysed genomic data from chlorophytes, charophytes and embryophytes to identify genes related to phenylpropanoid, flavonoid and cuticle biosynthesis. By integrating published research, transcriptomic data and metabolite studies, we provide a comprehensive overview on how these specialized metabolic pathways have contributed to plant defence responses to pathogens in non-vascular bryophytes and vascular plants throughout evolution. The evidence suggests that these biosynthetic pathways have provided land plants with a repertoire of conserved and lineage-specific compounds, which have shaped immunity against invading pathogens. The discovery of additional enzymes and metabolites involved in bryophyte responses to pathogen infection will provide evolutionary insights into these versatile pathways and their impact on environmental terrestrial challenges.This article is part of the theme issue 'The evolution of plant metabolism'.

Vaccines are one of the most important means to prevent and control the epidemic of infectious diseases. Commercial vaccines not only include corresponding antigens, but also need vaccine adjuvants. Immune adjuvants play an increasingly important role in the research, development and manufacture of vaccines. Adjuvants combined with antigens can improve the stability, safety and immune efficiency of vaccines. Some substances that can enhance the immune response have been found in nature(mainly plants) and used as adjuvants in vaccines to improve the immune effect of vaccines. These plant-derived immune adjuvants often have the advantages of low toxicity, high stability, low price, etc., providing more possibilities for vaccine development. We summarized and analyzed the advantages, application research, particulate delivery systems, existing problems and future research focus of botanical adjuvant. It is hoped to provide new ideas for the research and development of immune adjuvants in the future., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Secondary metabolites mediate a broad variety of interactions between bacteria and fungi. Testing two plant growth-promoting microorganisms, a rhizobacterium and an arbuscular mycorrhizal fungus, a new study reveals their chemical interaction and an enhanced systemic induction of plant immunity., Competing Interests: Declaration of interests The author declares no competing interests., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Plants are central to global food production, and the pursuit of sustainability aims to enhance or preserve food quality while safeguarding the environment. Due to their immobility, plants are unable to evade unfavourable climatic setups or interactions with other living creatures. Upon their interaction with insect herbivores, plants face biotic stress, which is a constant challenge for plants, causing molecular, physiological, and biochemical changes and reducing their productivity. To combat biotic stress caused by herbivores, plants have evolved intricate defence mechanisms through growth regulators such as auxins, cytokinins, gibberellins, salicylic acid (SA), jasmonic acid (JA), ethylene (ET), abscisic acid (ABA), strigolactones and brassinosteroids. The intricate network of specific proteins, metabolites and certain phytohormones orchestrates plant defensive reactions, leading to their skilful coordination in responding to insect attacks. Comprehending the defence mechanisms holds the key to mitigating significant crop and economic losses. This review entails a comprehensive analysis of the role of growth regulators in enhancing plant immunity against herbivory, highlighting the substantial efforts by the scientific community to manage and mitigate damages from biotic stress in plants, ultimately contributing to the advancement of sustainable agriculture., (© 2024 Scandinavian Plant Physiology Society.)

This review article delves into the intricate relationship between levan, a versatile polysaccharide, and its role in enhancing plant resistance against pathogens. By exploring the potential applications of levan in agriculture and biotechnology, such as crop protection, stress tolerance enhancement, and biotechnological innovations, significant advancements in sustainable agriculture are uncovered. Despite challenges in optimizing application methods and addressing regulatory hurdles, understanding the mechanisms of levan-mediated plant immunity offers promising avenues for future research. This review underscores the implications of utilizing levan to develop eco-friendly solutions, reduce reliance on chemical pesticides, and promote sustainable agricultural practices. Ultimately, by unraveling the pivotal role of levan in plant-pathogen interactions, this review sets the stage for transformative innovations in agriculture and highlights the path towards a more resilient and sustainable agricultural future., Competing Interests: Declaration of competing interest No conflict of interest., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Pathogen attacks can cause significant damage to plants, posing a threaten to global food production. Plants have developed exquisite methods to rapidly store a key defensive hormone jasmonate (JA), which stimulates their entire evolutionary adaptive response to pathogen attack. However, understanding how plants initiate JA biosynthesis in response to pathogen attacks has remained elusive. In this review, we discuss the newly discovered JAV1-JAZ8-WRKY51 (JJW) complex, which plays a crucial role in regulating JA production to deter insect attacks. The JJW complex inhibits JA production in plants, maintaining a low baseline level of JA that promotes optimal plant development. However, when plants are attacked by insects, a rapid influx of calcium stimulates the JAV1 calcium-dependent protein phosphate, leading to the breakdown of the JJW complex and the activation of JA production. This surge in JA levels, initiates plant defense mechanisms against the invading insects. These findings shed light on the intricate defense system that plants have evolved to combat diseases., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Within the continuous tug-of-war between plants and microbes, RNA silencing stands out as a key battleground. Pathogens, in their quest to colonize host plants, have evolved a diverse arsenal of silencing suppressors as a common strategy to undermine the host's RNA silencing-based defenses. When RNA silencing malfunctions in the host, genes that are usually targeted and silenced by microRNAs (miRNAs) become active and can contribute to the reprogramming of host cells, providing an additional defense mechanism. A growing body of evidence suggests that miRNAs may act as intracellular sensors to enable a rapid response to pathogen threats. Herein we review how plant miRNA targets play a crucial role in immune responses against different pathogens., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

14-3-3 proteins, ubiquitously present in eukaryotic cells, are regulatory proteins involved in a plethora of cellular processes. In plants, they have been studied in the context of metabolism, development, and stress responses. Recent studies have highlighted the pivotal role of 14-3-3 proteins in regulating plant immunity. The ability of 14-3-3 proteins to modulate immune responses is primarily attributed to their function as interaction hubs, mediating protein-protein interactions and thereby regulating the activity and overall function of their binding partners. Here, we shed light on how 14-3-3 proteins contribute to plant defense mechanisms, the implications of their interactions with components of plant immunity cascades, and the potential for leveraging this knowledge for crop improvement strategies., Competing Interests: Declaration of interests No interests are declared., (Copyright © 2024. Published by Elsevier Ltd.)

Reactive oxygen species (ROS) and reactive nitrogen species (RNS) are critical for plant development as well as for its stress response. They can function as signaling molecules to orchestrate a well-defined response of plants to biotic stress. These responses are further fine-tuned by phytohormones, such as salicylic acid, jasmonic acid, and ethylene, to modulate immune response. In the past decades, the intricacies of redox and phytohormonal signaling have been uncovered during plant-pathogen interactions. This review explores the dynamic interplay of these components, elucidating their roles in perceiving biotic threats and shaping the plant's defense strategy. Molecular regulators and sites of oxidative burst have been explored during pathogen perception. Further, the interplay between various components of redox and phytohormonal signaling has been explored during bacterial, fungal, viral, and nematode infections as well as during insect pest infestation. Understanding these interactions highlights gaps in the current knowledge and provides insights into engineering crop varieties with enhanced resistance to pathogens and pests. This review also highlights potential applications of manipulating regulators of redox signaling to bolster plant immunity and ensure global food security. Future research should explore regulators of these signaling pathways as potential target to develop biotic stress-tolerant crops. Further insights are also needed into roles of endophytes and host microbiome modulating host ROS and RNS pool for exploiting them as biocontrol agents imparting resistance against pathogens in plants., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Background: The NAC transcription factor family, which is recognized as one of the largest plant-specific transcription factor families, comprises numerous members that are widely distributed among various higher plant species and play crucial regulatory roles in plant immunity., Results: In this paper, we provided a detailed summary of the roles that NAC transcription factors play in plant immunity via plant hormone pathways and reactive oxygen species pathways. In addition, we conducted in-depth investigations into the interactions between NAC transcription factors and pathogen effectors to summarize the mechanism through which they regulate the expression of defense-related genes and ultimately affect plant disease resistance., Conclusions: This paper presented a comprehensive overview of the crucial roles that NAC transcription factors play in regulating plant disease resistance through their involvement in diverse signaling pathways, acting as either positive or negative regulators, and thus provided references for further research on NAC transcription factors., (© 2024. The Author(s).)

Plants produce diverse small molecules rapidly in response to localized pathogenic attack. Some of the molecules are able to migrate systemically as mobile signals, leading to the immune priming that protects the distal tissues against future infections by a broad-spectrum of invaders. Such form of defense is unique in plants and is known as systemic acquired resistance (SAR). There are many small molecules identified so far with important roles in the systemic immune signaling, some may have the potential to act as the mobile systemic signal in SAR establishment. Here, we summarize the recent advances in SAR research, with a focus on the role and mechanisms of different small molecules in systemic immune signaling., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Ivo Feussner reports financial support was provided by Deutsche Forschungs Gemeinschaft (DFG). Lei Tian reports financial support was provided by Alexander-von-Humboldt Foundation. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

In the evolutionary arm race between plants and viral pathogens, the plant hormone abscisic acid (ABA) has surfaced as a crucial player. This review accumulates substantial evidence that portrays ABA as a crucial regulatory hub, coordinating the complex network of plant antiviral immunity. It is capable of synchronizing resistance pathways, yet it can also be exploited as a susceptibility factor by viral effectors. ABA fortifies multi-layered defenses on one hand, by activating RNA silencing mechanisms that precisely degrade viral genomes, strengthening plasmodesmal gateways with callose barriers, and priming the transcriptional programs of resistance genes. On the other hand, ABA can augment susceptibility by counteracting other defense hormones, dampening oxidative bursts, and inhibiting antiviral defence proteins. Interestingly, a variety of viruses have independently evolved strategies to manipulate ABA signalling pathways. This fascinating paradigm of hormonal conflicts unveils ABA as an important regulatory handle that determines infection trajectories. Future studies should carefully explore the multifaceted impacts of ABA modulation on plant immunity and susceptibility to diverse pathogens before considering practical applications in viral resistance strategies., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Masson SAS. All rights reserved.)

Reactive oxygen species (ROS) is a collective term for highly reactive oxygen derivatives, including singlet oxygen, hydroxyl radicals, superoxide anions, and hydrogen peroxide. In plants, ROS are produced in apoplasts, chloroplasts, mitochondria, and peroxisomes. Although ROS are toxic when their levels exceed a certain threshold, low-concentration ROS can serve as essential signaling molecules for plant growth and development, as well as plant responses to abiotic and biotic stresses. Various aspects of the role of ROS in plants have been discussed in previous reviews. In this review, we first summarize recent progress in the regulatory mechanisms of apoplastic ROS signaling and then propose its potential roles in plant defense against vascular pathogens to provide new ideas for the prevention and control of vascular diseases., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

In order to discriminate between detrimental, commensal, and beneficial microbes, plants rely on polysaccharides such as β-glucans, which are integral components of microbial and plant cell walls. The conversion of cell wall-associated β-glucan polymers into a specific outcome that affects plant-microbe interactions is mediated by hydrolytic and non-hydrolytic β-glucan-binding proteins. These proteins play crucial roles during microbial colonization: they influence the composition and resilience of host and microbial cell walls, regulate the homeostasis of apoplastic concentrations of β-glucan oligomers, and mediate β-glucan perception and signaling. This review outlines the dual roles of β-glucans and their binding proteins in plant immunity and symbiosis, highlighting recent discoveries on the role of β-glucan-binding proteins as modulators of immunity and as symbiosis receptors involved in the fine-tuning of microbial accommodation., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this article., (Copyright © 2024 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

Beneficial microbes induce resistance in plants (MIR), imposing both lethal and sublethal effects on herbivorous insects. We argue that herbivores surviving MIR carry metabolic and immunological imprints of MIR with cascading effects across food webs. We propose that incorporating such cascading effects will strongly enhance the current MIR research framework., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Fungal effector proteins function at the interfaces of diverse interactions between fungi and their plant and animal hosts, facilitating interactions that are pathogenic or mutualistic. Recent advancements in protein structure prediction have significantly accelerated the identification and functional predictions of these rapidly evolving effector proteins. This development enables scientists to generate testable hypotheses for functional validation using experimental approaches. Research frontiers in effector biology include understanding pathways through which effector proteins are secreted or translocated into host cells, their roles in manipulating host microbiomes, and their contribution to interacting with host immunity. Comparative effector repertoires among different fungal-host interactions can highlight unique adaptations, providing insights for the development of novel antifungal therapies and biocontrol strategies., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Plants and insects have co-existed for almost 400 million years and their interactions can be beneficial or harmful, thus reflecting their intricate co-evolutionary dynamics. Many herbivorous arthropods cause tremendous crop loss, impacting the agro-economy worldwide. Plants possess an arsenal of chemical defenses that comprise diverse secondary metabolites that help protect against harmful herbivorous arthropods. In response, the strategies that herbivores use to cope with plant defenses can be behavioral, or molecular and/or biochemical of which salivary secretions are a key determinant. Insect salivary secretions/oral secretions (OSs) play a crucial role in plant immunity as they contain several biologically active elicitors and effector proteins that modulate plants' defense responses. Using this oral secretion cocktail, insects overcome plant natural defenses to allow successful feeding. However, a lack of knowledge of the nature of the signals present in oral secretion cocktails has resulted in reduced mechanistic knowledge of their cellular perception. In this review, we discuss the latest knowledge on herbivore oral secretion derived elicitors and effectors and various mechanisms involved in plant defense modulation. Identification of novel herbivore-released molecules and their plant targets should pave the way for understanding the intricate strategies employed by both herbivorous arthropods and plants in their interactions., (© The Author(s) 2024. Published by Oxford University Press on behalf of Japanese Society of Plant Physiologists. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site–for further information please contact journals.permissions@oup.com.)

Arbuscular mycorrhizal (AM) symbiosis is the oldest and most widespread mutualistic association on Earth and involves plants and soil fungi belonging to Glomeromycotina. A complex molecular, cellular, and genetic developmental program enables partner recognition, fungal accommodation in plant tissues, and activation of symbiotic functions such as transfer of phosphorus in exchange for carbohydrates and lipids. AM fungi, as ancient obligate biotrophs, have evolved strategies to circumvent plant defense responses to guarantee an intimate and long-lasting mutualism. They are among those root-associated microorganisms able to boost plants' ability to cope with biotic stresses leading to mycorrhiza-induced resistance (MIR), which can be effective across diverse hosts and against different attackers. Here, we examine the molecular mechanisms underlying the modulation of plant immunity during colonization by AM fungi and at the onset and display of MIR against belowground and aboveground pests and pathogens. Understanding the MIR efficiency spectrum and its regulation is of great importance to optimizing the biotechnological application of these beneficial microbes for sustainable crop protection.

Plant-environment interactions, particularly biotic stress, are increasingly essential for global food security due to crop losses in the dynamic environment. Therefore, understanding plant responses to biotic stress is vital to mitigate damage. Beneficial microorganisms and their association with plants can reduce the damage associated with plant pathogens. One such group is PGPR (Plant growth-promoting rhizobacteria), which influences plant immunity significantly by interacting with biotic stress factors and plant signalling compounds. This review explores the types, metabolism, and mechanisms of action of PGPR, including their enzyme pathways and the signalling compounds secreted by PGPR that modulate gene and protein expression during plant defence. Furthermore, the review will delve into the crosstalk between PGPR and other plant growth regulators and signalling compounds, elucidating the physiological, biochemical, and molecular insights into PGPR's impact on plants under multiple biotic stresses, including interactions with fungi, bacteria, and viruses. Overall, the review comprehensively adds to our knowledge about PGPR's role in plant immunity and its application for agricultural resilience and food security., (© 2024 Scandinavian Plant Physiology Society.)

Undifferentiated plant and animal stem cells are essential for cell, tissue, and organ differentiation, development, and growth. They possess unusual antiviral immunity which differs from that in specialized cells. By comparison to animal stem cells, we discuss how plant stem cells defend against viral invasion and beyond., Competing Interests: Declaration of interests The authors declare no conflicts of interests., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Bivalent histone modifications regulate gene expression during development, but little is known about their function in plant-microbe interactions. In a recent report, Zhao et al. showed that expression of bivalent chromatin-marked gene 1 (BCG1), containing a pathogen-associated molecular pattern (PAMP) motif, is epigenetically regulated by trimethylation of lysine 4 (H3K4me3) and lysine 27 (H3K27me3) of histone H3 to evade plant immunity., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Rising global temperatures pose a threat to plant immunity, making them more susceptible to diseases. The impact of temperature on plant immunity against biotrophic and hemi-biotrophic pathogens is well documented, while its effect on necrotrophs remains poorly understood. We venture into the uncharted territory of necrotrophic fungal pathogens in the face of rising temperatures. We discuss the role of the plant hormones salicylic acid (SA) and jasmonic acid (JA) in providing resistance to necrotrophs and delve into the temperature sensitivity of the SA pathway. Additionally, we explore the repercussions of increased temperatures on plant susceptibility to necrotrophs. We put forward a research agenda with an experimental framework aimed at providing a comprehensive understanding of how plants and pathogens adapt to increasing temperatures., (© 2024 The Author(s). New Phytologist © 2024 New Phytologist Foundation.)

Alternative splicing (AS) is an evolutionarily conserved cellular process in eukaryotes in which multiple messenger RNA (mRNA) transcripts are produced from a single gene. The concept that AS adds to transcriptome complexity and proteome diversity introduces a new perspective for understanding how phytopathogen-induced alterations in host AS cause diseases. Recently, it has been recognized that AS represents an integral component of the plant immune system during parasitic, commensalistic, and symbiotic interactions. Here, I provide an overview of recent progress detailing the reprogramming of plant AS by phytopathogens and the functional implications on disease phenotypes. Additionally, I discuss the vital function of AS of immune receptors in regulating plant immunity and how phytopathogens use effector proteins to target key components of the splicing machinery and exploit alternatively spliced variants of immune regulators to negate defense responses. Finally, the functional association between AS and nonsense-mediated mRNA decay in the context of plant-pathogen interface is recapitulated.

The reduction in crop yield caused by pathogens and pests presents a significant challenge to global food security. Genetic engineering, which aims to bolster plant defence mechanisms, emerges as a cost-effective solution for disease control. However, this approach often incurs a growth penalty, known as the growth-defence trade-off. The precise molecular mechanisms governing this phenomenon are still not completely understood, but they generally fall under two main hypotheses: a "passive" redistribution of metabolic resources, or an "active" regulatory choice to optimize plant fitness. Despite the knowledge gaps, considerable practical endeavours are in the process of disentangling growth from defence. The plant microbiome, encompassing both above- and below-ground components, plays a pivotal role in fostering plant growth and resilience to stresses. There is increasing evidence which indicates that plants maintain intimate associations with diverse, specifically selected microbial communities. Meta-analyses have unveiled well-coordinated, two-way communications between plant shoots and roots, showcasing the capacity of plants to actively manage their microbiota for balancing growth with immunity, especially in response to pathogen incursions. This review centers on successes in making use of specific root-associated microbes to mitigate the growth-defence trade-off, emphasizing pivotal advancements in unravelling the mechanisms behind plant growth and defence. These findings illuminate promising avenues for future research and practical applications., (© 2024 The Authors. Plant Biotechnology Journal published by Society for Experimental Biology and The Association of Applied Biologists and John Wiley & Sons Ltd.)

The growth-promoting and immune modulatory properties of different strains of plant growth promoting rhizobacteria (PGPR) fluorescent Pseudomonads complex (PFPC) can be explored to combat food security challenges. These PFPC prime plants through induced systemic resistance, fortify plants to overcome future pathogen-mediated vulnerability by eliciting robust systemic acquired resistance through regulation by nonexpressor of pathogenesis-related genes 1. Moreover, outer membrane vesicles released from Pseudomonas fluorescens also elicit a broad spectrum of immune responses, presenting a rapid viable alternative to whole cells. Thus, PFPC can help the host to maintain an equilibrium between growth and immunity, ultimately leads to increased crop yield., Competing Interests: Declaration of competing interest I, as the corresponding author, declare on behalf of all the authors of the paper that no financial conflict of interest exists in relation to the work described., (Copyright © 2024 Institut Pasteur. Published by Elsevier Masson SAS. All rights reserved.)

Mycorrhizal fungi, a category of fungi that form symbiotic relationships with plant roots, can participate in the induction of plant disease resistance by secreting phosphatase enzymes. While extensive research exists on the mechanisms by which mycorrhizal fungi induce resistance, the specific contributions of phosphatases to these processes require further elucidation. This article reviews the spectrum of mycorrhizal fungi-induced resistance mechanisms and synthesizes a current understanding of how phosphatases mediate these effects, such as the induction of defense structures in plants, the negative regulation of plant immune responses, and the limitation of pathogen invasion and spread. It explores the role of phosphatases in the resistance induced by mycorrhizal fungi and provides prospective future research directions in this field.

Prokaryotes have evolved a multitude of defense systems to protect against phage predation. Some of these resemble eukaryotic genes involved in antiviral responses. Here, we set out to systematically project the current knowledge of eukaryotic-like antiviral defense systems onto prokaryotic genomes, using Pseudomonas aeruginosa as a model organism. Searching for phage defense systems related to innate antiviral genes from vertebrates and plants, we uncovered over 450 candidates. We validated six of these phage defense systems, including factors preventing viral attachment, R-loop-acting enzymes, the inflammasome, ubiquitin pathway, and pathogen recognition signaling. Collectively, these defense systems support the concept of deep evolutionary links and shared antiviral mechanisms between prokaryotes and eukaryotes., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2024 Elsevier Inc. All rights reserved.)

The apoplast is one of the first cellular compartments outside the plasma membrane encountered by phytopathogenic microbes in the early stages of plant tissue invasion. Plants have developed sophisticated surveillance mechanisms to sense danger events at the cell surface and promptly activate immunity. However, a fine tuning of the activation of immune pathways is necessary to mount a robust and effective defense response. Several endogenous proteins and enzymes are synthesized as inactive precursors, and their post-translational processing has emerged as a critical mechanism for triggering alarms in the apoplast. In this review, we focus on the precursors of phytocytokines, cell wall remodeling enzymes, and proteases. The physiological events that convert inactive precursors into immunomodulatory active peptides or enzymes are described. This review also explores the functional synergies among phytocytokines, cell wall damage-associated molecular patterns, and remodeling, highlighting their roles in boosting extracellular immunity and reinforcing defenses against pests., (Copyright © 2024 The Author(s). Published by Elsevier Inc. All rights reserved.)

Plants continuously monitor the environment to detect changing conditions and to properly respond, avoiding deleterious effects on their fitness and survival. An enormous number of cell surface and intracellular immune receptors are deployed to perceive danger signals associated with microbial infections. Ligand binding by cognate receptors represents the first essential event in triggering plant immunity and determining the outcome of the tissue invasion attempt. Reactive oxygen and nitrogen species (ROS/RNS) are secondary messengers rapidly produced in different subcellular localizations upon the perception of immunogenic signals. Danger signal transduction inside the plant cells involves cytoskeletal rearrangements as well as several organelles and interactions between them to activate key immune signaling modules. Such immune processes depend on ROS and RNS accumulation, highlighting their role as key regulators in the execution of the immune cellular program. In fact, ROS and RNS are synergic and interdependent intracellular signals required for decoding danger signals and for the modulation of defense-related responses. Here we summarize current knowledge on ROS/RNS production, compartmentalization, and signaling in plant cells that have perceived immunogenic danger signals., (© The Author(s) 2023. Published by Oxford University Press on behalf of the Society for Experimental Biology. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.)

Plants fully depend on their immune systems to defend against pathogens. Upon pathogen attack, plants not only activate immune responses at the infection site but also trigger a defense mechanism known as systemic acquired resistance (SAR) in distal systemic tissues to prevent subsequent infections by a broad-spectrum of pathogens. SAR is induced by mobile signals produced at the infection site. Accumulating evidence suggests that reactive oxygen species (ROS) play a central role in SAR signaling. ROS burst at the infection site is one of the earliest cellular responses following pathogen infection and can spread to systemic tissues through membrane-associated NADPH oxidase-dependent relay production of ROS. It is well known that ROS ignite redox signaling and, when in excess, cause oxidative stress, damaging cellular components. In this review, we summarize current knowledge on redox regulation of several SAR signaling components. We discuss the ROS amplification loop in systemic tissues involving multiple SAR mobile signals. Moreover, we highlight the essential role of oxidative stress in generating SAR signals including azelaic acid and extracellular NAD(P) [eNAD(P)]. Finally, we propose that eNAD(P) is a damage-associated molecular pattern serving as a converging point of SAR mobile signals in systemic tissues., (© The Author(s) 2024. Published by Oxford University Press on behalf of the Society for Experimental Biology. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.)

The role of the plant innate immune system in the defense and symbiosis processes becomes integral in a complex network of interactions between plants and fungi. An understanding of the molecular characterization of the plant innate immune system is crucial because it constitutes plants' self-defense shield against harmful fungi, while creating mutualistic relationships with beneficial fungi. Due to the plant-induced awareness and their complexity of interaction with fungi, sufficient assessment of the participation of the plant innate immune system in ecological balance, agriculture, and maintenance of an infinite ecosystem is mandatory. Given the current global challenge, such as the surge of plant-infectious diseases, and pursuit of sustainable forms of agriculture; it is imperative to understand the molecular language of communication between plants and fungi. That knowledge can be practically used in diverse areas, e.g., in agriculture, new tactics may be sought after to try new methods that boost crop receptiveness against fungal pathogens and reduce the dependence on chemical management. Also, it could boost sustainable agricultural practices via enhancing mycorrhizal interactions that promote nutrient absorption and optimum cropping with limited exposure of environmental contamination. Moreover, this review offers insights that go beyond agriculture and can be manipulated to boost plant conservation, environmental restoration, and quality understanding of host-pathogen interactions. Consequently, this specific review paper has offered a comprehensive view of the complex plant innate immune-based responses with fungi and the mechanisms in which they interact., (Copyright © 2024 Elsevier GmbH. All rights reserved.)

Nanotechnology has emerged as a promising field with the potential to revolutionize agriculture, particularly in enhancing plant defense mechanisms. Nanoparticles (NPs) are instrumental in plant defense priming, where plants are pre-exposed to controlled levels of stress to heighten their alertness and responsiveness to subsequent stressors. This process improves overall plant performance by enabling quicker and more effective responses to secondary stimuli. This review explores the application of NPs as priming agents, utilizing their unique physicochemical properties to bolster plants' innate defense mechanisms. It discusses key findings in NP-based plant defense priming, including various NP types such as metallic, metal oxide, and carbon-based NPs. The review also investigates the intricate mechanisms by which NPs interact with plants, including uptake, translocation, and their effects on plant physiology, morphology, and molecular processes. Additionally, the review examines how NPs can enhance plant responses to a range of stressors, from pathogen attacks and herbivore infestations to environmental stresses. It also discusses NPs' ability to improve plants' tolerance to abiotic stresses like drought, salinity, and heavy metals. Safety and regulatory aspects of NP use in agriculture are thoroughly addressed, emphasizing responsible and ethical deployment for environmental and human health safety. By harnessing the potential of NPs, this approach shows promise in reducing crop losses, increasing yields, and enhancing global food security while minimizing the environmental impact of traditional agricultural practices. The review concludes by emphasizing the importance of ongoing research to optimize NP formulations, dosages, and delivery methods for practical application in diverse agricultural settings., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Masson SAS. All rights reserved.)

Plants face a relentless onslaught from a diverse array of pathogens in their natural environment, to which they have evolved a myriad of strategies that unfold across various temporal scales. Cell surface pattern recognition receptors (PRRs) detect conserved elicitors from pathogens or endogenous molecules released during pathogen invasion, initiating the first line of defence in plants, known as pattern-triggered immunity (PTI), which imparts a baseline level of disease resistance. Inside host cells, pathogen effectors are sensed by the nucleotide-binding/leucine-rich repeat (NLR) receptors, which then activate the second line of defence: effector-triggered immunity (ETI), offering a more potent and enduring defence mechanism. Moreover, PTI and ETI collaborate synergistically to bolster disease resistance and collectively trigger a cascade of downstream defence responses. This article provides a comprehensive review of plant defence responses, offering an overview of the stepwise activation of plant immunity and the interactions between PTI-ETI synergistic signal transduction., (© 2024 The Authors. Plant Biotechnology Journal published by Society for Experimental Biology and The Association of Applied Biologists and John Wiley & Sons Ltd.)

In recent years, the field of plant immunity has witnessed remarkable breakthroughs. During the co-evolution between plants and pathogens, plants have developed a wealth of intricate defense mechanisms to safeguard their survival. Newly identified immune receptors have added unexpected complexity to the surface and intracellular sensor networks, enriching our understanding of the ongoing plant-pathogen interplay. Deciphering the molecular mechanisms of resistosome shapes our understanding of these mysterious molecules in plant immunity. Moreover, technological innovations are expanding the horizon of the plant-pathogen battlefield into spatial and temporal scales. While the development provides new opportunities for untangling the complex realm of plant immunity, challenges remain in uncovering plant immunity across spatiotemporal dimensions from both molecular and cellular levels., Competing Interests: Conflict of interest The authors declare no conflict of interest., (Copyright © 2024 Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, and Genetics Society of China. Published by Elsevier Ltd. All rights reserved.)

This review explores the role of pectin, a complex polysaccharide found in the plant cell wall, in mediating immune responses during interactions between plants and microbes. The objectives of this study were to investigate the molecular mechanisms underlying pectin-mediated immune responses and to understand how these interactions shape plant-microbe communication. Pectin acts as a signaling molecule, triggering immune responses such as the production of antimicrobial compounds, reinforcement of the cell wall, and activation of defense-related genes. Pectin functions as a target for pathogen-derived enzymes, enabling successful colonization by certain microbial species. The document discusses the complexity of pectin-based immune signaling networks and their modulation by various factors, including pathogen effectors and host proteins. It also emphasizes the importance of understanding the crosstalk between pectin-mediated immunity and other defense pathways to develop strategies for enhancing plant resistance against diseases. The insights gained from this study have implications for the development of innovative approaches to enhance crop protection and disease management in agriculture. Further investigations into the components and mechanisms involved in pectin-mediated immunity will pave the way for future advancements in plant-microbe interaction research., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Plants can experience a variety of environmental stresses that significantly impact their fitness and survival. Additionally, biotic stress can harm agriculture, leading to reduced crop yields and economic losses worldwide. As a result, plants have developed defense strategies to combat potential invaders. These strategies involve regulating redox homeostasis. Several studies have documented the positive role of plant antioxidants, including Ascorbate (Asc), under biotic stress conditions. Asc is a multifaceted antioxidant that scavenges ROS, acts as a co-factor for different enzymes, regulates gene expression, and facilitates iron transport. However, little attention has been given to Asc and its transport, regulatory effects, interplay with phytohormones, and involvement in defense processes under biotic stress. Asc interacts with other components of the redox system and phytohormones to activate various defense responses that reduce the growth of plant pathogens and promote plant growth and development under biotic stress conditions. Scientific reports indicate that Asc can significantly contribute to plant resistance against biotic stress through mutual interactions with components of the redox and hormonal systems. This review focuses on the role of Asc in enhancing plant resistance against pathogens. Further research is necessary to gain a more comprehensive understanding of the molecular and cellular regulatory processes involved., (© 2024 The Author(s). Physiologia Plantarum published by John Wiley & Sons Ltd on behalf of Scandinavian Plant Physiology Society.)

Pathogenic viruses are a constant threat to all organisms, including plants. However, in plants, a small group of cells (stem cells) protect themselves from viral invasion. Recently, Incarbone et al. uncovered a novel salicylic acid (SA) and RNAi mechanism of stem cell resistance, broadening our understanding of RNAi-mediated antiviral plant immunity., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Viruses, causal agents of devastating diseases in plants, are obligate intracellular pathogens composed of a nucleic acid genome and a limited number of viral proteins. The diversity of plant viruses, their diminutive molecular nature, and their symplastic localization pose challenges to understanding the interplay between these pathogens and their hosts in the currently accepted framework of plant innate immunity. It is clear, nevertheless, that plants can recognize the presence of a virus and activate antiviral immune responses, although our knowledge of the breadth of invasion signals and the underpinning sensing events is far from complete. Below, I discuss some of the demonstrated or hypothesized mechanisms enabling viral recognition in plants, the step preceding the onset of antiviral immunity, as well as the strategies viruses have evolved to evade or suppress their detection.

Plant lipids are essential cell constituents with many structural, storage, signaling, and defensive functions. During plant-pathogen interactions, lipids play parts in both the preexisting passive defense mechanisms and the pathogen-induced immune responses at the local and systemic levels. They interact with various components of the plant immune network and can modulate plant defense both positively and negatively. Under biotic stress, lipid signaling is mostly associated with oxygenated natural products derived from unsaturated fatty acids, known as oxylipins; among these, jasmonic acid has been of great interest as a specific mediator of plant defense against necrotrophic pathogens. Although numerous studies have documented the contribution of oxylipins and other lipid-derived species in plant immunity, their specific roles in plant-pathogen interactions and their involvement in the signaling network require further elucidation. This review presents the most relevant and recent studies on lipids and lipid-derived signaling molecules involved in plant-pathogen interactions, with the aim of providing a deeper insight into the mechanisms underpinning lipid-mediated regulation of the plant immune system.

Protein homeostasis, namely the balance between protein synthesis and degradation, must be finely controlled to ensure cell survival, notably through the ubiquitin-proteasome system (UPS). In all species, including plants, homeostasis is disrupted by biotic and abiotic stresses. A key player in the maintenance of protein balance, the protein CDC48, shows emerging functions in plants, particularly in response to biotic stress. In this review on CDC48 in plants, we detail its highly conserved structure, describe a gene expansion that is only present in Viridiplantae, discuss its various functions and regulations, and finally highlight its recruitment, still not clear, during the plant immune response., Competing Interests: Declaration of interests The authors declare no competing interests, (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Filamentous pathogens that cause plant diseases such as powdery mildew, rust, anthracnose, and late blight continue to represent an enormous challenge for farmers worldwide. Interestingly, these pathogens, although phylogenetically distant, initiate pathogenesis in a very similar way by penetrating the cell wall and establishing a feeding structure inside the plant host cell. To prevent pathogen ingress, the host cell responds by forming defence structures known as papillae and encasements that are thought to mediate pre- and post-invasive immunity, respectively. This form of defence is evolutionarily conserved in land plants and is highly effective and durable against a broad selection of non-adapted filamentous pathogens. As most pathogens have evolved strategies to overcome the defences of only a limited range of host plants, the papilla/encasement response could hold the potential to become an optimal transfer of resistance from one plant species to another. In this review I lay out current knowledge of the involvement of membrane trafficking that forms these important defence structures and highlight some of the questions that still need to be resolved., (© The Author(s) 2024. Published by Oxford University Press on behalf of the Society for Experimental Biology. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.)

The eukaryotic cytoskeleton is a complex scaffold consisting of actin filaments, intermediate filaments, and microtubules. Although fungi and plants lack intermediate filaments, their dynamic structural network of actin filaments and microtubules regulates cell shape, division, polarity, and vesicular trafficking. However, the specialized functions of the cytoskeleton during plant-fungus interactions remain elusive. Recent reports demonstrate that the plant cytoskeleton responds to signal cues and pathogen invasion through remodeling, thereby coordinating immune receptor trafficking, membrane microdomain formation, aggregation of organelles, and transport of defense compounds. Emerging evidence also suggests that cytoskeleton remodeling further regulates host immunity by triggering salicylic acid signaling, reactive oxygen species generation, and pathogenesis-related gene expression. During host invasion, fungi undergo systematic cytoskeleton remodeling, which is crucial for successful host penetration and colonization. Furthermore, phytohormones act as an essential regulator of plant cytoskeleton dynamics and are frequently targeted by fungal effectors to disrupt the host's growth-defense balance. This review discusses recent advances in the understanding of cytoskeleton dynamics during plant-fungus interactions and provides novel insights into the relationship between phytohormones and cytoskeleton remodeling upon pathogen attack. We also highlight the importance of fungal cytoskeleton rearrangements during host colonization and suggest directions for future investigations in this field., (© The Author(s) 2024. Published by Oxford University Press on behalf of the Society for Experimental Biology. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.)

Phytopathogens cause plant diseases that threaten food security. Unlike mammals, plants lack an adaptive immune system and rely on their innate immune system to recognize and respond to pathogens. Plant response to a pathogen attack requires precise coordination of intracellular traffic and signaling. Spatial and/or temporal defects in coordinating signals and cargo can lead to detrimental effects on cell development. The role of intracellular traffic comes into a critical focus when the cell sustains biotic stress. In this review, we discuss the current understanding of the post-immune activation logistics of plant defense. Specifically, we focus on packaging and shipping of defense-related cargo, rerouting of intracellular traffic, the players enabling defense-related traffic, and pathogen-mediated subversion of these pathways. We highlight the roles of the cytoskeleton, cytoskeleton-organelle bridging proteins, and secretory vesicles in maintaining pathways of exocytic defense, acting as sentinels during pathogen attack, and the necessary elements for building the cell wall as a barrier to pathogens. We also identify points of convergence between mammalian and plant trafficking pathways during defense and highlight plant unique responses to illustrate evolutionary adaptations that plants have undergone to resist biotic stress., (© 2024 Bhandari and Brandizzi.)

The plant extracellular space, referred to as the apoplast, is inhabited by a variety of microorganisms. Reflecting the crucial nature of this compartment, both plants and microorganisms seek to control, exploit and respond to its composition. Upon sensing the apoplastic environment, pathogens activate virulence programmes, including the delivery of effectors with well-established roles in suppressing plant immunity. We posit that another key and foundational role of effectors is niche establishment - specifically, the manipulation of plant physiological processes to enrich the apoplast in water and nutritive metabolites. Facets of plant immunity counteract niche establishment by restricting water, nutrients and signals for virulence activation. The complex competition to control and, in the case of pathogens, exploit the apoplast provides remarkable insights into the nature of virulence, host susceptibility, host defence and, ultimately, the origin of phytopathogenesis. This novel framework focuses on the ecology of a microbial niche and highlights areas of future research on plant-microorganism interactions., (© 2024. Springer Nature Limited.)

In nature, plants are constantly colonized by a massive diversity of microbes engaged in mutualistic, pathogenic or commensal relationships with the host. Molecular patterns present in these microbes activate pattern-triggered immunity (PTI), which detects microbes in the apoplast or at the tissue surface. Whether and how PTI distinguishes among soil-borne pathogens, opportunistic pathogens, and commensal microbes within the soil microbiota remains unclear. PTI is a multimodal series of molecular events initiated by pattern perception, such as Ca2+ influx, reactive oxygen burst, and extensive transcriptional and metabolic reprogramming. These short-term responses may manifest within minutes to hours, while the long-term consequences of chronic PTI activation persist for days to weeks. Chronic activation of PTI is detrimental to plant growth, so plants need to coordinate growth and defense depending on the surrounding biotic and abiotic environments. Recent studies have demonstrated that root-associated commensal microbes can activate or suppress immune responses to variable extents, clearly pointing to the role of PTI in root-microbiota interactions. However, the molecular mechanisms by which root commensals interfere with root immunity and root immunity modulates microbial behavior remain largely elusive. Here, with a focus on the difference between short-term and long-term PTI responses, we summarize what is known about microbial interference with host PTI, especially in the context of root microbiota. We emphasize some missing pieces that remain to be characterized to promote the ultimate understanding of the role of plant immunity in root-microbiota interactions., (© The Author(s) 2024. Published by Oxford University Press on behalf of Japanese Society of Plant Physiologists. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site–for further information please contact journals.permissions@oup.com.)

In nature, plants defend themselves against pathogen attack by activating an arsenal of defense mechanisms. During the last decades, work mainly focused on the understanding of qualitative disease resistance mediated by a few genes conferring an almost complete resistance, while quantitative disease resistance (QDR) remains poorly understood despite the fact that it represents the predominant and more durable form of resistance in natural populations and crops. Here, we review our past and present work on the dissection of the complex mechanisms underlying QDR in Arabidopsis thaliana. The strategies, main steps and challenges of our studies related to one atypical QDR gene, RKS1 (Resistance related KinaSe 1), are presented. First, from genetic analyses by QTL (Quantitative Trait Locus) mapping and GWAs (Genome Wide Association studies), the identification, cloning and functional analysis of this gene have been used as a starting point for the exploration of the multiple and coordinated pathways acting together to mount the QDR response dependent on RKS1. Identification of RKS1 protein interactors and complexes was a first step, systems biology and reconstruction of protein networks were then used to decipher the molecular roadmap to the immune responses controlled by RKS1. Finally, exploration of the potential impact of key components of the RKS1-dependent gene network on leaf microbiota offers interesting and challenging perspectives to decipher how the plant immune systems interact with the microbial communities' systems.

Plant diseases caused by pathogens pose significant threats to agricultural productivity and food security worldwide. The traditional approach of relying on chemical pesticides for disease management has proven to be unsustainable, emphasizing the urgent need for sustainable and environmentally friendly alternatives. One promising strategy is to enhance plant resistance against pathogens through various methods. This review aims to unveil and explore effective methods for stimulating plant resistance, transforming vulnerable plants into vigilant defenders against pathogens. We discuss both conventional and innovative approaches, including genetic engineering, induced systemic resistance (ISR), priming, and the use of natural compounds. Furthermore, we analyze the underlying mechanisms involved in these methods, highlighting their potential advantages and limitations. Through an understanding of these methods, scientists and agronomists can develop novel strategies to combat plant diseases effectively while minimizing the environmental impact. Ultimately, this research offers valuable insights into harnessing the plant's innate defense mechanisms and paves the way for sustainable disease management practices in agriculture., Competing Interests: The authors declare no conflict of interest., (© 2024 The Author(s). Published by IMR Press.)