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Citrus yellow vein-clearing virus (Potexvirus citriflavivenae; CYVCV) is an increasing threat to citrus cultivation. Notably, the role of zinc finger proteins (ZFPs) in mediating viral resistance in citrus plants is unclear. In this study, we demonstrated that ZFPs ClSUP and ClDOF3.4 enhanced citrus defense responses against CYVCV in Eureka lemon (Citrus limon 'Eureka'). ClSUP interacted with the coat protein (CP) of CYVCV to reduce CP accumulation and inhibited its silencing suppressor function. Overexpression of CISUP triggered reactive oxygen species (ROS) and salicylic acid (SA) pathways, and enhanced resistance to CYVCV infection. In contrast, ClSUP silencing resulted in increased CP accumulation and down-regulated ROS and SA-related genes. ClDOF3.4 interacted with ClSUP to facilitate its interactions with CP. Furthermore, ClDOF3.4 synergistically regulated the accumulation of ROS and SA with ClSUP and accelerated down-regulation of CP accumulation. Transgenic plants co-expressing ClSUP and ClDOF3.4 significantly decreased the CYVCV. These findings provide a new reference for understanding the interaction mechanism between the host and CYVCV. [ABSTRACT FROM AUTHOR]

Xylanases derived from fungi, including phytopathogenic and nonpathogenic fungi, are commonly known to trigger plant immune responses. However, there is limited research on the ability of bacterial‐derived xylanases to trigger plant immunity. Here, a novel xylanase named CcXyn was identified from the myxobacterium Cystobacter sp. 0969, which displays broad‐spectrum activity against both phytopathogenic fungi and bacteria. CcXyn belongs to the glycoside hydrolases (GH) 11 family and shares a sequence identity of approximately 32.0%–45.0% with fungal xylanases known to trigger plant immune responses. Treatment of Nicotiana benthamiana with purified CcXyn resulted in the induction of hypersensitive response (HR) and defence responses, such as the production of reactive oxygen species (ROS) and upregulation of defence gene expression, ultimately enhancing the resistance of N. benthamiana to Phytophthora nicotianae. These findings indicated that CcXyn functions as a microbe‐associated molecular pattern (MAMP) elicitor for plant immune responses, independent of its enzymatic activity. Similar to fungal xylanases, CcXyn was recognized by the NbRXEGL1 receptor on the cell membrane of N. benthamiana. Downstream signalling was shown to be independent of the BAK1 and SOBIR1 co‐receptors, indicating the involvement of other co‐receptors in signal transduction following CcXyn recognition in N. benthamiana. Moreover, xylanases from other myxobacteria also demonstrated the capacity to trigger plant immune responses in N. benthamiana, indicating that xylanases in myxobacteria are ubiquitous in triggering plant immune functions. This study expands the understanding of xylanases with plant immune response‐inducing properties and provides a theoretical basis for potential applications of myxobacteria in biocontrol strategies against phytopathogens. [ABSTRACT FROM AUTHOR]

Abstract Background Rye (Secale cereale L.) is a cereal crop highly tolerant to environmental stresses, including abiotic and biotic stresses (e.g., fungal diseases). Among these fungal diseases, leaf rust (LR) is a major threat to rye production. Despite extensive research, the genetic basis of the rye immune response to LR remains unclear. Results An RNA-seq analysis was conducted to examine the immune response of three unrelated rye inbred lines (D33, D39, and L318) infected with compatible and incompatible Puccinia recondita f. sp. secalis (Prs) isolates. In total, 877 unique differentially expressed genes (DEGs) were identified at 20 and 36 h post-treatment (hpt). Most of the DEGs were up-regulated. Two lines (D39 and L318) had more up-regulated genes than down-regulated genes, whereas the opposite trend was observed for line D33. The functional classification of the DEGs helped identify the largest gene groups regulated by LR. Notably, these groups included several DEGs encoding cytochrome P450, receptor-like kinases, methylesterases, pathogenesis-related protein-1, xyloglucan endotransglucosylases/hydrolases, and peroxidases. The metabolomic response was highly conserved among the genotypes, with line D33 displaying the most genotype-specific changes in secondary metabolites. The effect of pathogen compatibility on metabolomic changes was less than the effects of the time-points and genotypes. Accordingly, the secondary metabolome of rye is altered by the recognition of the pathogen rather than by a successful infection. The results of the enrichment analysis of the DEGs and differentially accumulated metabolites (DAMs) reflected the involvement of phenylpropanoid and diterpenoid biosynthesis as well as thiamine metabolism in the rye immune response. Conclusion Our work provides novel insights into the genetic and metabolic responses of rye to LR. Numerous immune response-related DEGs and DAMs were identified, thereby clarifying the mechanisms underlying the rye response to compatible and incompatible Prs isolates during the early stages of LR development. The integration of transcriptomic and metabolomic analyses elucidated the contributions of phenylpropanoid biosynthesis and flavonoid pathways to the rye immune response to Prs. This combined analysis of omics data provides valuable insights relevant for future research conducted to enhance rye resistance to LR.

Meloidogyne javanica is one of the most widespread and economically important sedentary endoparasites. In this study, a comparative transcriptome analysis of M. javanica between pre-parasitic second-stage juveniles (Pre-J2) and parasitic juveniles (Par-J3/J4) was conducted. A total of 48,698 unigenes were obtained, of which 18,826 genes showed significant differences in expression (p < 0.05). In the differentially expressed genes (DEGs) from transcriptome data at Par-J3/J4 and Pre-J2, a large number of unigenes were annotated to the C-type lectin (CTL, Mg01965), the cathepsin L-like protease (Mi-cpl-1), the venom allergen-like protein (Mi-mps-1), Map-1 and the cellulase (endo-β-1,4-glucanase). Among seven types of lectins found in the DEGs, there were 10 CTLs. The regulatory roles of Mj-CTL-1, Mj-CTL-2 and Mj-CTL-3 in plant immune responses involved in the parasitism of M. javanica were investigated. The results revealed that Mj-CTL-2 could suppress programmed cell death (PCD) triggered by Gpa2/RBP-1 and inhibit the flg22-stimulated ROS burst. In situ hybridization and developmental expression analyses showed that Mj-CTL-2 was specifically expressed in the subventral gland of M. javanica, and its expression was up-regulated at Pre-J2 of the nematode. In addition, in planta silencing of Mj-CTL-2 substantially increased the plant resistance to M. javanica. Moreover, yeast co-transformation and bimolecular fluorescence complementation assay showed that Mj-CTL-2 specifically interacted with the Solanum lycopersicum catalase, SlCAT2. It was demonstrated that M. javanica could suppress the innate immunity of plants through the peroxide system, thereby promoting parasitism. [ABSTRACT FROM AUTHOR]

This article discusses the importance of auxin research in understanding plant development and response to the environment. Auxin is a plant hormone that regulates various aspects of plant growth and development, including patterning, meristem activity, and vasculature differentiation. The article highlights the complex pathways and mechanisms involved in auxin transport and response, as well as its interactions with other phytohormones. The knowledge gained from auxin research can be applied to agriculture and horticulture to develop crops that are more resilient to climate change and require fewer resources. However, the manipulation of auxin must be carefully considered to avoid negative effects on plant growth and fitness. The study of genes and pathways involved in the auxin response can provide valuable targets for crop improvement through genetic manipulation. Overall, auxin research has the potential to contribute to the development of climate-resilient crops and ensure the sustainability of food production in a changing world. [Extracted from the article]

Microorganisms play an important role in the growth and development of a plant throughout its entire life cycle. Recent advances in the methods of molecular biological analysis have expanded our understanding of the composition and functions of plant microbiota (epiphytic, rhizosphere, and endosphere) and the molecular mechanisms associated with specific processes that govern plant-microorganism interactions. This article reviews the types of plant microbial communities, their sources of origin, and species composition, as well as the critical role they play in modulating the plant immune response against phytopathogens, improving the elemental nutrition of plants, scaring away herbivorous animals, producing phytohormones, and enabling plants to thrive under extreme environmental conditions.

Phlomis purpurea grows spontaneously in the southern Iberian Peninsula, namely in cork oak (Quercus suber) forests. In a previous transcriptome analysis, we reported on its immunity against Phytophthora cinnamomi. However, little is known about the involvement of secondary metabolites in the P. purpurea defense response. It is known, though, that root exudates are toxic to this pathogen. To understand the involvement of secondary metabolites in the defense of P. purpurea, a metabolome analysis was performed using the leaves and roots of plants challenged with the pathogen for over 72 h. The putatively identified compounds were constitutively produced. Alkaloids, fatty acids, flavonoids, glucosinolates, polyketides, prenol lipids, phenylpropanoids, sterols, and terpenoids were differentially produced in these leaves and roots along the experiment timescale. It must be emphasized that the constitutive production of taurine in leaves and its increase soon after challenging suggests its role in P. purpurea immunity against the stress imposed by the oomycete. The rapid increase in secondary metabolite production by this plant species accounts for a concerted action of multiple compounds and genes on the innate protection of Phlomis purpurea against Phytophthora cinnamomi. The combination of the metabolome with the transcriptome data previously disclosed confirms the mentioned innate immunity of this plant against a devastating pathogen. It suggests its potential as an antagonist in phytopathogens' biological control. Its application in green forestry/agriculture is therefore possible. [ABSTRACT FROM AUTHOR]

Meloidogyne javanica is one of the most widespread and economically important sedentary endoparasites. In this study, a comparative transcriptome analysis of M. javanica between pre-parasitic second-stage juveniles (Pre-J2) and parasitic juveniles (Par-J3/J4) was conducted. A total of 48,698 unigenes were obtained, of which 18,826 genes showed significant differences in expression (p < 0.05). In the differentially expressed genes (DEGs) from transcriptome data at Par-J3/J4 and Pre-J2, a large number of unigenes were annotated to the C-type lectin (CTL, Mg01965), the cathepsin L-like protease (Mi-cpl-1), the venom allergen-like protein (Mi-mps-1), Map-1 and the cellulase (endo-β-1,4-glucanase). Among seven types of lectins found in the DEGs, there were 10 CTLs. The regulatory roles of Mj-CTL-1, Mj-CTL-2 and Mj-CTL-3 in plant immune responses involved in the parasitism of M. javanica were investigated. The results revealed that Mj-CTL-2 could suppress programmed cell death (PCD) triggered by Gpa2/RBP-1 and inhibit the flg22-stimulated ROS burst. In situ hybridization and developmental expression analyses showed that Mj-CTL-2 was specifically expressed in the subventral gland of M. javanica, and its expression was up-regulated at Pre-J2 of the nematode. In addition, in planta silencing of Mj-CTL-2 substantially increased the plant resistance to M. javanica. Moreover, yeast co-transformation and bimolecular fluorescence complementation assay showed that Mj-CTL-2 specifically interacted with the Solanum lycopersicum catalase, SlCAT2. It was demonstrated that M. javanica could suppress the innate immunity of plants through the peroxide system, thereby promoting parasitism.

Immunity in plants arises from defense regulatory circuits that can be conceptualized as modules. Both the types (and isolates) of pathogen and the repertoire of plant receptors may cause different modules to be activated and affect the magnitude of activation. Two major defense enzymes of Arabidopsis are ALD1 and ICS1/SID2. ALD1 is an aminotransferase needed for producing the metabolites pipecolic acid, hydroxy-pipecolic acid, and possibly other defense signals. ICS1/SID2 produces isochorismate, an intermediate in the synthesis of salicylic acid (SA) and SA-derivatives. Metabolites resulting from the activation of these enzymes are found in petiole exudates and may serve as priming signals for systemic disease resistance in Arabidopsis. Mutants lacking ALD1 are known to have reduced SA accumulation. To further investigate the role of ALD1 in relation to the SA-related module, immunity phenotypes of double mutants that disrupt ALD1 and ICS1/SID2 or SA perception by NPR1 were compared with each single mutant after infection by different Pseudomonas strains. Exudates collected from these mutants after infection were also evaluated for their ability to confer disease resistance when applied to wild-type plants. During infection with virulent or attenuated strains, the loss of ALD1 does not increase the susceptibility of npr1 or sid2 mutants, suggesting the main role of ALD1 in this context is in amplifying the SA-related module. In contrast, after an infection that leads to strong pathogen recognition via the cytoplasmic immune receptor RPS2, ALD1 acts additively with both NPR1 and ICS1/SID2 to suppress pathogen growth. The additive effects are observed in early basal defense responses as well as SA-related events. Thus, there are specific conditions that dictate whether the modules independently contribute to immunity to provide additive protection during infection. In the exudate experiments, intact NPR1 and ICS1/SID2, but not ALD1 in the donor plants were needed for conferring immunity. Mixing exudates showed that loss of SID2 yields exudates that suppress active exudates from wild-type or ald1 plants. This indicates that ICS1/SID2 may not only lead to positive defense signals, but also prevent a suppressive signal(s). [ABSTRACT FROM AUTHOR]

Plants, as sessile organisms, must adapt to environmental changes and defend themselves against biotic stress, including pathogen attack. Their immune responses entail recognition of pathogen patterns, activation of defense mechanisms, and accumulation of various antimicrobial compounds. Eugenol, abundant in basil, has antibacterial properties and enhances plant resistance to viruses. However, its priming effects on biotrophic pathogens remain unclear. Thus, we investigated whether eugenol and basil essential oils could prime Arabidopsis thaliana immunity against the hemi-biotroph Pseudomonas syringae pv. maculicola (Psm) MAFF302723. Our study revealed that both eugenol and basil essential oils functioned as priming agents, mitigating disease symptoms upon Psm infection. This priming effect occurred via NPR1-dependent but salicylic acid-independent signaling. Moreover, our gene expression analysis suggested that priming might influence jasmonic acid/ethylene signaling. These findings underscore the potential of employing natural compounds such as basil essential oil to bolster plant immune responses in sustainable agricultural practices., (© The Author(s) 2024. Published by Oxford University Press on behalf of Japan Society for Bioscience, Biotechnology, and Agrochemistry.)

Phlomis purpurea grows spontaneously in the southern Iberian Peninsula, namely in cork oak (Quercus suber) forests. In a previous transcriptome analysis, we reported on its immunity against Phytophthora cinnamomi. However, little is known about the involvement of secondary metabolites in the P. purpurea defense response. It is known, though, that root exudates are toxic to this pathogen. To understand the involvement of secondary metabolites in the defense of P. purpurea, a metabolome analysis was performed using the leaves and roots of plants challenged with the pathogen for over 72 h. The putatively identified compounds were constitutively produced. Alkaloids, fatty acids, flavonoids, glucosinolates, polyketides, prenol lipids, phenylpropanoids, sterols, and terpenoids were differentially produced in these leaves and roots along the experiment timescale. It must be emphasized that the constitutive production of taurine in leaves and its increase soon after challenging suggests its role in P. purpurea immunity against the stress imposed by the oomycete. The rapid increase in secondary metabolite production by this plant species accounts for a concerted action of multiple compounds and genes on the innate protection of Phlomis purpurea against Phytophthora cinnamomi. The combination of the metabolome with the transcriptome data previously disclosed confirms the mentioned innate immunity of this plant against a devastating pathogen. It suggests its potential as an antagonist in phytopathogens’ biological control. Its application in green forestry/agriculture is therefore possible.

Plants perceive an assortment of external cues during their life cycle, including abiotic and biotic stressors. Biotic stress from a variety of pathogens, including viruses, oomycetes, fungi, and bacteria, is considered to be a substantial factor hindering plant growth and development. To hijack the host cell's defence machinery, plant pathogens have evolved sophisticated attack strategies mediated by numerous effector proteins. Several studies have indicated that plasmodesmata (PD), symplasmic pores that facilitate cell‐to‐cell communication between a cell and neighbouring cells, are one of the targets of pathogen effectors. However, in contrast to plant‐pathogenic viruses, reports of fungal‐ and bacterial‐encoded effectors that localize to and exploit PD are limited. Surprisingly, a recent study of PD‐associated bacterial effectors has shown that a number of bacterial effectors undergo cell‐to‐cell movement via PD. Here we summarize and highlight recent advances in the study of PD‐associated fungal/oomycete/bacterial effectors. We also discuss how pathogen effectors interfere with host defence mechanisms in the context of PD regulation. [ABSTRACT FROM AUTHOR]

One of the earliest hallmarks of plant immune response is production of reactive oxygen species (ROS) in different subcellular compartments, which regulate plant immunity. A suitable equilibrium, which is crucial to prevent ROS overaccumulation leading to oxidative stress, is maintained by salicylic acid (SA), a chief regulator of ROS. However, ROS not only act downstream of SA signaling, but are also proposed to be a central component of a self-amplifying loop that regulates SA signaling as well as the interaction balance between different phytohormones. The exact role of this crosstalk, the position where SA interferes with ROS signaling and ROS interferes with SA signaling and the outcome of this regulation, depend on the origin of ROS but also on the pathosystem. The precise spatiotemporal regulation of organelle-specific ROS and SA levels determine the effectiveness of pathogen arrest and is therefore crucial for a successful immune response. However, the regulatory interplay behind still remains poorly understood, as up until now, the role of organelle-specific ROS and SA in hypersensitive response (HR)-conferred resistance has mostly been studied by altering the level of a single component. In order to address these aspects, a sophisticated combination of research methods for monitoring the spatiotemporal dynamics of key players and transcriptional activity in plants is needed and will most probably consist of biosensors and precision transcriptomics. [ABSTRACT FROM AUTHOR]

Calcium (Ca2+) signaling in plant cells is an essential and early event during plant-microbe interactions. The recognition of microbe-derived molecules activates Ca2+ channels or Ca2+ pumps that trigger a transient increase in Ca2+ in the cytoplasm. The Ca2+ binding proteins (such as CBL, CPK, CaM, and CML), known as Ca2+ sensors, relay the Ca2+ signal into down-stream signaling events, e.g., activating transcription factors in the nucleus. For example, CaM and CML decode the Ca2+ signals to the CaM/CML-binding protein, especially CaM-binding transcription factors (AtSRs/CAMTAs), to induce the expressions of immune-related genes. In this review, we discuss the recent breakthroughs in down-stream Ca2+ signaling as a dynamic process, subjected to continuous variation and gradual change. AtSR1/CAMTA3 is a CaM-mediated transcription factor that represses plant immunity in non-stressful environments. Stress-triggered Ca2+ spikes impact the Ca2+-CaM-AtSR1 complex to control plant immune response. We also discuss other regulatory mechanisms in which Ca2+ signaling activates CPKs and MAPKs cascades followed by regulating the function of AtSR1 by changing its stability, phosphorylation status, and subcellular localization during plant defense. [ABSTRACT FROM AUTHOR]

Abstract Reactive oxygen species (ROS) signaling plays a central role in plant immune response. BPAs, referred to as binding partner 1 of accelerated cell death 11 (ACD11) (BPA1) and BPA1-like proteins, regulate ROS-mediated defense responses in Arabidopsis thaliana. However, their distribution and evolutionary characteristics in the plant lineage remain unexplored. In this study, we demonstrated that most BPA genes form a plant-specific family with expansion events observed. We found that BPA and ACD11 genes co-exist in all land plants, suggesting that this immune regulatory module may originate at the early stage of land plant emergence and contribute to their colonization. Angiosperm BPAs can be classified into four distinct groups (I-IV) in our analysis. Domain organization and motif composition are highly conserved within each group but divergent across different groups. In certain species, BPAs undergo complex alternative splicing, suggesting their regulatory and functional divergence. The protein-protein interaction network we constructed predicted additional acting partners of BPAs. The yeast two-hybrid assay revealed 15 BPA interaction pairs forming homo- or hetero-dimers. Taken together, our results provide the first synopsis of BPA evolutionary pattern and adaptations to green plant colonization.

Rapid plant immune responses in the appropriate cells are needed for effective defense against pathogens. Although transcriptome analysis is often used to describe overall immune responses, collection of transcriptome data with sufficient resolution in both space and time is challenging. We reanalyzed public Arabidopsis time-course transcriptome data obtained after low-dose inoculation with a Pseudomonas syringae strain expressing the effector AvrRpt2, which induces effector-triggered immunity in Arabidopsis. Double-peak time-course patterns are prevalent among thousands of upregulated genes. We implemented a multi-compartment modeling approach to decompose the double-peak pattern into two single-peak patterns for each gene. The decomposed peaks reveal an "echoing" pattern: the peak times of the first and second peaks correlate well across most upregulated genes. We demonstrated that the two peaks likely represent responses of two distinct cell populations that respond either cell autonomously or indirectly to AvrRpt2. Thus, the peak decomposition has extracted spatial information from the time-course data. The echoing pattern also indicates a conserved transcriptome response with different initiation times between the two cell populations despite different elicitor types. A gene set highly overlapping with the conserved gene set is also upregulated with similar kinetics during pattern-triggered immunity. Activation of a WRKY network via different entry-point WRKYs can explain the similar but not identical transcriptome responses elicited by different elicitor types. We discuss potential benefits of the properties of the WRKY activation network as an immune signaling network in light of pressure from rapidly evolving pathogens., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Calcium (Ca2+) signalling regulates salicylic acid (SA)‐mediated immune response through calmodulin‐meditated transcriptional activators, AtSRs/CAMTAs, but its mechanism is not fully understood. Here, we report an AtSR1/CAMTA3‐mediated regulatory mechanism involving the expression of the SA receptor, NPR1. Results indicate that the transcriptional expression of NPR1 was regulated by AtSR1 binding to a CGCG box in the NPR1 promotor. The atsr1 mutant exhibited resistance to the virulent strain of Pseudomonas syringae pv. tomato (Pst), however, was susceptible to an avirulent Pst strain carrying avrRpt2, due to the failure of the induction of hypersensitive responses. These resistant/susceptible phenotypes in the atsr1 mutant were reversed in the npr1 mutant background, suggesting that AtSR1 regulates NPR1 as a downstream target during plant immune response. The virulent Pst strain triggered a transient elevation in intracellular Ca2+ concentration, whereas the avirulent Pst strain triggered a prolonged change. The distinct Ca2+ signatures were decoded into the regulation of NPR1 expression through AtSR1's IQ motif binding with Ca2+‐free‐CaM2, while AtSR1's calmodulin‐binding domain with Ca2+‐bound‐CaM2. These observations reveal a role for AtSR1 as a Ca2+‐mediated transcription regulator in controlling the NPR1‐mediated plant immune response. Calcium signalling regulates salicylic acid (SA)‐mediated immune response through calmodulin‐meditated transcriptional activators, AtSRs/CAMTAs, but its mechanism is not clearly understood. Here, we report an AtSR1/CAMTA3‐mediated regulatory mechanism involving the expression of the SA receptor, NPR1. These observations reveal an additional mechanism for controlling the NPR1‐mediated plant immune response. A better understanding of plant immunity should help in modern agriculture. Hence, this topic is of major interest to plant scientists. The Arabidopsis thaliana lines used in this study are wild‐type (WT) Columbia (Col‐0) and loss‐of‐function atsr1 mutant (Salk_001152C). [ABSTRACT FROM AUTHOR]

Cerato-platanins (CPs) form a family of fungal small-secreted cysteine-rich proteins (SSCPs) and are of particular interest not only because of their surface activity but also their abundant secretion by fungi. We performed an evolutionary analysis for 283 CPs from 157 fungal genomes with the focus on the opportunistic plant-beneficial and mycoparasitic fungus Trichoderma. Our results revealed the long evolutionary history of CPs in Dikarya fungi that have undergone several events of lateral gene transfer and gene duplication. Three genes were maintained in the core genome of Trichoderma, while some species have up to four CP encoding genes. All Trichoderma CPs evolve under stabilizing natural selection pressure. The functional analysis of CPs in T. guizhouense and T. harzianum revealed that only EPL1 is active at all stages of the development but plays a minor role in interactions with other fungi and bacteria. The deletion of this gene results in increased colonization of tomato roots by Trichoderma spp. Similarly, the biochemical tests of the heterologously produced EPL1 by Pichia pastoris support the above claims. Based on the obtained results, we conclude that the function of CPs is probably linked to their surfactant properties and the ability to modify the hyphosphere of submerged mycelium and thus facilitate the nutritional versatility of fungi. The effector-like properties do not sufficiently describe the diversity and evolution of these proteins in fungi as they are also maintained, duplicated, or laterally transferred in the genomes of non-herbivore fungi. [ABSTRACT FROM AUTHOR]

Aim Trichoderma guizhouense: NJAU 4742 (Tgui) can serve as a promising strain for the development of novel biofertilizers and biofungicides. Plants primed with Tgui via inoculation were investigated to clarify the underlying mechanisms that promote root growth and development and activate the plant innate immune response. Methods: The relative expression of defence-related genes and of genes involved in the auxin signalling pathway in Zea mays and Arabidopsis thaliana was quantified. Scanning electron microscopy (SEM) was performed to visualize the colonization of Tgui in maize roots, and a proteomic approach was used to identify Tgui-derived elicitors. Results: The establishment of Tgui in the rhizosphere of maize leads to the stimulation of the auxin synthesis pathway in maize and subsequently leads to increased plant growth. And the extracellular proteins of Tgui induced systemic resistance (ISR) of maize plants to Fusarium verticillioides (Fv) (Hypocreales, Ascomycota); the ISR of maize plants may be linked to the accumulation of reactive oxygen species (ROS) and increased deposition of callose in maize tissue. Conclusions: Activation of the maize immune response was triggered by the mixture of extracellular proteins secreted by Tgui into the rhizosphere. Our study thereby contributes to a better understanding of the interaction between T. guizhouense and plant roots. [ABSTRACT FROM AUTHOR]

Plants, as sessile organisms, have adapted a fine sensing system to monitor environmental changes, therefore allowing the regulation of their responses. As the interaction between plants and environmental changes begins at the surface, these changes are detected by components in the plasma membrane, where a molecule receptor generates a lipid signaling cascade via enzymes, such as phospholipases (PLs). Phospholipids are the key structural components of plasma membranes and signaling cascades. They exist in a wide range of species and in different proportions, with conversion processes that involve hydrophilic enzymes, such as phospholipase-C (PLC), phospholipase-D (PLD), and phospholipase-A (PLA). Hence, it is suggested that PLC and PLD are highly conserved, compared to their homologous genes, and have formed clusters during their adaptive history. Additionally, they generate responses to different functions in accordance with their protein structure, which should be reflected in specific signal transduction responses to environmental stress conditions, including innate immune responses. This review summarizes the phospholipid systems associated with signaling pathways and the innate immune response.

Highlights • Lipases belonging to the α/β-hydrolase superfamily are structurally diverse. • Lipases are expressed and activated in plant cells upon pathogen infection. • Lipases play distinct roles in plant-microbe interactions. • Plant immunity involves the regulation of defense-associated lipases. Abstract When facing microbe invaders, plants activate genetic and metabolic defense mechanisms and undergo extracellular and intracellular changes to obtain a certain level of host resistance. Dynamic adjustment and adaptation occur in structures containing lipophilic compounds and cellular metabolites. Lipids encompassing fatty acids, fatty acid-based polymers, and fatty acid derivatives are part of the fundamental architecture of cells and tissues and are essential compounds in numerous biological processes. Lipid-associated plant defense responses are mostly facilitated by the activation of lipases (lipid hydrolyzing proteins), which cleave or transform lipid substrates in various subcellular compartments. In this review, several types of plant defense-associated lipases are described, including their molecular aspects, enzymatic actions, cellular functions, and possible functional relevance in plant defense. Defensive roles are discussed considering enzyme properties, lipid metabolism, downstream regulation, and phenotypic traits in loss-of-function mutants. [ABSTRACT FROM AUTHOR]

Bax-inhibitor 1 (BI-1) is a cell death suppressor conserved in all eukaryotes that modulates cell death in response to abiotic stress and pathogen attack in plants. However, little is known about its role in the establishment of symbiotic interactions. Here, we demonstrate the functional relevance of an Arabidopsis thaliana BI-1 homolog (PvBI-1a) to symbiosis between the common bean (Phaseolus vulgaris) and Rhizobium tropici. We show that the changes in expression of PvBI-1a observed during early symbiosis resemble those of some defence response-related proteins. By using gain- and loss-of-function approaches, we demonstrate that the overexpression of PvBI-1a in the roots of common bean increases the number of rhizobial infection events (and therefore the final number of nodules per root), but induces the premature death of nodule cells, affecting their nitrogen fixation efficiency. Nodule morphological alterations are known to be associated with changes in the expression of genes tied to defence, autophagy, and vesicular trafficking. Results obtained in the present work suggest that BI-1 has a dual role in the regulation of programmed cell death during symbiosis, extending our understanding of its critical function in the modulation of host immunity while responding to beneficial microbes. [ABSTRACT FROM AUTHOR]

Biosensors are indispensable tools to understand a plant’s immunity as its spatiotemporal dimension is key in withstanding complex plant immune signaling. The diversity of genetically encoded biosensors in plants is expanding, covering new analytes with ever higher sensitivity and robustness, but their assortment is limited in some respects, such as their use in following biotic stress response, employing more than one biosensor in the same chassis, and their implementation into crops. In this review, we focused on the available biosensors that encompass these aspects. We show that in vivo imaging of calcium and reactive oxygen species is satisfactorily covered with the available genetically encoded biosensors, while on the other hand they are still underrepresented when it comes to imaging of the main three hormonal players in the immune response: salicylic acid, ethylene and jasmonic acid. Following more than one analyte in the same chassis, upon one or more conditions, has so far been possible by using the most advanced genetically encoded biosensors in plants which allow the monitoring of calcium and the two main hormonal pathways involved in plant development, auxin and cytokinin. These kinds of biosensor are also the most evolved in crops. In the last section, we examine the challenges in the use of biosensors and demonstrate some strategies to overcome them.

Reactive oxygen species (ROS) are known to be important signal molecules that are involved in biotic and abiotic stress responses as well as in growth regulation. However, the molecular mechanisms by which ROS act as a growth regulator, as well as how ROSdependent growth regulation relates to its roles in stress responses, are not well understood. We performed a time-course microarray analysis of Arabidopsis root tips upon treatment with hydrogen peroxide, which we named "ROS-map." Using the ROSmap, we identified an MYB transcription factor, MYB30, which showed a strong response to ROS treatment and is the key regulator of a gene network that leads to the hydrogen peroxidedependent inhibition of root cell elongation. Intriguingly, this network contained multiple genes involved in very-long-chain fatty acid (VLCFA) transport. Finally, we showed that MYB30 is necessary for root growth regulation during defense responses, thus providing a molecular link between these two ROS-associated processes. [ABSTRACT FROM AUTHOR]

Many plant pathogens secrete virulence effectors into host cells to target important proteins in host cellular network. However, the dynamic interactions between effectors and host cellular network have not been fully understood. Here, an integrative network analysis was conducted by combining Arabidopsis thaliana protein–protein interaction network, known targets of Pseudomonas syringae and Hyaloperonospora arabidopsidis effectors, and gene expression profiles in the immune response. In particular, we focused on the characteristic network topology of the effector targets and differentially expressed genes (DEGs). We found that effectors tended to manipulate key network positions with higher betweenness centrality. The effector targets, especially those that are common targets of an individual effector, tended to be clustered together in the network. Moreover, the distances between the effector targets and DEGs increased over time during infection. In line with this observation, pathogen-susceptible mutants tended to have more DEGs surrounding the effector targets compared with resistant mutants. Our results suggest a common plant–pathogen interaction pattern at the cellular network level, where pathogens employ potent local impact mode to interfere with key positions in the host network, and plant organizes an in-depth defense by sequentially activating genes distal to the effector targets.

Kinases facilitate detection of extracellular signals and set in motion cellular responses for plant adaptation and survival. Some of the energy utilized for kinase signal processing is produced through the activity of ion transporters. Additionally, the synergy between cellular ions and signal transduction influences plant response to pathogens, and their growth and development. In plants, the signaling elements that connect cell wall and membrane sensors with ion homeostasis and transport-mediated processes are largely unknown. Current research indicates that plant Integrin-Linked Kinases (ILKs), a subfamily Raf-like MAP2K Kinases, may have evolved to fulfill this role. In this review, we explore new findings on plant ILKs placing a particular focus on the connection between ILKs proteins unique structural features and ILKs functions. The ankyrin repeat motifs and the kinase domains of ILKs in Arabidopsis and land plants lineage, respectively, are analyzed and discussed as potential determinants of ILKs' metal ion cofactor specificity and their enzymatic and interaction activities. Further, ILKs regulation through gene expression, subcellular localization, and ions and ion transporters is reviewed in the context of recent studies. Finally, using evidence from literature and interactomics databanks, we infer ILKs-dependent cellular pathways and highlight their potential in transmitting multiple types of signals originating at the interface between the cell wall and plasma membrane. [ABSTRACT FROM AUTHOR]

Tomatoes are one of the most important vegetables thanks to their taste attributes and nutritional value. Their cultivation is threatened by various pathogens including viruses. The application of resistance inducers (RI), such as benzo(1,2,3)-thiadiazole-7-carbothioic acid S -methyl ester (BTH) may be used to enhance plant performance against viruses. Here we aimed to compare the impact of BTH and its choline derivative (Chol-BTH) on resistance induction and antioxidant properties of healthy plants and tomato mosaic virus (ToMV)-infected ones. The response of tomato plants to treatment with BTH or Chol-BTH was manifested by increased expression of not only pathogenesis-related ( PR ) genes but also WRKY and Jasmonate Zim-domain protein ( JAZ ) genes and increased jasmonic acid (JA) levels. The effect of BTH as a resistance inducer was observed early after application, while with Chol-BTH the plant defense system reacted more strongly after 8 days. The antioxidant properties of RI-treated tomatoes are related to both glutathione content and peroxidase activity. In the case of BTH, an increase in these activities occurred early after application, while in the case of Chol-BTH, the glutathione level was particularly high in the plant early after treatment, and high peroxidase activity was observed 8 days post-treatment. Overall, the collected results indicate that Chol-BTH, due to its physicochemical parameters (e.g., good solubility) and biological activity (increased expression of lignification-related genes, supported by increases in peroxidase activity and total phenolic compounds levels), can also be a very useful agent inducing tomato resistance against viral pathogens.

Deciphering plant-microbe interactions is a promising aspect to understand the benefits and the pathogenic effect of microbes and crop improvement. The advancement in sequencing technologies and various ‘omics’ tool has impressively accelerated the research in biological sciences in this area. The recent and ongoing developments provide a unique approach to describing these intricate interactions and test hypotheses. In the present review, we discuss the role of plant-pathogen interaction in crop improvement. The plant innate immunity has always been an important aspect of research and leads to some interesting information like the adaptation of unique immune mechanisms of plants against pathogens. The development of new techniques in the post - genomic era has greatly enhanced our understanding of the regulation of plant defense mechanisms against pathogens. The present review also provides an overview of beneficial plant-microbe interactions with special reference to Agrobacterium tumefaciens-plant interactions where plant derived signal molecules and plant immune responses are important in pathogenicity and transformation efficiency. The construction of various Genome-scale metabolic models of microorganisms and plants presented a better understanding of all metabolic interactions activated during the interactions. This review also lists the emerging repertoire of phytopathogens and its impact on plant disease resistance. Outline of different aspects of plant-pathogen interactions is presented in this review to bridge the gap between plant microbial ecology and their immune responses.

The recognition of pathogen effectors by their cognate nucleotide-binding leucine-rich repeat (NLR) receptors activates effector-triggered immunity (ETI) in plants. ETI is associated with correlated transcriptional and translational reprogramming and subsequent death of infected cells. Whether ETI-associated translation is actively regulated or passively driven by transcriptional dynamics remains unknown. In a genetic screen using a translational reporter, we identified CDC123, an ATP-grasp protein, as a key activator of ETI-associated translation and defense. During ETI, an increase in ATP concentration facilitates CDC123-mediated assembly of the eukaryotic translation initiation factor 2 (eIF2) complex. Because ATP is required for the activation of NLRs as well as the CDC123 function, we uncovered a possible mechanism by which the defense translatome is coordinately induced during NLR-mediated immunity. The conservation of the CDC123-mediated eIF2 assembly suggests its possible role in NLR-mediated immunity beyond plants. [Display omitted] • Effector-triggered immunity (ETI) elevates global translational activity • A genetic screen identifies CDC123 as a positive regulator of translation during ETI • Translation initiation factor eIF2γ interacts with CDC123 and positively regulates ETI • ATP increase during ETI enhances CDC123-mediated eIF2 complex assembly and translation Chen et al. identify CDC123 as a key activator of protein translation during effector-triggered immunity (ETI) in plants. Elevated ATP concentration during ETI facilitates CDC123-mediated assembly of the eIF2 complex to promote translation. Conservation of CDC123-mediated eIF2 assembly suggests its possible role in NLR-mediated immunity beyond plants. [ABSTRACT FROM AUTHOR]

Deciphering plant-microbe interactions is a promising aspect to understand the benefits and the pathogenic effect of microbes and crop improvement. The advancement in sequencing technologies and various 'omics' tool has impressively accelerated the research in biological sciences in this area. The recent and ongoing developments provide a unique approach to describing these intricate interactions and test hypotheses. In the present review, we discuss the role of plant-pathogen interaction in crop improvement. The plant innate immunity has always been an important aspect of research and leads to some interesting information like the adaptation of unique immune mechanisms of plants against pathogens. The development of new techniques in the post -- genomic era has greatly enhanced our understanding of the regulation of plant defense mechanisms against pathogens. The present review also provides an overview of beneficial plant-microbe interactions with special reference to Agrobacterium tumefaciens-plant interactions where plant derived signal molecules and plant immune responses are important in pathogenicity and transformation efficiency. The construction of various Genome-scale metabolic models of microorganisms and plants presented a better understanding of all metabolic interactions activated during the interactions. This review also lists the emerging repertoire of phytopathogens and its impact on plant disease resistance. Outline of different aspects of plant-pathogen interactions is presented in this review to bridge the gap between plant microbial ecology and their immune responses. [ABSTRACT FROM AUTHOR]

Salicylic acid ( SA) plays an important role in various aspects of plant development and responses to stresses. To elucidate the sophisticated regulatory mechanism of SA synthesis and signaling, we used a yeast one-hybrid system to screen for regulators of ISOCHORISMATE SYNTHASE 1 ( ICS1), a gene encoding the key enzyme in SA biosynthesis in Arabidopsis thaliana. A TCP family transcription factor At TCP8 was initially identified as a candidate regulator of ICS1. The regulation of ICS1 by TCP proteins is supported by the presence of a typical TCP binding site in the ICS1 promoter. The binding of TCP8 to this site was confirmed by in vitro and in vivo assays. Expression patterns of TCP8 and its corresponding gene TCP9 largely overlapped with ICS1 under pathogen attack. A significant reduction in the expression of ICS1 during immune responses was observed in the tcp8 tcp9 double mutant. We also detected strong interactions between TCP8 and SAR deficient 1 (SARD1), WRKY family transcription factor 28 (WRKY28), NAC (NAM/ATAF1,ATAF2/CUC2) family transcription factor 019 (NAC019), as well as among TCP8, TCP9 and TCP20, suggesting a complex coordinated regulatory mechanism underlying ICS1 expression. Our results collectively demonstrate that TCP proteins are involved in the orchestrated regulation of ICS1 expression, with TCP8 and TCP9 being verified as major representatives. [ABSTRACT FROM AUTHOR]