Search Results (96)

Huanglongbing (HLB), caused by Candidatus Liberibacter asiaticus (CLas) and vectored by Asian citrus psyllid (Diaphorina citri), remains a major constraint to sustainable citrus production. In Florida, individual protective covers (IPCs) have been adopted as an effective psyllid exclusion tool by shielding young trees from this vector of the phloem-dwelling bacterium CLas. Brassinosteroids (BRs), a class of plant steroid hormones, are being explored as a treatment to mitigate HLB and are approved for commercial use in the state. We investigated the effect of IPCs combined with homobrassinolide (HBr) applied as a foliar spray on CLas titer, canopy volume, tree growth, yield, fruit quality, and defense-related gene expression of the salicylic acid (SA) pathways in ‘Tango’ mandarin grafted on sour orange (SO) or US-942 rootstocks. After being covered with IPCs in the field for three years, trees were subjected to monthly foliar application of HBr upon IPC removal. The experiment included four treatment groups: trees with IPC and HBr spray (IPC HBr+), IPC without HBr (IPC HBr-), no-IPC with HBr (no-IPC HBr+), and no-IPC without HBr (no-IPC HBr-). IPCs effectively delayed bacterial infection for six to nine months after IPC removal, maintaining higher cycle threshold (Ct) values (lower CLas titers) than in no-IPC trees, confirming the protective effect of IPCs against early CLas colonization. The combination of IPCs and HBr spray significantly enhanced canopy volume, particularly in trees grafted on SO. This effect was sustained over one year and was consistently greater in IPC HBr+ trees than in IPC HBr- and no-IPC HBr+ or HBr- trees, suggesting a synergistic effect of the combined therapy on enhancing tree growth. The tree height and trunk diameter were primarily improved by IPC, regardless of HBr treatment. IPC-treated trees exhibited significantly greater height and trunk diameters (scion and rootstock) than no-IPC trees across one or both rootstocks, indicating that IPCs alone contribute to these horticultural growth improvements. IPC trees also showed reduced preharvest fruit drop compared to the no-IPCs trees, resulting in higher yields, with additional gains observed in IPC HBr+ trees on SO. Fruit quality attributes, including °Brix, titratable acidity, peel color, and size, did not differ significantly among treatments. Importantly, gene expression analysis revealed early and sustained upregulation of key SA pathway genes in IPC HBr+ trees, indicating that HBr effectively activated systemic acquired resistance (SAR), particularly on SO rootstock. This study highlights the complementary roles of IPCs and HBr in the management of HLB. While IPCs provided essential early protection against CLas and promoted long-term horticultural growth, HBr enhanced early canopy development, activated host defense mechanisms, and enhanced yield. The integration of both approaches offers a sustainable and effective strategy to protect young citrus trees, delay CLas infection, and improve tree health and productivity under endemic HLB. Full article

Dark-induced senescence (DIS) is a coordinated physiological process associated with chlorophyll degradation, macromolecular turnover, and nutrient remobilization under prolonged darkness. EXO70B1, a subunit of the exocyst complex, has been implicated in intracellular membrane trafficking, autophagy-associated vacuolar transport, and salicylic acid-dependent immunity. However, whether EXO70B1 contributes to DIS remains unknown. Here, we show that EXO70B1 expression increases with leaf age and is transiently induced during the early phase of dark treatment. Accordingly, as a consequence of loss of EXO70B1, an acceleration of dark-induced leaf yellowing, chlorophyll degradation, and decline in photosynthetic performance was observed. Notably, this hypersensitivity was strongly age-dependent, being evident in mature (4-week-old) plants but not in younger plants. Genetic analyses indicated that the accelerated chlorophyll degradation in the EXO70B1 mutant background depends on NYE1 function. To investigate the molecular basis underlying this age-specific transition, we performed stage-resolved transcriptomic profiling, which identified the 4-week stage as a major point of divergence between Col-0 and exo70b1-1. Before visible necrosis, mature exo70b1-1 leaves displayed substantial transcriptional reprogramming, including enrichment of salicylic acid (SA) signaling, systemic acquired resistance (SAR), and other defense-related pathways. Collectively, our findings support a role for EXO70B1 as an age-dependent modulator of DIS and indicate that the enhanced dark sensitivity of mature exo70b1-1 leaves is associated with defense-related transcriptional reprogramming and NYE1-dependent chlorophyll degradation. Full article

Fungal endophytes are symbiotic microorganisms that establish strong relationships inside plant tissues, providing potential advantages, especially in grasses, by enhancing tolerance to both abiotic and biotic stresses. This review investigates the molecular mechanisms through which fungal endophytes mediate stress tolerance, targeting host–pathogen interactions. By modulating pathogen-associated molecular patterns (PAMPs), damage-associated molecular patterns (DAMPs), and effector proteins, fungal endophytes may contribute to priming the plant’s immune system, enhancing its resistance to pathogen invasion. Moreover, endophyte colonization regulates core processes such as osmotic regulation, reactive oxygen species (ROS) detoxification, and secondary metabolite biosynthesis that enable plants to tolerate environmental stresses like drought, heat, and salinity. The review highlights the impact of endophytes on immune priming, systemic acquired resistance (SAR), and the regulation of non-coding RNAs that regulate host gene networks associated with stress tolerance. Furthermore, the integration of advanced multi-omics techniques genomics, transcriptomics, proteomics, metabolomics, and fluxomics has revealed emerging insights into the genetic and metabolic pathways driving these symbiotic associations. However, grass-specific molecular datasets remain limited, and the consistency of endophyte-mediated tolerance across host species and environmental conditions is not yet fully resolved. Fungal endophytes increase grass stress resilience through coordinated pathogen recognition, RNA regulation, and metabolic reprogramming while AI-assisted multi-omics approaches are emerging as tools for identifying candidate regulatory networks, although empirical validation in grass–endophyte systems remains limited. Together, these advances highlight the potential for climate-smart and sustainable crop improvement. Future research integrating functional genomics, field validation, and biosafety assessment will be essential for translating endophyte-based strategies into reliable agricultural applications. Full article

Salicylic acid (SA) is a key endogenous regulator involved in plant defense responses to biotic and abiotic stresses. The increasing resistance of pathogens to chemical plant protection products and growing environmental restrictions have intensified the search for alternative strategies to enhance plant health and stress tolerance. Among these strategies, the induction of natural defense mechanisms, in which SA plays a central signaling role, has gained particular attention. This review summarizes current knowledge on the role of SA in shaping plant resistance to environmental factors. The fundamental mechanisms of plant defense, including innate immunity, induced systemic resistance (ISR), and systemic acquired resistance (SAR), are discussed, with emphasis on the signaling function of SA and its interaction with other phytohormones, especially jasmonic acid and ethylene. The role of SA in regulating physiological processes associated with stress tolerance, such as antioxidant system activity, photosynthesis, plant growth, and senescence, is highlighted. The review of research results indicates that appropriately selected doses and timing of SA treatments can enhance resistance to selected pathogens and improve plant tolerance to adverse environmental conditions. However, treatment effectiveness depends on multiple factors, particularly SA concentration and plant–pathogen interactions. Salicylic acid is a promising component of integrated and sustainable plant protection strategies. Further research, especially under field conditions, is necessary to optimize its practical use and fully determine its potential in modern agriculture. Full article

Clinical, experimental, and computational evidence of COVID-19 virulence and infectivity has been linked to SARS-CoV-2 shell disorder. A strong link was first discovered using an AI disorder-predicting tool, which detected an unusually hard (low disorder) outer shell among all SARS-CoV-2-related viruses but not in the 2003 SARS-CoV-1. This could account for the high infectivity found in SARS-CoV-2—but not in SARS-CoV-1—as it is believed that hard shells protect viral particles from the onslaught of the antimicrobial enzymes present in the respiratory system and saliva. As a result, much larger quantities of particles are shed by COVID-19 patients. Abnormally hard outer shells (M) are associated with burrowing animals, e.g., pangolins, and SARS-CoV-2 likely acquired these shells due to its long-term evolutionary interactions with pangolins. As for virulence, the inner shell of SARS-CoV-2 (N) has been found to exhibit lower disorder than that of SARS-CoV-1. This lower disorder is consistent with the fact that SARS-CoV-2 is less virulent than SARS-CoV-1, as higher disorder in the inner shell is associated with more efficient protein–protein binding during replication. The link between N/M disorder and virulence or infectivity falls under the umbrella of shell disorder models (SDMs), which can connect virulence, infectivity, and long COVID under one coherent concept. Evidence of the reliability and reproducibility of SDMs as applied to COVID-19 is examined. The hard M that is resisting the antimicrobial enzymes in the respiratory system can be extended to immunological enzymes, especially those found in phagocytes such as macrophages, which can therefore become a reservoir for the virus. Full article

Plant defence elicitors have emerged as pivotal components of sustainable fruit crop protection, aligning with One Health principles by reducing chemical residues while enhancing ecosystem and human health. These exogenous agents—ranging from phytohormones, peptides, and cell-wall fragments to botanical extracts—activate or prime innate immune responses in fruit crops through pattern-triggered immunity (PTI), systemic acquired resistance (SAR), and induced systemic resistance (ISR) pathways. Over the last decade, advances in receptor biochemistry, genomics, metabolomics, and epigenetics have transformed this field. Recent mechanistic advances reveal that oligosaccharide elicitors derived from chitosan and laminarin are perceived by membrane-localised pattern recognition receptors (PRRs) that confer broad-spectrum resistance against fungal, bacterial, and viral pathogens in fruits. By contrast, no specific protein receptor has been identified for harpin proteins, the emerging evidence indicating that harpin perception may occur through direct interaction with plasma-membrane lipids or lipid-associated proteins. The One Health approach is supported by elicitors, biodegradability, minimal environmental persistence, and the ability to reduce synthetic fungicide usage by 30–70%. However, challenges remain regarding batch-to-batch variability, sensory acceptance due to bitter compounds, regulatory hurdles for novel food approvals, and the need for optimised application protocols that consider the fruit genotype and developmental stage. The future integration of nanotechnology for targeted delivery, the artificial-intelligence-driven screening of active molecules, and synergistic combinations with biocontrol agents promises to overcome these limitations, positioning plant defence elicitors as cornerstone tools for resilient, health-promoting fruit production systems. Full article

Plant-parasitic nematodes (PPNs) cause big crop losses globally. Safe/reliable methods for their durable management strategies can harness various beneficial relationships among the plant immune system and related microbiomes. Molecular mechanisms basic to these relations reveal wide arrays of significant roles for plant-healthy growth. This review focuses on such relations of microbiomes to prime and immunize plants against PPNs. It also highlights molecular issues facing PPN-resistant varieties with possible solutions such as genetic breeding/engineering, grafting, PPN-antagonistic root exudates, and novel resistant cultivars. These issues call for optimal uses of various widespread groups of microbiomes. Related plant signaling hormones and transcription factors that regulate gene expression and modulate nematode-responsive genes to ease positive/negative adaptation are presented. Exploring PPN-resistance genes, their activation mechanisms, and signaling networks offers a holistic grasp of plant defense related to biotic/abiotic factors. Such factors relevant to systemic acquired resistance (SAR) via plant–microbe interactions to manage PPNs are stressed. The microbiomes can be added as inoculants and/or steering the indigenous rhizosphere ones. Consequently, SAR is mediated by the accumulation of salicylic acid and the subsequent expression of pathogenesis-related genes. To activate SAR, adequate priming and induction of plant defense against PPNs would rely on closely linked factors. They mainly include the engaged microbiome species/strains, plant genotypes, existing fauna/flora, compatibility with other involved biologicals, and methods/rates of the inoculants. To operationalize improved plant resistance and the microbiome’s usage, novel actionable insights for research and field applications are necessary. Synthesis of adequate screening techniques in plant breeding would better use multiple parameters (molecular and classical ones)-based ratings for PPN-host suitability designation. Sound statistical analyses and interpretation approaches can better identify genotypes with high-level, stable resistance to PPNs than the commonly used ones. Linking molecular mechanisms to consistent field relevance can be progressed via dissemination of many advanced techniques. The CRISPR/Cas9 system has been effective in knocking out both the OsHPP04 gene in rice to confer resistance against Meloidogyne graminicola and the GhiMLO3 gene in cotton to minimize the Rotylenchulus reniformis reproduction. Its genetic modifications in crops synthesized “transgene-free” PPN-resistant plants without decreased growth/yield. Characterizing microbiome species/strains needed to prime and immunize plants requires better molecular tools for fine-scale taxonomic resolution than the common ones used. The former can distinguish closely related ones that exhibit divergent phenotypes for key attributes like stability and production of enzymes and secondary metabolites. As PPN-control strategies via tritrophic interactions are more sensitive to the relevant settings than chemical nematicides, it is suggested herein to test these settings on a case-by-case basis to avoid erratic/contradictory results. Moreover, expanding the use of automated systems to expedite detection/count processes of PPN and related microbes with objectivity/accuracy is discussed. When PPNs and their related microbial distribution patterns were modeled, more aspects of their field distributions were discovered in order to optimize their integrated management. Hence, the feasibility of site-specific microbiome application in PPN–hotspot infections can be evaluated. The main technical challenges and controversies in the field are also addressed herein. Their conceptual revision based on harnessing novel techniques/tools is direly needed for future clear trends. This review also engages raising growers’ awareness to leverage such strategies for enhancing plant resistance and advancing the microbiome role. Microbiomes enjoy wide spectrum efficacy, low fitness cost, and inheritance to next generations in durable agriculture. Full article

Mitogen-activated protein kinase kinase kinases (MAPKKKs) are pivotal upstream regulators of MAPK cascades, integrating signals that coordinate plant development and stress responses. However, the specific functions of MAPKKKs, particularly within the MEKK subfamily, in mediating cotton resistance to Verticillium wilt and Fusarium wilt remain poorly characterized. To address this, we conducted a systematic, cross-species analysis of the MAPKKK family in four key cotton species: Gossypium arboreum, Gossypium barbadense, Gossypium hirsutum, and Gossypium raimondii. Genome-wide identification and phylogenetic analysis revealed 660 MAPKKK genes, classifying them into the MEKK, Raf, and ZIK subfamilies. Evolutionary analysis indicated that Whole-Genome Duplication (WGD) events were the primary driver of family expansion. Promoter cis-element and Gene Ontology (GO) enrichment analyses implicated these genes in hormone signaling and stress adaptation. Expression profiling demonstrated functional modularity, with distinct members responding specifically to cold stress or cooperatively to drought and salt stresses. Upon pathogen infection, members diverged into regulatory modules associated with immune homeostasis, tissue-specific defense, and core signaling potentially governing systemic acquired resistance (SAR). The temporal expression patterns of core candidate genes were validated by qRT-PCR. This study provides, for the first time, a comprehensive evolutionary and functional framework for the MEKK subfamily within the cotton MAPKKK family. It reveals the conserved and divergent roles of this subfamily in stress adaptation and identifies key candidate genes for breeding disease-resistant cotton varieties. Full article

The potyvirus helper component proteinase (HcPro) is a multifunctional protein, with one of its most documented functions being host antiviral RNA silencing suppression. This study shows that the HcPro of potato virus Y (PVY), an important member of the potyvirus group, prevents the replication of a related competing secondary virus. This phenomenon, referred to as superinfection exclusion (SIE), is common in bacterial, human, and plant virus infections. We also report that HcPro’s induction of SIE is strain-specific and that this specificity is provided by the first four amino acid residues of the protein. Consistent with the mechanism of SIE, the study found that HcPro does not exclude a resident virus. Additionally, HcPro’s induction of SIE was observed to function independently of its ability to suppress antiviral RNA silencing. HcPro’s induction of SIE is relevant given the prevalence of multiple PVY strains that routinely co-infect the same cell and that may lead to recombination and emergence of new and more virulent strains. Furthermore, cross-protection or systemic acquired resistance (SAR) that is employed in plant virus disease management occurs when SIE moves from the cellular level and spreads systemically, emphasizing the importance of studying SIE. Full article

Sesame bacterial wilt, caused by the pathogen Ralstonia solanacearum, is a major constraint for continuous cropping. Deciphering the defense mechanisms of sesame is therefore essential to the development of novel and effective control strategies. The Non-expressor of Pathogenesis-Related 1 (NPR1) plays a key role in regulating salicylic acid (SA)-mediated systemic acquired resistance (SAR). In this study, we reported that leaf treatments with 50 μg/mL benzothiadiazole (BTH) resulted in increased protection of sesame against Ralstonia solanacearum. We clarified the structure, expression patterns, and function of a NPR1 homologous gene, SiNPR1, in sesame. The SiNPR1 gene open reading frame comprises 1758 bp, and it encodes 585 amino acids. Phylogenetic analysis revealed that SiNPR1 is closely related to NPR1-like in Olea europaea and clustered with other members of the families Monocotyledon and Dicotyledon. Quantitative real-time PCR (qRT-PCR) results demonstrated that the expression of the SiNPR1 gene was organ-specific and could be induced by BTH. The yeast two-hybrid assay confirmed that SiNPR1 directly interacts with SiTGA2. In conclusion, these results suggest that SiNPR1 plays a pivotal role in the BTH-dependent systemic acquired resistance in sesame. Full article

Agriculture is still at serious risk from viral infections, particularly in light of climate change and more intensive farming practices. Small non-coding RNAs (sRNAs), in particular microRNAs (miRNAs) and circular RNAs (circRNAs), have emerged as crucial post-transcriptional regulators of plant antiviral defense in this setting. These molecules provide an essential RNA-based immunity layer by regulating hormones, autophagy, redox balance, immunological signaling, and programmed cell death. In this work, we examine the molecular processes through which circRNAs and miRNAs function during viral infection, focusing on how they affect autophagy and systemic acquired resistance (SAR). Through thorough searches of PubMed, Web of Science, and Scopus, we combined findings from peer-reviewed experimental and transcriptomic studies. Our study covers important crops as well as model species (Arabidopsis thaliana, Nicotiana benthamiana), providing a thorough understanding of sRNA synthesis, target control, and antiviral signaling. By combining previously disparate data, this review provides a coherent framework for understanding how short RNAs affect plant immune responses to viral infections. We highlight key regulatory relationships that need further study and propose that these results can be used as a foundation for new RNA-based biotechnological approaches. By carefully altering RNA regulatory mechanisms, scientists can use this information to help them create more resistant crops. Full article

Active compounds used in agriculture are mainly in the form of acids. This applies primarily to substances that are inducers of systemic acquired resistance, which is one of the most promising methods of supporting plants in the fight against pathogens. The physicochemical properties and biological activity of such substances can be improved by derivatizing them to salt forms. We used the concept of ionic liquids to obtain novel compounds in the form of chlormequat ionic liquids. In this study we present synthesis and characterization of a series of novel ionic liquids composed of the chlormequat cation paired with plant resistance-inducing anions, including salicylic acid and its chlorinated derivatives, nicotinic acid and isonicotinic acid. The results indicate that the new compounds in the form of salts are characterized by better biological activity related to SAR induction and lower phytotoxicity compared to the parent compounds as their equivalents in acid forms. The obtained compounds demonstrated the ability to activate defense responses in tobacco and to reduce susceptibility to viral infection, highlighting their potential for further application in crop protection. Full article

The global surge in multidrug-resistant (MDR) bacterial pathogens has created an urgent imperative for innovative antimicrobial strategies. Enterococcus faecalis, Staphylococcus aureus, and Acinetobacter baumannii demonstrate remarkable antibiotic resistance and dominate hospital-acquired infections. These bacteria often form biofilms, a complex community structure that shields them from immune system phagocytosis, resists antibiotic penetration, and enhances their survival in hostile environments. In clinical cases, these bacteria often form mixed biofilms and lead to treatment failures. Phages and their derivatives have emerged as promising candidates in the fight against drug-resistant bacteria. Lys22, an endolysin derived from an enterococcus phage, has been cloned and demonstrated to possess a broad host range, effectively targeting E. faecalis, various Staphylococcus species, and A. baumannii. When applied to the biofilms formed by these bacteria, Lys22 was found to significantly inhibit both simple and complex biofilms in vitro. Virulent genes, including agrA, sarA, and icaA in S. aureus; asa1, cylA, and gelE in E. faecalis; and OmpA and lpsB in A. baumannii were also downregulated by Lys22. Notably, Lys22 also exhibited a robust protective effect against dual or triple infections involving E. faecalis, S. aureus, and A. baumannii in a zebrafish embryos model, highlighting its potential as a therapeutic agent in combatting multi-bacterial infections. Full article

The COP9 signalosome (CSN) is a highly conserved eukaryotic protein complex that plays a crucial role in plant growth, development, and stress responses by modulating the ubiquitination pathway. Emerging evidence underscores its significance in plant immunity, where it orchestrates diverse defense mechanisms, including hormone signaling, reactive oxygen species (ROS), homeostasis, and secondary metabolite (SM) biosynthesis. As a key regulator, CSN influences multiple layers of immune responses, such as pattern-triggered immunity (PTI), effector-triggered immunity (ETI), and systemic acquired resistance (SAR). However, the intricate interplay between CSN and immune regulatory networks remains incompletely understood, and a comprehensive model of its mechanistic framework is still lacking. This review systematically consolidates current knowledge on CSN-mediated immune regulation in plant–pathogen interactions and highlights its role in disease resistance. Full article

Chili (Capsicum annuum L.) is a herbaceous vegetable grown and consumed worldwide. In Thailand, chili plants are severely hampered by anthracnose disease, leading to severe yield losses. This study aimed to investigate endophytic bacteria (EPB) for their potential as a biocontrol agent and plant growth promoter (PGP). Among a total of 108 isolates, strain KKU-RE-018 was identified by partial 16S rRNA gene sequencing as belonging to the genus Bacillus. This isolate exhibited strong antifungal activity against Colletotrichum capsici; its activity occurred through the production of hydrolytic enzymes, including chitinase and β-1,3-glucanase, and exhibited PGP properties. This endophytic bacterium significantly reduced anthracnose severity compared with the control, achieving a disease reduction index (DRI) of over 60%. Moreover, chili plants treated with the bacterium showed higher plant growth parameters under greenhouse conditions. The levels of phenolic compounds and salicylic acid in plants treated with Bacillus sp. KKU-RE-018 could activate systemic acquired resistance (SAR). Taken together, these findings demonstrate that Bacillus sp. KKU-RE-018 plays a multifaceted role, capable of suppressing anthracnose and simultaneously promoting chili growth. Full article