Pathogenesis-related Research Articles

Identification and Characterization of Neuroprotective Properties of Thaumatin-like Protein 1a from Annurca Apple Flesh Polyphenol Extract.

Alzheimer's disease (AD) and Parkinson's disease (PD) are multifactorial neurodegenerative disorders that are mostly treated with drugs inhibiting key enzymes of cholinergic and aminergic neurotransmission, such as acetyl and butyryl cholinesterase (AChE, BuChE) or monoamine oxidases (MAO)-A/B, and of Aβ1-40 aggregation. Diet plant components with multitarget functions are promising compounds in the prevention of AD and PD. Our aim was to identify neuroprotective compounds from Annurca apple polyphenol extract (AFPE). AFPE was fractionated by gel filtration, and the eluted peaks were subjected to chemical analyses (i.e., RP-HPLC and mass spectrometry), determination of inhibitory enzyme activity and cell effects by MTT, and morphology assays. In AFPE, we identified thaumatin-like protein 1a, belonging to the pathogenesis-related protein (PR) family. This protein showed the best inhibitory activity on AChE, MAO-A (IC50 = 5.53 µM and 1.71 µM, respectively), and Aβ1-40 fibril aggregation (IC50 = 9.16 µM), compared to AFPE and other polyphenol-containing fractions. Among the latter, Peak 4 reverted Aβ fibril formation (IC50 = 104.87 µM). Moreover, thaumatin-like protein 1a protected AGS and MKN-28 cells from serum-deprivation-induced stress conditions. We showed that AFPE exerted neuroprotective functions not only through its polyphenols but also through thaumatin-like protein 1a, which acted like a multitarget molecule.

Valsa mali PR1-like protein modulates an apple valine-glutamine protein to suppress JA signaling-mediated immunity.

Apple Valsa canker (AVC) is a devastating disease of apple (Malus × domestica), caused by Valsa mali (Vm). The Cysteine-rich secretory protein, Antigen 5, and Pathogenesis-related protein 1 (CAP) superfamily protein PATHOGENESIS-RELATED PROTEIN 1-LIKE PROTEIN c (VmPR1c) plays an important role in the pathogenicity of Vm. However, the mechanisms through which it exerts its virulence function in Vm-apple interactions remain unclear. In this study, we identified an apple valine-glutamine (VQ)-motif-containing protein, MdVQ29, as a VmPR1c target protein. MdVQ29-overexpressing transgenic apple plants showed substantially enhanced AVC resistance as compared with the wild type. MdVQ29 interacted with the transcription factor MdWRKY23, which was further shown to bind to the promoter of the jasmonic acid (JA) signaling-related gene CORONATINE INSENSITIVE 1 (MdCOI1) and activate its expression to activate the JA signaling pathway. Disease evaluation in lesion areas on infected leaves showed that MdVQ29 positively modulated apple resistance in a MdWRKY23-dependent manner. Furthermore, MdVQ29 promoted the transcriptional activity of MdWRKY23 toward MdCOI1. In addition, VmPR1c suppressed the MdVQ29-enhanced transcriptional activation activity of MdWRKY23 by promoting the degradation of MdVQ29 and inhibiting MdVQ29 expression and the MdVQ29-MdWRKY23 interaction, thereby interfering with the JA signaling pathway and facilitating Vm infection. Overall, our results demonstrate that VmPR1c targets MdVQ29 to manipulate the JA signaling pathway to regulate immunity. Thus, this study provides an important theoretical basis and guidance for mining and utilizing disease-resistance genetic resources for genetically improving apples.

Potential anticancer agents of Curcuma aeruginosa-based kombucha: In vitro and in silico study

BackgroundThe kombucha is an original drink from China that is traditionally produced from fermentation that rich in polyphenol and act as antioxidants and anticancer. In the times, kombucha is widely combined with several medicinal plants, one of which is Curcuma aeruginosa, an herbal plant used as medicine because it has chemical constituents of saponins, triterpenoids, alkaloids, and flavonoids. Kombucha-based Curcuma aeruginosa is believed to have role as an antioxidant and anticancer. Research objectivesto determine antioxidant and anticancer activities of kombucha-based C. aeruginosa through in vitro and in silico study. Methodsproduction of kombucha-based C. aeruginosa with variation of C. aeruginosa extract concentration (2, 4, 6 %) and variation of time fermentation of kombucha production (6, 8, 10, 12, 14 and 16 days). Then antioxidant activity analysis was carried out with the DPPH assay. The bioactive compounds contained in kombucha-based C. aeruginosa was screened using LCHRMS (Liquid Chromatography-High Resolution Mas Spectrometry). Anticancer activity was predicted using in silico study such as PASS Online and molecular docking. ResultsThe highest antioxidant activity was showed by 6 % of C. aeruginosa and 14 days fermentation of kombucha (IC50 = 13.17). There were 15 bioactive compounds contained in kombucha-based C. aeruginosa and 4 of them with anticancer activity, such as 2-(8-Hydroxy-4a,8-dimethyldecahhydro-2-naphthalenyl)acrylic acid, 2-[(2-Chlorobenzyl)sulfanyl]-4,6-dimethylnicotinonitrile, 3,5-Di‑tert‑butyl‑4-hydroxybenzoic acid, and Zedoarondiol. 2-[(2-Chlorobenzyl)sulfanyl]-4,6-dimethylnicotinonitrile showed the most potential anticancer compound with the strongest interaction to inhibit ERa and PR protein.

Volatile organic compounds of the soil bacterium Bacillus halotolerans suppress pathogens and elicit defense-responsive genes in plants

Volatile organic compounds (VOCs) produced by bacteria play an important, yet relatively unexplored role in interactions between plants and phytopathogens. In this study, the soil bacterium Bacillus halotolerans NYG5 was identified as a potent biocontrol agent against several phytopathogenic fungi (Macrophomina phaseolina, Rhizoctonia solani, Pythium aphanidermatum, and Sclerotinia sclerotiorum) through the production of VOCs. NYG5-emitted VOCs also inhibited the growth of bacterial pathogens (Agrobacterium tumefaciens, Xanthomonas campestris, Clavibacter michiganensis, and Pseudomonas syringae). When cultured in various growth media, NYG5 produced a variety of VOCs. Five distinct VOCs (2-methylbutanoic acid, 5-methyl-2-hexanone, 2,3-hexanedione, 2-ethyl-1-hexanol, and 6-methyl-2-heptanone) were identified using headspace GC-MS. 2,3-Hexanedione exhibited potent lethal effects on the tested phytopathogens and nematicidal activity against Meloidogyne javanica at a concentration of 50 ppm. In addition, 0.05 ppm 2,3-hexanedione stimulated the expression of pathogenesis-related genes 1 and 2 in Arabidopsis thaliana. Interestingly, 2,3-hexanedione is used as a food additive at higher concentrations than those tested in this study. Hence, 2,3-hexanedione is a promising biologically active compound that might serve as a sustainable alternative to common chemical pesticides and an elicitor of plant defense.

Plant defensive responses to insect eggs are inducible by general egg-associated elicitors

Egg deposition by herbivorous insects is well known to elicit defensive plant responses. Our study aimed to elucidate the insect and plant species specificity of these responses. To study the insect species specificity, we treated Arabidopsis thaliana with egg extracts and egg-associated secretions of a sawfly (Diprion pini), a beetle (Xanthogaleruca luteola) and a butterfly (Pieris brassicae). All egg extracts elicited salicylic acid (SA) accumulation in the plant, and all secretions induced expression of plant genes known to be responsive to the butterfly eggs, among them Pathogenesis-Related (PR) genes. All secretions contained phosphatidylcholine derivatives, known elicitors of SA accumulation and PR gene expression in Arabidopsis. The sawfly egg extract did not induce plant camalexin levels, while the other extracts did. Our studies on the plant species specificity revealed that Solanum dulcamara and Ulmus minor responded with SA accumulation and cell death to P. brassicae eggs, i.e. responses also known for A. thaliana. However, the butterfly eggs induced neoplasms only in S. dulcamara. Our results provide evidence for general, phosphatidylcholine-based, egg-associated elicitors of plant responses and for conserved plant core responses to eggs, but also point to plant and insect species-specific traits in plant–insect egg interactions.

Genome-wide identification of rubber tree pathogenesis-related 10 (PR-10) proteins with biological relevance to plant defense

Pathogenesis-related 10 (PR-10) is a group of small intracellular proteins that is one of 17 subclasses of pathogenesis-related proteins in plants. The PR-10 proteins have been studied extensively and are well-recognized for their contribution to host defense against phytopathogens in several plant species. Interestingly, the accumulation of PR-10 proteins in the rubber tree, one of the most economically important crops worldwide, after being infected by pathogenic organisms has only recently been reported. In this study, the homologous proteins of the PR-10 family were systemically identified from the recently available rubber tree genomes in the NCBI database. The sequence compositions, structural characteristics, protein physical properties, and phylogenetic relationships of identified PR-10 proteins in rubber trees support their classification into subgroups, which mainly consist of Pru ar 1-like major allergens and major latex-like (MLP) proteins. The rubber tree PR10-encoding genes were majorly clustered on chromosome 15. The potential roles of rubber tree PR-10 proteins are discussed based on previous reports. The homologous proteins in the PR-10 family were identified in the recent genomes of rubber trees and were shown to be crucial in host responses to biotic challenges. The genome-wide identification conducted here will accelerate the future study of rubber tree PR-10 proteins. A better understanding of these defense-related proteins may contribute to alternative ways of developing rubber tree clones with desirable traits in the future.

Identification and Functional Analysis of PR Genes in Leaves from Variegated Tea Plant (Camellia sinensis)

Tea is a healthy beverage made from the leaves of the tea plant [Camellia sinensis (L.) O. Kuntze]. The tea plant is a perennial evergreen plant that is widely distributed in tropical and subtropical regions. PR proteins (pathogenesis-related proteins, PRs) are defense-related proteins induced under pathogenesis-related conditions. Currently, there are a few studies on PRs in plants. Tea leaf color mutants have been of wide interest to scientists as special materials. A tea plant displaying variegated spontaneous albinism found in a local tea plantation in Huangshan City, Anhui Province, China, was used as the material sample in this study. An analysis of preexisting transcriptomic and proteomic data revealed the significant upregulation of three classes of PRs. In order to investigate the correlation between PRs and variegated tea plants, a series of studies were conducted on PR genes. The results revealed the identification of 17 CsPR1, 3 CsPR4 and 31 CsPR5 genes in tea plants using bioinformatics methods, and their structures and promoter sequences. The expression of three PR1, two PR4 and one PR5 genes was determined to be induced in stress treatment experiments involving mechanical damage, insect bites, low temperature treatment, and fungal infections. Additionally, the ribonuclease activity of CsPR4 was successfully verified. This is the first study to report the ribonuclease activity of CsPR4 in tea plants. The results can serve as a reference for future studies on PRs in tea plants, offering new insights into information on albinism in tea plants.

OsMKK1 is a novel element that positively regulates the Xa21-mediated resistance response to Xanthomonas oryzae pv. oryzae in rice.

OsMKK1, a MAPK gene, positively regulates rice Xa21-mediated resistance response and also plays roles in normal growth and development process of rice. The mitogen-activated protein kinase (MAPK) cascade was highly conserved among eukaryotes, which played crucial roles in plant responses to pathogen infection. Bacterial blight is the most devastating bacterial disease. Xa21 confers broad-spectrum resistance to Xanthomonas oryzae pv. Oryzae (Xoo). This study identified that the transcription level of OsMKK1 was up-regulated in resistant response against Xoo, thus overexpression (OsMKK1-OX) and RNA interference (OsMKK1-RNAi) transgenic rice lines under the background of Xa21 was constructed. Compared with recipient control plants 4021, the OsMKK1-OX lines significantly enhanced disease resistance to Xoo, on the contrary, the resistance of OsMKK1-RNAi lines was weakened, demonstrated that OsMKK1 played a positive role in Xa21-mediated disease resistance pathway. A number of pathogenesis-related proteins, including PR1A, PR2 and PR10A showed enhanced expression in OsMKK1-OX lines, supported that these PR genes may be regulated by OsMKK1 to participate in the defense responses. In addition, the agronomic traits of OsMKK1 transgenic plants were affected. Overall, these results revealed the role of OsMKK1 in Xa21-mediated resistance against Xoo and in the normal growth and development process in rice.

Human lipocalins bind and export fatty acids through the secretory pathway of yeast cells.

The activation of fatty acids to their acyl-CoA derivatives is a crucial step for their integration into more complex lipids or their degradation via beta-oxidation. Yeast cells employ five distinct acyl-CoA synthases to facilitate this ATP-dependent activation of acyl chains. Notably, mutant cells that are deficient in two of these fatty acid-activating (FAA) enzymes, namely, Faa1 and Faa4, do not take up free fatty acids but rather export them out of the cell. This unique fatty acid export pathway depends on small, secreted pathogenesis-related yeast proteins (Pry). In this study, we investigate whether the expression of human fatty acid-binding proteins, including Albumin, fatty acid-binding protein 4 (Fabp4), and three distinct lipocalins (ApoD, Lcn1, and Obp2a), could promote fatty acid secretion in yeast. To optimize the expression and secretion of these proteins, we systematically examined various signal sequences in both low-copy and high-copy number plasmids. Our findings reveal that directing these fatty-acid binding proteins into the secretory pathway effectively promotes fatty acid secretion from a sensitized quadruple mutant model strain (faa1∆ faa4∆ pry1∆ pry3∆). Furthermore, the level of fatty acid secretion exhibited a positive correlation with the efficiency of protein secretion. Importantly, the expression of all human lipid-binding proteins rescued Pry-dependent fatty acid secretion, resulting in the secretion of both long-chain saturated and unsaturated fatty acids. These results not only affirm the in vitro binding capabilities of lipocalins to fatty acids but also present a novel avenue for enhancing the secretion of valuable lipidic compounds. Given the growing interest in utilizing yeast as a cellular factory for producing poorly soluble compounds and the potential of lipocalins as platforms for engineering substrate-binding specificity, our model is considered as a powerful tool for promoting the secretion of high-value lipid-based molecules.

Dual functionality of pathogenesis-related proteins: defensive role in plants versus immunosuppressive role in pathogens.

Plants respond to pathogen exposure by activating the expression of a group of defense-related proteins known as Pathogenesis-Related (PR) proteins, initially discovered in the 1970s. These PR proteins are categorized into 17 distinct families, denoted as PR1-PR17. Predominantly secreted, most of these proteins execute their defensive roles within the apoplastic space. Several PR proteins possess well-defined enzymatic functions, such as β-glucanase (PR2), chitinases (PR3, 4, 8, 11), proteinase (PR7), or RNase (PR10). Enhanced resistance against pathogens is observed upon PR protein overexpression, while their downregulation renders plants more susceptible to pathogen infections. Many of these proteins exhibit antimicrobial activity in vitro, and due to their compact size, some are classified as antimicrobial peptides. Recent research has unveiled that phytopathogens, including nematodes, fungi, and phytophthora, employ analogous proteins to bolster their virulence and suppress plant immunity. This raises a fundamental question: how can these conserved proteins act as antimicrobial agents when produced by the host plant but simultaneously suppress plant immunity when generated by the pathogen? In this hypothesis, we investigate PR proteins produced by pathogens, which we term "PR-like proteins," and explore potential mechanisms by which this class of virulence factors operate. Preliminary data suggests that these proteins may form complexes with the host's own PR proteins, thereby interfering with their defense-related functions. This analysis sheds light on the intriguing interplay between plant and pathogen-derived PR-like proteins, providing fresh insights into the intricate mechanisms governing plant-pathogen interactions.

Detection of Pathogenesis-Related (PR) Genes in Susceptible Tomato Plants Infected by Meloidogyne spp.

Meloidogyne species, as infective second-stage juveniles (J2s) larvae, are parasites able to attack host of relevant agronomic interest such as tomato plants. The identification of gene expression markers, useful to investigate the levels of root-knot nematode infection in the roots, is a fundamental tool in plant-pathogen interaction. The laboratory methods for analyzing the differential expression of pathogenesis-related (PR) genes constitute powerful tools for detecting the induced systemic acquired resistance defense response to M. incognita in infected plants and can be extended to all pathogen infection markers to obtain an early and sustainable control.

Differential induction of defense genes in hexaploid wheat roots by the plant-parasitic nematodes Pratylenchus neglectus and P. thornei.

Pratylenchus neglectus and P. thornei are among the most destructive root lesion nematodes of wheat in the Pacific Northwest, United States of America and throughout the world. The aim of this study was to determine whether both nematode species were similar in their ability to induce defense genes in roots of wheat genotype Scarlet, and whether a combination of both species induced a different pattern of gene induction than each species alone. The long-term aspect of the research was to identify nematode-inducible promoters for deploying defense genes in roots in breeding programs. The root transcriptomes of genotype Scarlet were obtained after a one-week infection period with each nematode species separately, or both species combined. Root defense gene expression was induced for all three treatments relative to the no-nematode control, but P. thornei affected expression to a greater extent compared to P. neglectus. The species combination induced the highest number of defense genes. This result was not predicted from nematode enumeration studies, in which P. thornei colonization was substantially lower than that of P. neglectus, and the nematode combination did not show a significant difference. Quantitative real time polymerase chain reaction (qRT-PCR) assays for Dehydrin2, Glucan endo-1,3-beta-glucosidase, 1-cys-Peroxiredoxin, Pathogenesis-related protein 1 and Late embryogenesis-abundant proteins 76 and group 3 authenticated the induction observed in the transcriptome data. In addition, a near-isogenic line of Scarlet harboring genetic resistance to fungal soilborne pathogens, called Scarlet-Rz1, showed similar or higher levels of defense gene expression compared to fungus-susceptible Scarlet in qRT-PCR assays. Finally, transcriptome expression patterns revealed nematode-inducible promoters that are responsive to both P. neglectus and P. thornei.

Harnessing chickpea bacterial endophytes for improved plant health and fitness.

Endophytic bacteria live asymptomatically inside the tissues of host plants without inflicting any damage. Endophytes can confer several beneficial traits to plants, which can contribute to their growth, development, and overall health. They have been found to stimulate plant growth by enhancing nutrient uptake and availability. They can produce plant growth-promoting substances such as auxins, cytokinins, and gibberellins, which regulate various aspects of plant growth and development. Endophytes can also improve root system architecture, leading to increased nutrient and water absorption. Some endophytes possess the ability to solubilize nutrients, such as phosphorus and potassium, making them more available for plant uptake, and fixing atmospheric nitrogen. Chickpea (Cicer arietinum) is a major legume crop that has mutualistic interactions with endophytes. These endophytes can benefit the chickpea plant in various ways, including higher growth, improved nutrient uptake, increased tolerance to abiotic and biotic stressors, and disease suppression. They can produce enzymes and metabolites that scavenge harmful reactive oxygen species, thus reducing oxidative stress. Moreover, several studies reported that endophytes produce antimicrobial compounds, lytic enzymes, and volatile organic compounds that inhibit the growth of fungal pathogens and trigger systemic defense responses in plants, leading to increased resistance against a broad range of pathogens. They can activate plant defense pathways, including the production of defense-related enzymes, phytoalexins, and pathogenesis-related proteins, thereby providing long-lasting protection. It is important to note that the diversity and function of chickpea-associated endophytes can vary depending on factors such as variety, geographical location, and environmental conditions. The mechanisms behind the plant-beneficial interactions are still being intensively explored. In this review, new biotechnologies in agricultural production and ecosystem stability were presented. Thus, harnessing chickpea endophytes could be exploited in developing drought-resistant cultivars that can maintain productivity in arid and semi-arid environments, crucial for meeting the global demand for chickpeas.

Studies on biochemical changes and expression of Pathogenesis-Related proteins (PR Proteins) associated with plant defense mechanism induced by Arbuscular Mycorhizal Fungus Rhizophagus intraradices against Meloidogyne incognita

Studies on biochemical changes and expression of Pathogenesis-Related proteins (PR Proteins) associated with plant defense mechanism induced by Arbuscular Mycorhizal Fungus Rhizophagus intraradices against Meloidogyne incognita

Tomato R-gene-mediated resistance against Fusarium wilt originates in roots and extends to shoots via xylem to limit pathogen colonization.

Vascular wilt disease, caused by the soil-borne fungus Fusarium oxysporum (Fo), poses a threat to many crop species. Four different tomato resistance (R) genes (I-1, I-2, I-3, and I-7) have been identified to confer protection against Fo f.sp. lycopersici (Fol). These I genes are root-expressed and mount an immune response upon perception of the invading fungus. Despite immune activation, Fol is still able to colonize the xylem vessels of resistant tomato lines. Yet, the fungus remains localized in the vessels and does not colonize adjacent tissues or cause disease. The molecular mechanism constraining Fol in the vascular system of the stem remains unclear. We here demonstrate that an I-2-resistant rootstock protects a susceptible scion from Fusarium wilt, notwithstanding fungal colonization of the susceptible scion. Proteomic analyses revealed the presence of fungal effectors in the xylem sap of infected plants, showing that the lack of fungal pathogenicity is not due to its inability to express its virulence genes. To identify mobile root-derived proteins, potentially involved in controlling fungal proliferation, comparative xylem sap proteomics was performed. We identified distinct pathogenesis-related (PR) protein profiles in xylem sap from Fol-inoculated I-1, I-2, I-3, and I-7 resistant lines. Despite structural diversity, all four immune receptors trigger the accumulation of a common set of four PR proteins: PR-5x, PR-P2, and two glucan endo-1,3-β-D-glucosidases. This research provides insights into Fusarium resistance mechanisms and identifies a core set of proteins whose abundance correlates with defense against Fusarium wilt.

Gamma-aminobutyric acid treatment promotes resistance against Sogatella furcifera in rice.

The Sogatella furcifera (Horváth) (Homoptera: Delphacidae) is a white-backed planthopper (WBPH) that causes "hopper burn" in rice, resulting in severe yield loss. Gamma-aminobutyric acid (GABA) is a well-known neurotransmitter that inhibits neurotransmission in insects by binding to specific receptors. In this study, we investigated the potential role of GABA in modulating rice resistance to WBPH and evaluated possible defense mechanisms. The experiment was conducted in green house in pots consist of four groups: control, GABA-treated, WBPH-infested, and WBPH-infested treated with GABA. Among the various tested concentration of GABA, 15 mM GABA was applied as a single treatment in water. The treatment was administered one week before WBPH infestation. The results revealed that 15 mM GABA treatment strongly increased WBPH resistance. A plate-based assay indicated that direct application of 15 mM GABA increased the mortality rate of WBPH and increased the damage recovery rate in rice plants. We found that GABA treatment increased the activation of antioxidant enzymes and reduced the reactive oxygen species content and malondialdehyde contents, and reduced the damage rate caused by WBPH. Interestingly, GABA-supplemented plants infested with WBPH exhibited increased phenylalanine ammonia-lyase and pathogenesis-related (PR) genes expression levels. GABA induced the accumulation of abscisic acid (ABA) and salicylic acid (SA) and enhanced the stomata closure and reduced leaf vessels to reduce water conductance during WBPH stress. Furthermore, we found that GABA application to the plant induced the expression of Jasmonic acid (JA) biosynthesis genes (LOX, AOS, AOC, and OPR) and melatonin biosynthesis-related genes (TDC, T5H, ASMT, and SNAT). Our study suggested that GABA increases resistance against WBPH infestation by regulating antioxidant defense system, TCA cycle regulation, phytohormonal signaling, and PR gene regulation.

Preparation of Joint Extracts.

Since mice are widely used to establish rheumatoid arthritis models, assessment of the pathogenesis of local arthritis is fundamental. Proteins are the most diverse group of biologically important molecules and are essential for cellular structure and function. The first step in pathogenesis-related protein analysis is joint tissue extraction. Unlike other large rodents, obtaining synovium from model mice is challenging since it is so small and fragile. In this chapter, methods for harvesting synovium through a quadriceps approach and preparing protein extracts are introduced.

Oral allergy syndrome (OAS)

The pollen-food allergy syndrome, also known as oral allergy syndrome, is characterized by local reactions in the mouth and throat after consuming certain raw plant foods in individuals sensitized to pollen from grass, weeds, and trees. Birch-apple is the prototype of this syndrome, with apple, pear, and plum being the most commonly associated foods. Symptoms are usually limited to the oral cavity but can include systemic reactions, including anaphylaxis. Sensitization to pollen allergens, such as lipid transfer proteins, profilin, and PR-10 proteins, triggers this syndrome. Its prevalence varies by geographic region and the predominant pollen type, affecting between 30% and 60% of food allergies. Diagnosis involves a clinical history, skin tests, and, in ambiguous cases, double-blind, placebo-controlled oral food challenges. Treatment primarily involves avoiding trigger foods.

Rice transcription factor OsNAC2 maintains the homeostasis of immune responses to bacterial blight.

Rice (Oryza sativa) bacterial blight, caused by Xanthomonas oryzae pv. Oryzae (Xoo), threatens plant growth and yield. However, the molecular mechanisms underlying rice immunity against Xoo remain elusive. Here, we identified a NAC (NAM-ATAF-CUC) transcription factor OsNAC2 as a negative regulator in the resistance to bacterial blight disease in rice. Constitutive overexpression of OsNAC2 inhibited the expression of salicylic acid (SA) biosynthesis-related genes (i.e. isochorismate synthase 1 (OsICS1), phenylalanine ammonia lyase 3 (OsPAL3), etc.) with adverse impacts on the pathogenesis-related proteins (PRs) responses and compromised blight resistance. Moreover, OsNAC2 interacted with APETALA2/ethylene-responsive element binding protein (AP2/EREBP) transcription factor OsEREBP1 and possibly threatened its protein stability, destroying the favorable interaction of OsEREBP1-Xa21-binding protein OsXb22a in the cytoplasm during Xoo-induced infection. On the contrary, downregulation of OsNAC2 resulted in enhanced resistance to bacterial blight in rice without any growth or yield penalties. Our results demonstrated that OsNAC2 inhibits SA signaling and stably interacted with OsEREBP1 to impair disease resistance. This OsNAC2-OsEREBP1-based homeostatic mechanism provided insights into the competition between rice and bacterial pathogens, and it will be useful to improve the disease resistance of important crops through breeding.

Effects of Enhanced Resistance and Transcriptome Analysis of Twig Blight Disease by Exogenous Brassinolide in Myrica rubra.

Twig blight disease is the primary disease that affects the production of Myrica rubra in China. It was reported that exogenous brassinolide (BL) can improve disease resistance in plants. Here, we examined the effects of exogenous BL on disease resistance, chlorophyll contents, antioxidant enzyme activity, ROS accumulation, and key gene expression of M. rubra to analyze the mechanism of BR-induced resistance of twig blight disease in M. rubra. The results demonstrated that 2.0 mg·L-1 of BL could significantly lessen the severity of twig blight disease in M. rubra. Exogenous BL increased the contents of chlorophyll a, chlorophyll b, carotenoids, and total chlorophyll. Moreover, exogenous BL also significantly enhanced the activity of antioxidant enzymes such as superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), and decreased malondialdehyde (MDA) content and reactive oxygen species (ROS) accumulation in leaves, such as H2O2 and O2·-. Additionally, exogenous BL dramatically up-regulated the expression of pathogenesis-related (PR) genes such as MrPR1, MrPR2, and MrPR10, as well as important genes such as MrBAK1, MrBRI1, and MrBZR1 involved in brassinosteroid (BR) signaling pathway. The transcriptome analysis revealed that a total of 730 common differentially expressed genes (DEGs) under BL treatment were found, and these DEGs were primarily enriched in four Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. Based on these findings, nine important candidate genes related to the resistance of twig blight disease under BL treatment were further identified. In this study, we elucidated the effects of exogenous BL on enhancing the resistance of M. rubra to twig blight disease and preliminary analyzed the potential mechanism of resistance induction, which will provide a crucial foundation for the management and prevention of twig blight disease in M. rubra.