An Acidic PATHOGENESIS-RELATED1 Gene of Oryza grandiglumis is Involved in Disease Resistance Response Against Bacterial Infection

Identification of CAP genes in finger lime (Citrus australasica) and their role in plant responses to abiotic and biotic stress

The study focuses on the in silico analysis of cysteine-rich secretory proteins and PR1-like (CAP) genes in finger lime (Citrus australasica), a citrus species known for its tolerance to Huanglongbing (HLB). We identified several PR1-like genes, all belonging to the CRISP family within the CAP superfamily. Of them, CaCAP2 transcript levels increased by over 300-fold in the finger lime compared to 'Valencia' sweet orange upon infection with 'Candidatus Liberibacter asiaticus' (CaLas). Localization studies using an EGFP fusion showed that the CAP2 protein is predominantly located in the nucleus, extracellular and plasma membrane. The study also examined CAP2 transcript levels in response to cold, drought stress, and salicylic acid application. Despite environmental stress causing apparent damage, CAP genes seem to play a significant role in managing both biotic and abiotic stresses. Analysis of CAP2 gene promoters from finger lime and sweet orange revealed 95.33% sequence identity, with variations in transcription factor-binding sites and cis-acting elements such as Stress Response Element (STRE: AGGGG), which might influence the differential expression of CAP2 between the two species. Additionally, expressing the finger lime-derived CaCAP2 gene in transgenic Nicotiana tabacum induced a strong defense response against Pseudomonas syringae pv. Tabaci., underscoring the CAP gene's crucial role in plant defense mechanisms against bacterial pathogens.

Zucchini yellow mosaic virus-induced hypersensitive response is associated with pathogenesis-related 1 protein expression and confers resistance in watermelon

KEY MESSAGE

The pathogenesis-related 1 gene of watermelon responds to the infection of ZYMV and contributes to the resistance of its host. Zucchini yellow mosaic virus (ZYMV; family Potyviridae) is a single-stranded positive-sense RNA virus that is a serious threat to cucurbits. Previously, we observed a hypersensitivity response (HR) in the systemic leaves of the 938-16-B watermelon line infected with ZYMV, distinct from the typical HR at infected sites. In this study, we confirmed that ZYMV accumulation in 938-16-B was significantly lower than in the susceptible line H1. Upon inoculation, the entry of ZYMV-eGFP into mesophyll cells is restricted into necrotic spots in leaves, indicating that resistance to ZYMV in 938-16-B is linked to the HR. Further, grafting experiments between 938-16-B and susceptible varieties were performed, and revealed an HR induction in susceptible varieties, suggesting the transfer of resistance signal(s) from 938-16-B to susceptible varieties. Through RNA-sequencing and proteomics analyses of the H1 scions on 938-16-B rootstock, a pathogenesis-related 1 (ClPR1) gene was identified. Specifically, ClPR1 expression is unique to ZYMV-infected 938-16-B. Repression of the expression of ClPR1 prevents an HR in 938-16-B. Conversely, overexpression of ClPR1 in susceptible varieties significantly reduces ZYMV accumulation, but an HR was not induced in susceptible line. Besides the virus, jasmonic acid (JA) can also trigger an HR in 938-16-B. Intriguingly, the expression of ClPR1 (Cla97C02G034020) is induced in both of 938-16-B and H1 by MeJA, rather than salicylic acid. These results suggest that HR is associated with the expression of ClPR1 and contributes to resistance to ZYMV in 938-16-B.

Pull the fuzes: Processing protein precursors to generate apoplastic danger signals for triggering plant immunity

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

A pathogenesis-related protein 1 of Cucurbita moschata responds to powdery mildew infection

Pumpkin (Cucurbita moschata Duch.) productivity is severely hindered by powdery mildew (PM) worldwide. The causative agent of pumpkin PM is Podosphaera xanthii, a biotrophic fungus. Pathogenesis-related protein 1 (PR1) homolog was previously identified from transcriptomic analysis of a PM-resistant pumpkin. Here, we investigated the effects of CmPR1 gene from pumpkin for resistance to PM. Subcellular localization assay revealed that CmPR1 is a cytoplasmic protein in plants. The expression of CmPR1 gene was strongly induced by P. xanthii inoculation at 48 h and exogenous ethylene (ET), jasmonic acid (JA) and NaCl treatments, but repressed by H2O2 and salicylic acid (SA) treatments. Visual disease symptoms, histological observations of fungal growth and host cell death, and accumulation of H2O2 in transgenic tobacco plants indicated that CmPR1 overexpression significantly enhanced the resistance to Golovinomyces cichoracearum compared to wild type plants during PM pathogens infection, possibly due to inducing cell death and H2O2 accumulation near infected sites. The expression of PR1a was significantly induced in transgenic tobacco plants in response to G. cichoracearum, suggesting that CmPR1 overexpression positively modulates the resistance to PM via the SA signaling pathway. These findings indicate that CmPR1 is a defense response gene in C. moschata and can be exploited to develop disease-resistant crop varieties.

The function of plant PR1 and other members of the CAP protein superfamily in plant-pathogen interactions

The pathogenesis-related (PR) proteins of plants have originally been identified as proteins that are strongly induced upon biotic and abiotic stress. These proteins fall into 17 distinct classes (PR1-PR17). The mode of action of most of these PR proteins has been well characterized, except for PR1, which belongs to a widespread superfamily of proteins that share a common CAP domain. Proteins of this family are not only expressed in plants but also in humans and in many different pathogens, including phytopathogenic nematodes and fungi. These proteins are associated with a diverse range of physiological functions. However, their precise mode of action has remained elusive. The importance of these proteins in immune defence is illustrated by the fact that PR1 overexpression in plants results in increased resistance against pathogens. However, PR1-like CAP proteins are also produced by pathogens and deletion of these genes results in reduced virulence, suggesting that CAP proteins can exert both defensive and offensive functions. Recent progress has revealed that plant PR1 is proteolytically cleaved to release a C-terminal CAPE1 peptide, which is sufficient to activate an immune response. The release of this signalling peptide is blocked by pathogenic effectors to evade immune defence. Moreover, plant PR1 forms complexes with other PR family members, including PR5, also known as thaumatin, and PR14, a lipid transfer protein, to enhance the host's immune response. Here, we discuss possible functions of PR1 proteins and their interactors, particularly in light of the fact that these proteins can bind lipids, which have important immune signalling functions.

Genome-Wide Identification and Expression Profiling of Pathogenesis-Related Protein 1 (PR-1) Genes in Durum Wheat (Triticum durum Desf.)

Pathogen-related proteins (PRs) are diversified proteins with a low molecular weight implicated in plant response to biotic and abiotic stress as well in regulating different functions in plant maturation. Interestingly, no systematical study has been conducted in durum wheat (Triticum turgidum subsp. durum). In the present study, 12 PR-1 genes encoding a CAP superfamily domain were identified in the genome of Triticum turgidum subsp. durum, which is an important cereal, using in silico approaches. Additionally, phylogenetic analysis showed that the PR-1 genes were classified into three groups based on their isoelectric point and the conserved motif domain. Moreover, our analysis showed that most of the TdPR-1 proteins presented an N-terminal signal peptide. Expression patterns analysis showed that the PR-1 gene family presented temporal and spatial specificity and was induced by different abiotic stresses. This is the first report describing the genome-scale analysis of the durum wheat PR-1 gene family, and these data will help further study the roles of PR-1 genes during stress responses, leading to crop improvement.

Isolation and characterization of a pathogenesis-related protein 1 (SlPR1) gene with induced expression in tomato (Solanum lycopersicum) during Ralstonia solanacearum infection

In order to explore the function of pathogenesis-related (PR) proteins in regulating tomato (Solanum lycopersicum) biological stress response, a PR protein gene (SlPR1) (Gen ID: Solyc01g106620.2) was isolated from tomato by RT-PCR. The full-length cDNA was 760 bp, which encoded a total of 179 amino acids. The cDNA contained a 42 bp 5' non-coding region, a 178 bp 3' non-coding region, and an open reading frame (ORF) of 540 bp. Homologous sequence alignment and phylogenetic analysis indicated that SlPR1 was highly homologous with a S. tuberosum PR1 protein, followed by S. pennellii. The predicted molecular weight of SlPR1 was 20,123.47 Da, the isoelectric point was 8.48, and the protein was found to be a secreted protein with a transmembrane structure. Quantitative real-time PCR (qRT-PCR) revealed that SlPR1 gene expression was highest in tomato stems, and could be induced by infection with Ralstonia solanacearum, and treatment with salicylic acid (SA) and methyl jasmonate acid (MeJA).Virus-induced gene silencing (VIGS) of SlPR1 decreased plant resistance to bacterial wilt, suggesting that SlPR1 positively regulates tomato resistance to this disease.This study provides a reference for the further exploration of the role of SlPR1 in the response of tomato to bacterial wilt and other stressors.

Exploring the Role of Salicylic Acid in Regulating the Colonization Ability of Bacillus subtilis 26D in Potato Plants and Defense against Phytophthora infestans

Plant colonization by endophytic bacteria is mediated by different biomolecules that cause dynamic changes in gene expression of both bacteria and plant. Phytohormones, in particular, salicylic acid, play a key role in the regulation of endophytic colonization and diversity of bacteria in methaphytobiome. For the first time it was found that salicylic acid influenced motility in biofilms and transcription of the surfactin synthetase gene of the endophytic strain Bacillus subtilis 26D in vitro. Treatment of Solanum tuberosum plants with salicylic acid, along with B. subtilis 26D, increased the number of endophytic cells of bacteria in potato internal tissues and level of transcripts of bacterial surfactin synthetase gene and decreased transcription of plant PR genes on the stage of colonisation with endophytes. Thus, the production of surfactin plays an important role in endophytic colonization of plants, and salicylic acid has an ability to influence this mechanism. Here we firstly show that plants treated with salicylic acid and B. subtilis 26D showed enhanced resistance to the late blight pathogen Phytophthora infestans, which was accompanied by increase in transcriptional activity of plant PR-genes and bacterial surfactin synthetase gene after pathogen inoculation. Therefore, it is suggested that salicylic acid can modulate physiological status of the whole plant–endophyte system and improve biocontrol potential of endophytic strains.

Transcriptomics and iTRAQ-proteomics analyses provide novel insights into the defense mechanism of black shank disease in tobacco

Black shank disease caused by Phytophthora nicotianae is one of the most important diseases in tobacco worldwide and can result in a devastating loss in tobacco cultivation. Many efforts have been carried out to identify the chromosome segment from Nicotiana plumbaginifolia containing a resistance locus carrying a gene named Php; however, the Php gene has not been cloned, and knowledge of the potential mechanism of the Php gene in the resistant lines is limited. To further characterize the resistance mechanism of the Php gene, we first used the resistant line "RBST" and the susceptible cultivar "Honghuadajinyuan" (HD) to obtain the near-isogenic line RBS89 containing the Php gene from RBST. RBS89 showed high resistance to black shank disease. Transcriptomic and iTRAQ analyses were applied to explore the potential defense mechanisms in RBS89 plants in comparison with HD plants with or without inoculation. Many differentially expressed genes (DEGs) and proteins were identified, and some pathogenesis-related (PR) proteins were extensively abundant in the RBS89 plants when compared with the HD plants in response to black shank disease. Importantly, overexpression of the PR gene NtPR-1B in HD plants improved the resistance of tobacco plants to black shank disease, indicating that NtPR-1B and Php genes might have similar roles in protecting tobacco from black shank disease. However, the relationship between NtPR-1B and Php genes requires further analysis. Therefore, our study provides valuable information for breeding tobacco cultivars with black shank disease resistance and sheds light on the defense mechanism of black shank disease in tobacco for enhancing Phytophthora resistance in other Solanaceae crops.

Isolation and Characterization of a Novel Pathogenesis-Related Protein-1 Gene (AvPR-1) with Induced Expression in Oat (Avena sativa L.) during Abiotic and Hormonal Stresses

Pathogenesis-related protein-1 (PR-1) plays crucial roles in regulating plant responses to biotic and abiotic stresses. This study aimed to isolate and characterize the first PR-1 (AvPR-1) gene in oat (Avena sativa L.). AvPR-1 presented conserved signal peptide motifs and core amino acid composition in the functional protein domains as the protein sequence of AvPR-1 presented 98.28%, 97.7%, and 95.4% identity with known PR1 proteins isolated from Triticum aestivum PRB1-2-like, Triticum dicoccoides PRB1-2-like, and Aegilops tauschii subsp. tauschii, respectively. Bioinformatic analysis showed that the AvPR-1 protein belongs to the CAP superfamily (PF00188). Secondary and 3D structure analyses of the AvPR-1 protein were also conducted, confirming sequence conservation of PR-1 among studied species. The AvPR-1 protein harbors a calmodulin-binding domain located in its C-terminal part as previously shown for its wheat homolog TdPR1.2. Moreover, gene expression analysis showed that AvPR-1 was induced in response to many abiotic and hormonal stresses especially in leaves after treatment for 48 h. This is the first study exhibiting the expression profiles of the AvPR-1 gene under different stresses in oat.

Genome-wide analysis of pathogenesis-related protein 1 (PR-1) gene family from Musa spp. and its role in defense response during stresses

Pathogenesis related protein-1 (PR-1) is the most abundantly produced protein during defense response against many biotic and abiotic stresses. However, knowledge on PR-1 gene family and its evolutionary relationship in banana is very limited. In order to study the potential role of PR-1 genes in banana, genome wide identification, structure analysis and expressions were performed. A total of 15 and 11 PR-1 genes were identified from A and B genomes of banana and the proteins encoded by this gene family are of varying lengths and harbor conserved domains and motifs. PR-1 genes are unevenly dispersed on 11 chromosomes with segmental duplication in both A and B genome, suggesting an important contribution of duplication in expansion of PR-1 gene family in banana. qRT-PCR analysis of PR-1 gene showed positive correlation with the RNAseq data under various stresses and examination of expression pattern of selected MaPR-1 genes in banana revealed its role in biotic and abiotic stresses in general and fusarium wilt in particular. This study provides significant insight into the functions of PR-1 genes which can be further exploited as a promising candidate for developing multiple stress tolerant banana varieties.

Pathogenesis-related protein 1 (PR-1) genes in soybean: Genome-wide identification, structural analysis and expression profiling under multiple biotic and abiotic stresses

Plant pathogenesis-related (PR) proteins are a large group of proteins, classified in 17 families, that are induced by pathological conditions. Here, we characterized the soybean PR-1 (GmPR-1) gene repertoire at the sequence, structural and expression levels. We found 24 GmPR-1 genes, clustered in two phylogenetic groups. GmPR-1 genes are under strong purifying selection, particularly those that emerged by tandem duplications. GmPR-1 promoter regions are abundant in cis-regulatory elements associated with major stress-related transcription factor families, namely WRKY, ERF, HD-Zip, C2H2, NAC, and GATA. We observed that 23 GmPR-1 genes are induced by stress conditions or exclusively expressed upon stress. We explored 1972 transcriptome samples, including 26 stress conditions, revealing that most GmPR-1 genes are differentially expressed in a plethora of biotic and abiotic stresses. Our findings highlight stress-responsive GmPR-1 genes with potential biotechnological applications, such as the development of transgenic lines with increased resistance to biotic and abiotic stresses.

Pathogenesis-related protein 1 (PR-1) genes in soybean: Genome-wide identification, structural analysis and expression profiling under multiple biotic and abiotic stresses

Plant pathogenesis-related (PR) proteins are a large group of proteins, classified in 17 families, that are induced by pathological conditions. Here, we characterized the soybean PR-1 (GmPR-1) gene repertoire at the sequence, structural and expression levels. We found 24 GmPR-1 genes, clustered in two phylogenetic groups. GmPR-1 genes are under strong purifying selection, particularly those that emerged by tandem duplications. GmPR-1 promoter regions are abundant in cis-regulatory elements associated with major stress-related transcription factor families, namely WRKY, ERF, HD-Zip, C2H2, NAC, and GATA. We observed that 23 GmPR-1 genes are induced by stress conditions or exclusively expressed upon stress. We explored 1972 transcriptome samples, including 26 stress conditions, revealing that most GmPR-1 genes are differentially expressed in a plethora of biotic and abiotic stresses. Our findings highlight stress-responsive GmPR-1 genes with potential biotechnological applications, such as the development of transgenic lines with increased resistance to biotic and abiotic stresses.

Expression profiling of pathogenesis-related Protein-1 (PR-1) genes from Solanum tuberosum reveals its critical role in phytophthora infestans infection

Pathogen-related (PR) proteins are an integral part of plants' defense mechanisms against various types of biotic and abiotic stresses. A little is known about the importance of these PR proteins in potato defense mechanisms. In the current study, a total of 22 pathogenesis-related 1 genes were identified in the potato genome. All identified proteins possessed the CAP superfamily domain with some other motifs. The cis-acting elements analysis identified several stress-responsive elements, including MYB, ABRE, and MeJRE. The gene duplication events demonstrated purifying and positive selection pressure. Expression profiling showed high transcripts level in root compared to other tissues; however, some genes have tissue-specific expression. Furthermore, the PR-1-5 gene is transcriptionally induced under Phytophthora infestans stress and hormonal (ABA and IAA) treatments. The Real-Time qPCR analysis also validated the RNA-seq data results of genes with maximum expression in roots compared to leaves and stems. The current study results provided basic data for functional characterization and can also use as a reference study for other important crops.

A Genome-Wide Analysis of Pathogenesis-Related Protein-1 (PR-1) Genes from Piper nigrum Reveals Its Critical Role during Phytophthora capsici Infection

Black pepper (Piper nigrum L.) is a prominent spice that is an indispensable ingredient in cuisine and traditional medicine. Phytophthora capsici, the causative agent of footrot disease, causes a drastic constraint in P. nigrum cultivation and productivity. To counterattack various biotic and abiotic stresses, plants employ a broad array of mechanisms that includes the accumulation of pathogenesis-related (PR) proteins. Through a genome-wide survey, eleven PR-1 genes that belong to a CAP superfamily protein with a caveolin-binding motif (CBM) and a CAP-derived peptide (CAPE) were identified from P. nigrum. Despite the critical functional domains, PnPR-1 homologs differ in their signal peptide motifs and core amino acid composition in the functional protein domains. The conserved motifs of PnPR-1 proteins were identified using MEME. Most of the PnPR-1 proteins were basic in nature. Secondary and 3D structure analyses of the PnPR-1 proteins were also predicted, which may be linked to a functional role in P. nigrum. The GO and KEGG functional annotations predicted their function in the defense responses of plant-pathogen interactions. Furthermore, a transcriptome-assisted FPKM analysis revealed PnPR-1 genes mapped to the P. nigrum-P. capsici interaction pathway. An altered expression pattern was detected for PnPR-1 transcripts among which a significant upregulation was noted for basic PnPR-1 genes such as CL10113.C1 and Unigene17664. The drastic variation in the transcript levels of CL10113.C1 was further validated through qRT-PCR and it showed a significant upregulation in infected leaf samples compared with the control. A subsequent analysis revealed the structural details, phylogenetic relationships, conserved sequence motifs and critical cis-regulatory elements of PnPR-1 genes. This is the first genome-wide study that identified the role of PR-1 genes during P. nigrum-P. capsici interactions. The detailed in silico experimental analysis revealed the vital role of PnPR-1 genes in regulating the first layer of defense towards a P. capsici infection in Panniyur-1 plants.

Overexpression of a plasma membrane protein generated broad-spectrum immunity in soybean

Plants fight-off pathogens and pests by manifesting an array of defence responses using their innate immunity mechanisms. Here we report the identification of a novel soybean gene encoding a plasma membrane protein, transcription of which is suppressed following infection with the fungal pathogen, Fusarium virguliforme. Overexpression of the protein led to enhanced resistance against not only against F. virguliforme, but also against spider mites (Tetranychus urticae, Koch), soybean aphids (Aphis glycines, Matsumura) and soybean cyst nematode (Heterodera glycines). We, therefore, name this protein as Glycine max disease resistance 1 (GmDR1; Glyma.10g094800). The homologues of GmDR1 have been detected only in legumes, cocoa, jute and cotton. The deduced GmDR1 protein contains 73 amino acids. GmDR1 is predicted to contain an ecto- and two transmembrane domains. Transient expression of the green fluorescent protein fused GmDR1 protein in soybean leaves showed that it is a plasma membrane protein. We investigated if chitin, a pathogen-associated molecular pattern (PAMP), common to all pathogen and pests considered in this study, can significantly enhance defence pathways among the GmDR1-overexpressed transgenic soybean lines. Chitin induces marker genes of the salicylic- and jasmonic acid-mediated defence pathways, but suppresses the defence pathway regulated by ethylene. Chitin induced SA- and JA-regulated defence pathways may be one of the mechanisms involved in generating broad-spectrum resistance among the GmDR1-overexpressed transgenic soybean lines against two serious pathogens and two pests including spider mites, against which no known resistance genes have been identified in soybean and among the most other crop species.

SUPPRESSOR OF GAMMA RESPONSE 1 acts as a regulator coordinating crosstalk between DNA damage response and immune response in Arabidopsis thaliana

Plants live in constantly changing and often unfavorable or stressful environments. Environmental changes induce biotic and abiotic stress, which, in turn, may cause genomic DNA damage. Hence, plants simultaneously suffer abiotic/biotic stress and DNA damage. However, little information is available on the signaling crosstalk that occurs between DNA damage and abiotic/biotic stresses. Arabidopsis thaliana SUPPRESSOR OF GAMMA RESPONSE1 (SOG1) is a pivotal transcription factor that regulates thousands of genes in response to DNA double-strand break (DSB), and we recently reported that SOG1 has a role in immune responses. In the present study, the effects of SOG1 overexpression on the DNA damage and immune responses were examined. Results found that SOG1 overexpression enhances the regulation of numerous downstream genes. Relative to the wild type plants, then, DNA damage responses were observed to be strongly induced. SOG1 overexpression also upregulates chitin (a major components of fungal cell walls) responsive genes in the presence of DSBs, implying that pathogen defense response is activated by DNA damage via SOG1. Further, SOG1 overexpression enhances fungal resistance. These results suggest that SOG1 regulates crosstalk between DNA damage response and the immune response and that plants have evolved a sophisticated defense network to contend with environmental stress.

Modahl C, Maenaka K, Aoki-Shioi N. Cysteine-Rich Secretory Proteins (CRISPs) From Venomous Snakes: An Overview of the Functional Diversity in A Large and Underappreciated Superfamily

The CAP protein superfamily (Cysteine-rich secretory proteins (CRISPs), Antigen 5 (Ag5), and Pathogenesis-related 1 (PR-1) proteins) is widely distributed, but for toxinologists, snake venom CRISPs are the most familiar members. Although CRISPs are found in the majority of venoms, very few of these proteins have been functionally characterized, but those that have been exhibit diverse activities. Snake venom CRISPs (svCRISPs) inhibit ion channels and the growth of new blood vessels (angiogenesis). They also increase vascular permeability and promote inflammatory responses (leukocyte and neutrophil infiltration). Interestingly, CRISPs in lamprey buccal gland secretions also manifest some of these activities, suggesting an evolutionarily conserved function. As we strive to better understand the functions that CRISPs serve in venoms, it is worth considering the broad range of CRISP physiological activities throughout the animal kingdom. In this review, we summarize those activities, known crystal structures and sequence alignments, and we discuss predicted functional sites. CRISPs may not be lethal or major components of venoms, but given their almost ubiquitous occurrence in venoms and the accelerated evolution of svCRISP genes, these venom proteins are likely to have functions worth investigating.

The mitogen activated protein kinase (MAPK) gene family functions as a cohort during the Glycine max defense response to Heterodera glycines

Mitogen activated protein kinases (MAPKs) play important signal transduction roles. However, little is known regarding how they influence the gene expression of other family members and the relationship to a biological process, including the Glycine max defense response to Heterodera glycines. Transcriptomics have identified MAPK gene expression occurring within root cells undergoing a defense response to a pathogenic event initiated by H. glycines in the allotetraploid Glycine max. Functional analyses are presented for its 32 MAPKs revealing 9 have a defense role, including homologs of Arabidopsis thaliana MAPK (MPK) MPK2, MPK3, MPK4, MPK5, MPK6, MPK13, MPK16 and MPK20. Defense signaling occurring through pathogen activated molecular pattern (PAMP) triggered immunity (PTI) and effector triggered immunity (ETI) have been determined in relation to these MAPKs. Five different types of gene expression relate to MAPK expression, influencing PTI and ETI gene expression and proven defense genes including an ABC-G transporter, 20S membrane fusion particle components, glycoside biosynthesis, carbon metabolism, hemicellulose modification, transcription and secretion. The experiments show MAPKs broadly influence defense MAPK gene expression, including the co-regulation of parologous MAPKs and reveal its relationship to proven defense genes. The experiments reveal each defense MAPK induces the expression of a G. max homolog of a PATHOGENESIS RELATED1 (PR1), itself shown to function in defense in the studied pathosystem.

NtPR1a regulates resistance to Ralstonia solanacearum in Nicotiana tabacum via activating the defense-related genes

Pathogenesis-related proteins (PRs) are associated with the development of systemic acquired resistance (SAR) against further infection enforced by fungi, bacteria and viruses. PR1a is the first PR-1 member that could be purified and characterized. Previous studies have reported its role in plants' resistance system against oomycete pathogens. However, the role of PR1a in Solanaceae plants against the bacterial wilt pathogen Ralstonia solanacearum remains unclear. To assess roles of NtPR1a in tobacco responding to R. solanacearum, we performed overexpression experiments in Yunyan 87 plants (a susceptible tobacco cultivar). The results illuminated that overexpression of NtPR1a contributed to improving resistance to R. solanacearum in tobacco Yunyan 87. Specifically speaking, NtPR1a gene could be induced by exogenous hormones like salicylic acid (SA) and pathogenic bacteria R. Solanacearum. Moreover, NtPR1a-overexpressing tobacco significantly reduced multiple of R. solanacearum and inhibited the development of disease symptoms compared with wild-type plants. Importantly, overexpression of NtPR1a activated a series of defense-related genes expression, including the hypersensitive response (HR)-associated genes NtHSR201 and NtHIN1, SA-, JA- and ET-associated genes NtPR2, NtCHN50, NtPR1b, NtEFE26, and Ntacc oxidase, and detoxification-associated gene NtGST1. In summary, our results suggested that NtPR1a-enhanced tobacco resistance to R. solanacearum may be mainly dependent on activation of the defense-related genes.

Harpin-inducible defense signaling components impair infection by the ascomycete Macrophomina phaseolina

Soybean (Glycine max) infection by the charcoal rot (CR) ascomycete Macrophomina phaseolina is enhanced by the soybean cyst nematode (SCN) Heterodera glycines. We hypothesized that G. max genetic lines impairing infection by M. phaseolina would also limit H. glycines parasitism, leading to resistance. As a part of this M. phaseolina resistance process, the genetic line would express defense genes already proven to impair nematode parasitism. Using G. max[DT97-4290/PI 642055], exhibiting partial resistance to M. phaseolina, experiments show the genetic line also impairs H. glycines parasitism. Furthermore, comparative studies show G. max[DT97-4290/PI 642055] exhibits induced expression of the effector triggered immunity (ETI) gene NON-RACE SPECIFIC DISEASE RESISTANCE 1/HARPIN INDUCED1 (NDR1/HIN1) that functions in defense to H. glycines as compared to the H. glycines and M. phaseolina susceptible line G. max[Williams 82/PI 518671]. Other defense genes that are induced in G. max[DT97-4290/PI 642055] include the pathogen associated molecular pattern (PAMP) triggered immunity (PTI) genes ENHANCED DISEASE SUSCEPTIBILITY1 (EDS1), NONEXPRESSOR OF PR1 (NPR1) and TGA2. These observations link G. max defense processes that impede H. glycines parasitism to also potentially function toward impairing M. phaseolina pathogenicity. Testing this hypothesis, G. max[Williams 82/PI 518671] genetically engineered to experimentally induce GmNDR1-1, EDS1-2, NPR1-2 and TGA2-1 expression leads to impaired M. phaseolina pathogenicity. In contrast, G. max[DT97-4290/PI 642055] engineered to experimentally suppress the expression of GmNDR1-1, EDS1-2, NPR1-2 and TGA2-1 by RNA interference (RNAi) enhances M. phaseolina pathogenicity. The results show components of PTI and ETI impair both nematode and M. phaseolina pathogenicity.

Overexpression of OsCIPK30 Enhances Plant Tolerance to Rice stripe virus

Rice stripe virus (RSV) causes a severe disease in Oryza sativa (rice) in many Eastern Asian countries. The NS3 protein of RSV is a viral suppressor of RNA silencing, but plant host factors interacting with NS3 have not been reported yet. Here, we present evidence that expression of RSV NS3 in Arabidopsis thaliana causes developmental abnormalities. Through yeast two-hybrid screening and a luciferase complementation imaging assay, we demonstrate that RSV NS3 interacted with OsCIPK30, a CBL (calcineurin B-like proteins)-interaction protein kinase protein. Furthermore, OsCIPK30 was overexpressed to investigate the function of OsCIPK30 in rice. Our investigation showed that overexpression of OsCIPK30 in rice could delay the RSV symptoms and show milder RSV symptoms. In addition, the expression of pathogenesis-related genes was increased in OsCIPK30 transgenic rice. These results suggest that overexpression of OsCIPK30 positively regulates pathogenesis-related genes to enhance the tolerance to RSV in rice. Our findings provide new insight into the molecular mechanism underlying resistance to RSV disease.

Emerging Insights into the Functions of Pathogenesis-Related Protein 1

The members of the pathogenesis-related protein 1 (PR-1) family are among the most abundantly produced proteins in plants on pathogen attack, and PR-1 gene expression has long been used as a marker for salicylic acid-mediated disease resistance. However, despite considerable interest over several decades, their requirement and role in plant defence remains poorly understood. Recent reports have emerged demonstrating that PR-1 proteins possess sterol-binding activity, harbour an embedded defence signalling peptide, and are targeted by plant pathogens during host infection. These studies have re-energised the field and provided long-awaited insights into a possible PR-1 function. Here we review the current status of PR-1 proteins and discuss how these recent advances shed light on putative roles for these enigmatic proteins.

Molecular Cloning of HbPR-1 Gene from Rubber Tree, Expression of HbPR-1 Gene in Nicotiana benthamiana and Its Inhibition of Phytophthora palmivora

This is the first report to present a full-length cDNA (designated HbPR-1) encoding a putative basic HbPR-1 protein from rubber tree (Hevea brasiliensis) treated with salicylic acid. It was characterized and also expressed in Nicotiana benthamiana using Agrobacterium-mediated transient gene expression system in order to investigate the role of HbPR-1 gene in rubber tree against its oomycete pathogen Phytopthora palmivora and to produce recombinant HbPR-1 protein for microbial inhibition test. The HbPR-1 cDNA was 647 bp long and contained an open reading frame of 492 nucleotides encoding 163 amino acid residues with a predicted molecular mass of 17,681 Da and an isoelectric point (pI) of 8.56, demonstrating that HbPR-1 protein belongs to the basic PR-1 type. The predicted 3D structure of HbPR-1 was composed of four α-helices, three β-sheets, seven strands, and one junction loop. Expression and purification of recombinant HbPR-1 protein were successful using Agrobacterium-mediated transient expression and one-step of affinity chromatography. Heterologous expression of HbPR-1 in N. benthamiana reduced necrosis areas which were inoculated with P. palmivora zoospores, indicating that the expressed HbPR-1 protein played an important role in plant resistance to pathogens. The purified recombinant HbPR-1 protein was found to inhibit 64% of P. palmivora zoospore germination on a water agar plate compared with control, suggesting that it was an antimicrobial protein against P. palmivora.