Expression Of Pathogenesis-related Genes Research Articles

Transcriptome profiling reveals the underlying mechanism of grape post-harvest pathogen Penicillium olsonii against the metabolites of Bacillus velezensis.

Pathogen infection influences the post-harvest shelf life of grape berries. In a preliminary study, metabolites produced by Bacillus velezensis significantly inhibited the growth of the grape postharvest pathogen Penicillium olsonii. To investigate the mechanism of interaction between B. velezensis and P. olsonii, a draft genome was generated for P. olsonii WHG5 using the Illumina NovaSeq platform, and the transcriptomic changes in WHG5 were analyzed in response to the exposure to B. velezensis metabolites (10% v/v). The expression levels of genes associated with sporulation, including GCY1, brlA, and abaA, were down-regulated compared with those of the control. In addition, spore deformation and abnormal swelling of the conidiophore were observed. The expression of crucial enzymes, including fructose 2,6-bisphosphate and mannitol-2-dehydrogenase, was down-regulated, indicating that the glycolytic pathway of WHG5 was adversely affected by B. velezensis metabolites. The KEGG pathway enrichment analysis revealed that glutathione metabolism and the antioxidant enzyme system were involved in the response to B. velezensis metabolites. The down-regulation of the pathogenesis-related genes, PG1 and POT1, suggested that B. velezensis metabolites decreased the pathogenicity of P. olsonii. B. velezensis metabolites disrupted the homeostasis of reactive oxygen species in P. olsonii by affecting glucose metabolism, resulting in spore deformation and disruption of growth. In addition, the expression of key pathogenesis-related genes was down-regulated, thereby reducing the pathogenicity of P. olsonii. This study provides insights into the responses of P. olsonii to B. velezensis metabolites and identifies potential target genes that may be useful in biocontrol strategies for the suppression of post-harvest spoilage in grapes.

Transcription factor CsERF1B regulates postharvest citrus fruit resistance to Penicillium digitatum

Green mold, caused by Penicillium digitatum (P. digitatum), is among the most important postharvest disease of citrus fruit in terms of economic losses. Previous studies reported that AP2/ERFs in citrus pericarp positively respond to P. digitatum infection; therefore, it is presumed that AP2/ERFs could participate in the regulation of the fruit resistance response. However, limited research is available on AP2/ERF transcription factors in regulating the disease resistance of citrus fruit. In the present study, the regulatory role of CsERF1B in citrus green mold was clarified and the regulatory mechanism was initially explored. In our work, CsERF1B is a transcriptional activator with a nuclear localization signal. Transient overexpression of CsERF1B in citrus pericarp significantly enhanced fruit resistance to green mold and induced upregulated expression of pathogenesis-related genes in the pericarp. CsERF1B directly activated lignin synthesis genes, increased the activities of related enzymes, and promoted the accumulation of lignin. CsERF1B directly activated the genes related to jasmonic acid signaling and immunity, indirectly activated genes related to chitinase, and it also directly repressed salicylic acid signaling pathway genes, thus participating in the regulation of fruit disease resistance. This research provides novel insights into the mechanisms of disease resistance regulation by AP2/ERF transcription factors in citrus fruit.

Potato calcineurin B-like protein CBL4, interacting with calcineurin B-like protein-interacting protein kinase CIPK2, positively regulates plant resistance to stem canker caused by Rhizoctonia solani.

Calcium sensor calcineurin B-like proteins (CBLs) and their interacting partners, CBL-interacting protein kinases (CIPKs), have emerged as a complex network in response to abiotic and biotic stress perception. However, little is known about how CBL-CIPK complexes function in potatoes. In this study, we identified the components of one potato signaling complex, StCBL4-StCIPK2, and characterized its function in defense against Rhizoctonia solani causing stem canker in potato. Expressions of both StCBL4 and StCIPK2 from potato were coordinately induced upon R. solani infection and following exposure to the defense genes. Furthermore, transient overexpression of StCBL4 and StCIPK2 individually and synergistically increased the tolerance of potato plants to R. solani in Nicotiana benthamiana. Additionally, the transgenic potato has also been shown to enhance resistance significantly. In contrast, susceptibility to R. solani was exhibited in N. benthamiana following virus-induced gene silencing of NbCBL and NbCIPK2. Evidence revealed that StCBL4 could interact in yeast and in planta with StCIPK2. StCBL4 and StCIPK2 transcription was induced upon R. solani infection and this expression in response to the pathogen was enhanced in StCBL4- and StCIPK2-transgenic potato. Moreover, accumulated expression of pathogenesis-related (PR) genes and reactive oxygen species (ROS) was significantly upregulated and enhanced in both StCBL4- and StCIPK2- transgenic potato. Accordingly, StCBL4 and StCIPK2 were involved in regulating the immune response to defend the potato plant against R. solani. Together, our data demonstrate that StCBL4 functions in concert with StCIPK2, as positive regulators of immunity, contributing to combating stem canker disease in potato.

Studies on the Requirement of Transthyretin Protein (BxTTR-52) for the Suppression of Host Innate Immunity in Bursaphelenchus xylophilus

The pinewood nematode, Bursaphelenchus xylophilus, has been determined as one of the world's top ten plant-parasitic nematodes. It causes pine wilt, a progressive disease that affects the economy and ecologically sustainable development in East Asia. B. xylophilus secretes pathogenic proteins into host plant tissues to promote infection. However, little is known about the interaction between B. xylophilus and pines. Previous studies reported transthyretin proteins in some species and their strong correlation with immune evasion, which has also been poorly studied in B. xylophilus. In this study, we cloned and functionally validated the B. xylophilus pathogenic protein BxTTR-52, containing a transthyretin domain. An in situ hybridization assay demonstrated that BxTTR-52 was expressed mainly in the esophageal glands of B. xylophilus. Confocal microscopy revealed that BxTTR-52-RFP localized to the nucleus, cytoplasm, and plasma membrane. BxTTR-52 recombinant proteins produced by Escherichia coli could be suppressed by hydrogen peroxide and antioxidant enzymes in pines. Moreover, silencing BxTTR-52 significantly attenuated the morbidity of Pinus thunbergii infected with B. xylophilus. It also suppressed the expression of pathogenesis-related genes in P. thunbergii. These results suggest that BxTTR-52 suppresses the plant immune response in the host pines and might contribute to the pathogenicity of B. xylophilus in the early infection stages.

A plant growth-promoting bacteria Priestia megaterium JR48 induces plant resistance to the crucifer black rot via a salicylic acid-dependent signaling pathway.

Xanthomonas campestris pv. campestris (Xcc)-induced black rot is one of the most serious diseases in cruciferous plants. Using beneficial microbes to control this disease is promising. In our preliminary work, we isolated a bacterial strain (JR48) from a vegetable field. Here, we confirmed the plant-growth-promoting (PGP) effects of JR48 in planta, and identified JR48 as a Priestia megaterium strain. We found that JR48 was able to induce plant resistance to Xcc and prime plant defense responses including hydrogen peroxide (H2O2) accumulation and callose deposition with elevated expression of defense-related genes. Further, JR48 promoted lignin biosynthesis and raised accumulation of frees salicylic acid (SA) as well as expression of pathogenesis-related (PR) genes. Finally, we confirmed that JR48-induced plant resistance and defense responses requires SA signaling pathway. Together, our results revealed that JR48 promotes plant growth and induces plant resistance to the crucifer black rot probably through reinforcing SA accumulation and response, highlighting its potential as a novel biocontrol agent in the future.

Endophytic Bacillus subtilis antagonize soil-borne fungal pathogens and suppress wilt complex disease in chickpea plants (Cicer arietinum L.).

The present study aimed to identify potential endophytic bacteria antagonistic against three soil-borne fungal pathogens, Rhizoctonia solani, Sclerotium rolfsii, and Fusarium oxysporum f.sp. ciceri causing root rot, collar rot, and fungal wilt diseases in chickpea plants, respectively. A total of 255 bacterial endophytes were isolated from the leaves, stems, and roots of seven different crop plants (chickpea, tomato, wheat, berseem, mustard, potato, and green pea). The dual culture-based screening for antifungal properties indicated that three endophytic isolates had strong inhibition (>50%) against all three pathogens tested. Based on morphological, biochemical, and molecular characterization, the selected isolates (TRO4, CLO5, and PLO3) were identified as different strains of Bacillus subtilis. The bacterial endophytes (TRO4 and CLO5) were positive for plant growth promoting (PGP) traits viz., ammonia, siderophore, and indole-3-acetic acid (IAA) production. The bio-efficacy of the endophytes (TRO4, CLO5, and PLO3) was tested by an in planta trial in chickpea pre-challenged with R. solani, S. rolfsii, and F. oxysporum f.sp. ciceri. The B. subtilis strains TRO4 and CLO5 were found to be effective in reducing percent disease incidence (p ≤ 0.05) and enhancing plant growth parameters. The different root parameters viz. root length (mm), surface area (cm2), root diameter (mm), and root volume (cm3) were significantly (p ≤ 0.05) increased in TRO4 and CLO5 inoculated chickpea plants. Confocal Scanning Laser Microscopy showed heavy colonization of bacteria in the roots of endophyte-inoculated chickpea plants. The inoculation of endophytic Bacillus subtilis strains TRO4 and CLO5 in chickpea plants through seed biopriming reduced the accumulation of superoxide, enhanced the plant defense enzymes, and induced the expression of Pathogenesis-Related (PR) genes. Semi-quantitative analysis of defense-related genes showed differential activation of PR genes (60srp and IFR) by endophyte inoculation. The results of the present study reveal the antagonistic potential of B. subtilis strains TRO4 and CLO5 against three major soil-borne fungal pathogens and their ability to suppress wilt complex disease in chickpea plants. This is the first report on the simultaneous suppression of three major soil-borne fungal pathogens causing wilt complex in chickpea plants by endophytic B. subtilis strains.

Methionine sulfoxide reductase B5 plays vital roles in tomato fruit defense response against Botrytis cinerea induced by methyl jasmonate

A methionine sulfoxide reductase (Msr) gene is identified in tomato fruit, and its protein’s identity as MsrB5 was determined by phylogenetic analysis and multiple sequence alignment. Correspondingly, the role of SlMsrB5 in methyl jasmonate (MeJA)-mediated defense to B. cinerea in tomato fruit was investigated by using 0.05 mM MeJA treatment on SlMsrB5-silenced fruit during storage. The results showed that MeJA treatment upregulated total phenols and flavonoids, disease resistance enzymes activities, and expression of pathogenesis-related (PR) genes, including SlPR1/2a/2b/3a/3b/STH2 in tomato fruit. Additionally, MeJA inhibited the increase of hydrogen peroxide and superoxide anions by improving antioxidant enzyme activities and the ascorbic acid-glutathione (ASA-GSH) cycle. Similarly, MeJA induced the accumulation of jasmonic acid and the transcriptions of its signal transduction-related genes (SlCOI1 and SlMYC2), which could lead to the transcription of disease response-related marker genes such as SlPI I and SlPI II. These MeJA-regulated changes may contribute to improved disease resistance in tomato fruit. However, SlMsrB5 silence reduced the effect of MeJA on the above parameters and caused severer disease occurrence in the SlMsrB5-silenced + MeJA treated group than in MeJA treated group, probably because the low levels of SlMsrB5 transcription could not restore the activity of defense and antioxidant-related enzymes. Furthermore, correlation analysis revealed that the above effects regulated by MeJA were highly correlated with SlMsrB5 transcript levels. Therefore, these findings provide insight on SlMsrB5's role in MeJA-mediated tomato immune responses to B. cinerea by regulating defensive enzymes and genes, antioxidant capacity, and the JA signaling pathway.

Prokaryotic expression, purification and activity analysis of necrosis and ethylene-inducing peptide 1 (Nep1)-like protein from <italic>Magnaporthe grisea</italic>

<p indent="0mm">Necrosis and ethylene-inducing peptide 1 (Nep1)-like proteins (NLPs) are kinds of secreted by a range of plant-associated microorganisms including bacteria, fungi, and oomycetes. The first member of NLP families is Nep1 protein isolated and purified from the culture filtrates of <italic>Fusarium oxysporum</italic> by Bailey in 1995. The protein induced ethylene and necrosis in leaves of a variety of dicotyledoneae but not in members of the monocotyledoneae tested. In addition, the Nep1 and some members of NLP family can also induce defense-related responses, including the expression of pathogenesis-related genes, callose deposition, accumulation of reactive oxygen species (ROS), and hypersensitive-like response in plants. Previous studies have shown that the Nep1 and some members of NLP family play dual roles in plant-pathogen interactions. They not only act as a cytolytic toxin that causes plasma membrane permeabilization and cytolysis in plant cells but also represent a class of microbial-associated molecular patterns (MAMPs) that trigger plant innate immune response. Many plant pathogen genomes contain different numbers and types of NLP family members. Different pathogens differ significantly in the number of NLP members, for example, the genome of <italic>Mycosphaerella graminicola</italic> contains only a single NLP homologue, whereas the number of NLP members in the genome of<italic> Phytophthora sojae</italic> and <italic>Phytophthora capsici</italic> up to 33 and 39, respectively. Recently, the NLP toxins are reported to target the plant cell-surface GIPC sphingolipids, and the difference in predominant GIPC series produced by the Eudicot and monocot determine host selectivity of microbial NLP cytolysins. However, recently, some NLP toxins produced by the pathogen of monocot were also proved to have cytotoxic activity on various monocot plant species and legitimize their presence in monocot-specific plant pathogens. The<italic> Magnaporthe grisea</italic>, causal agent of rice blast disease, contains four NPP1 domain-containing gene (MoNLP) in the fully sequenced genome. Although they are all highly induced during the infection of rice, the quadruple ΔMoNLP <italic>M</italic>.<italic>griseae</italic> mutant strains do not compromise its virulence. Therefore, the function and significance of their presence are still largely unknown. To further explore the potential function of these NLP members during the interactions between rice and <italic>Magnaporthe oryzae</italic> as well as the possibility that they may act as potential plant immunity inducers to modulate the plant immune response, the coding region sequences were cloned and ligated into the pGEX-6P-1 vector to prokaryotically express and purify these proteins by analyzing their sequence through bioinformatics methods. The results indicated that the solubility of prokaryotically expressed protein decreased obviously with the induction temperature increasing, but the expressed recombinant protein also increased. These corresponding purified and soluble proteins were then further infiltrated into the leaves of tobacco, indicated that the MoNLP1 and MoNLP4 fused with N-terminal GST tag were bioactive and induced the obvious leaf tissue necrosis of tobacco. However, the purified GST-MoNLP2 protein did not induce tissue necrosis in tobacco leaves, which may be due to expressed fusion protein with unexcised signal peptide or low protein concentration for injection. Our study laid a foundation for further investigating the function of this gene family in rice blast fungus and exploiting more potential protein elicitors for plants.

Chitosan-Salicylic acid and Zinc sulphate nano-formulations defend against yellow rust in wheat by activating pathogenesis-related genes and enzymes

Stripe rust instigated by Puccinia striiformis f. sp. tritici causes major yield loss in wheat. In this study, disease resistance was induced in wheat by pre-activation of pathogenesis related (PR) genes using two different nano-formulations (NFs) i.e. Chitosan- Salicylic acid (SA) NFs (CH-NFs) and Zinc sulphate NFs (Zn-NFs). These NFs were synthesized using green approach and were characterized using various techniques. Both NFs effectively controlled stripe rust in wheat genotypes (WH 711 and WH 1123) by significantly increasing activities of phenylalanine ammonia lyase, tyrosine ammonia lyase and polyphenol oxidase enzymes when compared with disease free-control and diseased plants. Total soluble sugar (TSS) level was highest in CH–NF treated plants. TSS was also relatively higher in diseased plants than disease free-control as well as Zn–NF treated plants. Both CH-NFs and Zn-NFs induced the expression of PR genes. In CH–NF treated plants, the relative expression of PR genes was higher on the 3rd day after spraying (DAS) of NFs as compared to diseased and Zn–NF treated plants in both the genotypes. While in case of Zn–NF treated plants, relative expression of PR genes was higher on 5th DAS as compared to diseased and disease free-control plants. Early rise in expression of PR genes due to NF treatments was responsible for disease resistance in both the wheat genotypes as evidenced by a lower average coefficient of infection. These NFs can be synthesized easily with low cost input, are eco-friendly and can be effectively used against yellow rust as well as other wheat diseases.

Overexpression of durum wheat NAC transcription factor TtNTL3A promotes early flowering and increases multiple stress tolerance in transgenic Arabidopsis

Plant-specific NAC transcription factors play important roles in plant development processes, hormone signaling and response to biotic and abiotic stresses. Here, a newly identified membrane-bound NAC gene, designated as TtNTL3A, was isolated from durum wheat. TtNTL3A was homologous to bread wheat TaNAC8 and rice OsNAC8. Moreover, yeast trans-activation assays revealed that TtNTL3A is a transcriptional activator. TtNTL3A was highly expressed in developing seeds and was induced by abiotic stresses, abscisic acid treatment and the infection with Fusarium graminearum. Besides, Transgenic Arabidopsis overexpressing TtNTL3A showed early flowering phenotype and higher tolerance to salt and drought stresses. RT-qPCR analysis revealed that drought and salt-responsive genes were highly expressed in transgenic lines compared to WT plants. Besides, these lines showed resistance to Fusarium graminearum, which was accompanied by a higher expression of pathogenesis-related genes (AtPR-1, Atpdf1.2, and AtNPR1) in TtNTL3A-OE lines. These findings suggest that TtNTL3A is an interesting target of genetic engineering to improve wheat tolerance to biotic and abiotic stresses.

SnRK1A-mediated phosphorylation of a cytosolic ATPase positively regulates rice innate immunity and is inhibited by Ustilaginoidea virens effector SCRE1.

Rice false smut caused by Ustilaginoidea virens is becoming one of the most recalcitrant rice diseases worldwide. However, the molecular mechanisms underlying rice immunity against U. virens remain unknown. Using genetic, biochemical and disease resistance assays, we demonstrated that the xb24 knockout lines generated in non-Xa21 rice background exhibit an enhanced susceptibility to the fungal pathogens U. virens and Magnaporthe oryzae. Consistently, flg22- and chitin-induced oxidative burst and expression of pathogenesis-related genes in the xb24 knockout lines were greatly attenuated. As a central mediator of energy signaling, SnRK1A interacts with and phosphorylates XB24 at Thr83 residue to promote ATPase activity. SnRK1A is activated by pathogen-associated molecular patterns and positively regulates plant immune responses and disease resistance. Furthermore, the virulence effector SCRE1 in U. virens targets host ATPase XB24. The interaction inhibits ATPase activity of XB24 by blocking ATP binding to XB24. Meanwhile, SCRE1 outcompetes SnRK1A for XB24 binding, and thereby suppresses SnRK1A-mediated phosphorylation and ATPase activity of XB24. Our results indicate that the conserved SnRK1A-XB24 module in multiple crop plants positively contributes to plant immunity and uncover an unidentified molecular strategy to promote infection in U. virens and a novel host target in fungal pathogenesis.

Volatile Dimethyl Disulfide from Guava Plants Regulate Developmental Performance of Asian Citrus Psyllid through Activation of Defense Responses in Neighboring Orange Plants.

Intercropping with guava (Psidium guajava L.) can assist with the management of Asian citrus psyllid (ACP, Diaphorina citri Kuwayama), the insect vector of the huanglongbing pathogen, in citrus orchards. Sulfur volatiles have a repellent activity and physiological effects, as well as being important components of guava volatiles. In this study, we tested whether the sulfur volatiles emitted by guava plants play a role in plant–plant communications and trigger anti-herbivore activities against ACP in sweet orange plants (Citrus sinensis L. Osbeck). Real-time determination using a proton-transfer-reaction mass spectrometer (PTR-MS) showed that guava plants continuously release methanethiol, dimethyl sulfide (DMS), and dimethyl disulfide (DMDS), and the contents increased rapidly after mechanical damage. The exposure of orange plants to DMDS resulted in the suppression of the developmental performance of ACP. The differential elevation of salicylic acid (SA) levels; the expression of phenylalanine ammonia lyase (PAL), salicylate-O-methyl transferase (SMT), and pathogenesis-related (PR1) genes; the activities of defense-related enzymes PAL, polyphenol oxidase (PPO), and peroxidase (POD); and the total polyphenol content were observed in DMDS-exposed orange plants. The emission of volatiles including myrcene, nonanal, decanal, and methyl salicylate (MeSA) was increased. In addition, phenylpropanoid and flavonoid biosynthesis, and aromatic amino acid (such as phenylalanine, tyrosine, and tryptophan) metabolic pathways were induced. Altogether, our results indicated that DMDS from guava plants can activate defense responses in eavesdropping orange plants and boost their herbivore resistance to ACP, which suggests the possibility of using DMDS as a novel approach for the management of ACP in citrus orchards.

Lipopeptides from Bacillus mojavensis I4 confer induced tolerance toward Rhizoctonia solani in potato (Solanum tuberosum)

Bacterial lipopeptides are known for their protective activity against plant pathogens. The antifungal activity of I4 lipopeptide was confirmed in vitro by a growth inhibition assay. In fact, the mycelium growth inhibition of R. solani in the presence of 5 mg/ml of I4 biosurfactants was about 76%. In this study, the protective effect of lipopeptides from Bacillus mojavensis I4 was tested in vitro against Rhizoctonia solani in potato plants. The treatment of potato plants with I4 lipopeptides (5 mg/ml), previously inoculated with 102 CFU/ml of R. solani was carried out for 15 days. Different physiological parameters such as plant morphology and growth, plant elongation, and chlorophyll content were higher in the inoculated and treated plants (IT) than in the inoculated untreated ones (IUT). Indeed, after 10 days of treatment, the application of I4 lipopeptide under biotic stress enhanced plant elongation and chlorophyll content by 75% and 65%, respectively, compared to the inoculated untreated plants (IUT). Moreover, the application of I4 lipopeptide biosurfactant under biotic stress caused a decrease in hydrogen peroxide (H2O2), malondialdehyde content (MDA) and enzymatic antioxidants activities (SOD, CAT and GPX) compared to untreated plants under the same conditions. Besides, The I4 lipopeptide treatment induced the expression of PR (pathogenesis-related) genes under control and biotic stress conditions and reduced plant diseases. Considered together, the data presented in this study demonstrated that biosurfactants produced by B. mojavensis I4 can be used to improve the biological control of potato pathogens.

Salicylic acid-activated BIN2 phosphorylation of TGA3 promotes ArabidopsisPR gene expression and disease resistance.

The plant defense hormone, salicylic acid (SA), plays essential roles in immunity and systemic acquired resistance. Salicylic acid induced by the pathogen is perceived by the receptor nonexpressor of pathogenesis-related genes 1 (NPR1), which is recruited by TGA transcription factors to induce the expression of pathogenesis-related (PR) genes. However, the mechanism by which post-translational modifications affect TGA's transcriptional activity by salicylic acid signaling/pathogen infection is not well-established. Here, we report that the loss-of-function mutant of brassinosteroid insensitive2 (BIN2) and its homologs, bin2-3 bil1 bil2, causes impaired pathogen resistance and insensitivity to SA-induced PR gene expression, whereas the gain-of-function mutant, bin2-1, exhibited enhanced SA signaling and immunity against the pathogen. Our results demonstrate that salicylic acid activates BIN2 kinase, which in turn phosphorylates TGA3 at Ser33 to enhance TGA3 DNA binding ability and NPR1-TGA3 complex formation, leading to the activation of PR gene expression. These findings implicate BIN2 as a new component of salicylic acid signaling, functioning as a key node in balancing brassinosteroid-mediated plant growth and SA-induced immunity.

The key molecular pattern BxCDP1 of Bursaphelenchus xylophilus induces plant immunity and enhances plant defense response via two small peptide regions.

The migratory plant-parasitic nematode Bursaphelenchus xylophilus is the pathogen of the pine wilt disease (PWD), causing serious damage to pine forests in China. During the process of plant resistance to multiple pathogens, plant immunity plays a key role. In this current study, the pathogen-associated molecular pattern (PAMP) BxCDP1 in B. xylophilus has been identified, but the host target protein of BxCDP1 and its key amino acid region inducing the plant immunity have yet to be elucidated. We found that BxCDP1 could trigger superoxide production, H2O2 production, and callose deposits. A RING-H2 finger protein 1 (RHF1) of Pinus thunbergii was screened and characterized as a target protein of BxCDP1 by yeast two-hybrid and co-immunoprecipitation (Co-IP). Moreover, two peptides (namely M9 and M16) proved to be key regions of BxCDP1 to induce PAMP-triggered immunity (PTI) in Nicotiana benthamiana, which also induced the expression of pathogenesis-related (PR) genes (PtPR-3, PtPR-4, and PtPR-5) in P. thunbergii and enhanced the resistance of the host to B. xylophilus. These results indicate that BxCDP1 plays a critical role in the interaction between B. xylophilus and P. thunbergii, and both peptides M9 and M16 have the potential to be developed and utilized as immune inducers of pines against B. xylophilus in future.

Role of elicitors to initiate the induction of systemic resistance in plants to biotic stress

Biotic stress affects crop yield and production. It is essential to acquire the knowledge necessary for designing resistance in host plants by understanding the interaction between pathogens and the host. Salicylic acid and jasmonic acid are principal regulators of interconnected signaling pathways of plant defense mechanisms to overcome stress conditions. Plants on pathogen attack experience transient increase in the reactive oxygen species production which in turn activates local programmed cell death and confers systemic resistance. Disease management is largely done by chemical compounds like fungicides, insecticides, and herbicides. However, these chemicals are hazardous to the environment and living beings hence it is necessary to search for novel harmless means of disease control. Elicitors are molecules that initiate systemic acquired resistance or induced systemic resistance in the host by inducing the expression of pathogenesis-related genes and protecting plants from diseases. This review discusses biotic stress, elicitors, and elicitor-receptor mediated defense mechanism acquired for systemic resistance and in this context, it attempts to draw the attention of the researchers to find novel elicitors as disease control alternatives.

Deletion of Diterpenoid Biosynthetic Genes CYP76M7 and CYP76M8 Induces Cell Death and Enhances Bacterial Blight Resistance in Indica Rice '9311'.

Lesion mimic mutants (LMMs) are ideal materials for studying cell death and resistance mechanisms. Here, we identified and mapped a novel rice LMM, g380. The g380 exhibits a spontaneous hypersensitive response-like cell death phenotype accompanied by excessive accumulation of reactive oxygen species (ROS) and upregulated expression of pathogenesis-related genes, as well as enhanced resistance to Xanthomonas oryzae pv. oryzae (Xoo). Using a map-based cloning strategy, a 184,916 bp deletion on chromosome 2 that overlaps with the diterpenoid biosynthetic gene cluster was identified in g380. Accordingly, the content of diterpenoids decreased in g380. In addition, lignin, one of the physical lines of plant defense, was increased in g380. RNA-seq analysis showed 590 significantly differentially expressed genes (DEG) between the wild-type 9311 and g380, 585 of which were upregulated in g380. Upregulated genes in g380 were mainly enriched in the monolignol biosynthesis branches of the phenylpropanoid biosynthesis pathway, the plant–pathogen interaction pathway and the phytoalexin-specialized diterpenoid biosynthesis pathway. Taken together, our results indicate that the diterpenoid biosynthetic gene cluster on chromosome 2 is involved in immune reprogramming, which in turn regulates cell death in rice.

Pathogenesis-Related Gene Expression in Response to Trachyspermum ammi Supplementation Along With Probiotics in Chicken Salmonellosis and Insights in Drug Therapeutics.

Salmonella enterica serovar typhimurium (S. typhimurium) is the leading cause of foodborne illness. Since Salmonella continues to have a detrimental effect on public health, there is an ongoing need to develop more advanced methods for combating Salmonellosis in foods before they reach consumers. In addition, the quest for alternative natural products has recently intensified due to increasingly stringent regulations regarding the use of antibiotics as growth promoters and consumer demand for antibiotic-free poultry products. This study evaluated the effect of Ajwain extract (AJE) on immune response and antioxidant status in broiler chicks challenged with Salmonella typhimurium. The chicks were infected with S. typhimurium and were divided into the different groups, except for the control group (CON). The challenged chicks received different treatments with 3 × 109 colony-forming unit (CFU) AciproTM-WS probiotic (PRO), 200 mg/kg Ajwain extract (AJE), 200 mg/100 kg of enrofloxacin (ENR), and a combination of 3 × 109 CFU AciproTM-WS probiotic and 200 mg/kg Ajwain extract (COM). Five days posttreatment, the tissue samples (liver and spleen) were analyzed. The results showed that basal diet supplemented with Ajwain extract (AJE) and a combination of probiotic and Ajwain extract (COM) significantly (P < 0.0.5) reduced the cytokine expression in broiler chicks challenged with S. typhimurium. Our findings suggest that AJE can clear the bacterial infection, improve antioxidant status, and suppress the inflammation response. Additionally, AJE supplementation significantly mitigated the S. typhimurium-induced increase in the interleukin-6 (IL-6) (liver and spleen), interleukin-8 (IL-8) (liver and spleen), interleukin-17A (IL-17A) (liver and spleen), and inducible nitric oxide (iNOS) (spleen and liver) levels (P < 0.05). We conclude that Ajwain is an efficient feed additive with antioxidant and anti-inflammatory properties. The interaction networks developed in this study provide a novel lead that could be targeted for anti-inflammatory and antioxidant properties.

Expression of PEI-coated gold nanoparticles carrying exogenous gene in periwinkle mesophyll cells and its practice in huanglongbing research

SummaryHuanglongbing (HLB) is a devastating disease of citrus, which is mostly caused by Candidatus Liberibacter asiaticus (CLas). To realize the specific application of nano-transgenic technology in HLB, AuNPs-PEI (Gold Nanoparticles-Polyethylenimine) was used to carry foreign genes into the leaves of periwinkle (Catharanthus roseus) by infiltration. Here, we demonstrated that NPR1-GFP protein expression was observed from the 12th hour to the 10th day after infiltrating AuNPs-PEI-pNPR1 (Arabidopsis thaliana nonexpressor of pathogenesis-related gene 1)-GFP. Fluorescence of mCherry was observed 6 h after AuNPs-PEI-pNLS (nuclear localization signal sequence)-mCherry infiltration and fluorescence of FAM was observed in the nucleus 4 h after AuNPs-PEI-FAM-siRNANPR1 infiltration. In addition, NPR1-GFP expression in CLas-infected periwinkle leaves was significantly higher than that in healthy periwinkle leaves after infiltration. Our work confirmed that the expression of exogenous NPR1-GFP could reduce the CLas titers by promoting the expression of PR (pathogenesis related) genes and ICS (isochorismate synthase) gene.

Functional studies of rice blast resistance related gene&amp;lt;italic&amp;gt; OsSAMS1&amp;lt;/italic&amp;gt;

<p id="C3">Rice blast is one of the most devastating diseases in rice, which causes great economic losses to agricultural production. It has been reported that <italic>S-Adenosyl-l-Mmethionine Synthetase</italic> 1 (<italic>OsSAMS1</italic>) is involved in the process of senescence in rice. Transcriptome sequencing analysis showed that the relative expression level of<italic> OsSAMS1</italic> was significantly increased after inoculation with <italic>Magnaporthe oryzae </italic>(<italic>M. oryzae</italic>). However, it remains unclear whether <italic>OsSAMS1</italic> is involved in rice immunity. To verify this, we constructed the knock-out mutants of <italic>OsSAMS1</italic> in the wild type variety ZH11. The results showed that <italic>OsSAMS1</italic> was mainly expressed in rice leaves, and its expression was significantly induced by <italic>M. oryzae</italic> inoculation. Subcellular localization revealed that OsSAMS1 was distributed in the plasma membrane, cytoplasm, and nucleus. Compared to the wild type, the two knockout mutants, <italic>ossams1-1</italic> and <italic>ossams1-2</italic>, displayed enhanced susceptibility upon <italic>M. oryzae</italic> infection, and the expression of pathogenesis-related (<italic>PR</italic>) genes was significantly inhibited. In addition, ethylene synthesis-related genes were also dramatically decreased in both two mutants. These results suggested that <italic>OsSAMS1</italic> was involved in rice immune response and positively regulated rice blast resistance, which lays a foundation for further revealing the molecular mechanism of <italic>OsSAMS1</italic> in plant immunity and provides genetic resources for rice breeding of blast resistance.